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1
Zhang, Kai. "Comparison of Flow Injection-MS/MS and LC-MS/MS for the Determination of Ochratoxin A." Toxins 13, no. 8 (August 6, 2021): 547. http://dx.doi.org/10.3390/toxins13080547.
Abstract:
Two methods for measuring ochratoxin A in corn, oat, and grape juice were developed and compared. Flow injection (FI) and on-line liquid chromatography (LC) performances were evaluated separately, with both methods using a triple quadrupole tandem mass spectrometer (MS/MS) for quantitation. Samples were fortified with 13C uniformly labeled ochratoxin A as the internal standard (13C-IS) and prepared by dilution and filtration, followed by FI- and LC-MS/MS analysis. For the LC-MS/MS method, which had a 10 min run time/sample, recoveries of ochratoxin A fortified at 1, 5, 20, and 100 ppb in corn, oat, red grape juice, and white grape juice ranged from 100% to 117% with RSDs < 9%. The analysis time of the FI-MS/MS method was <60 s/sample, however, the method could not detect ochratoxin A at the lowest fortification concentration, 1 ppb, in all tested matrix sources. At 5, 20, and 100 ppb, recoveries by FI-MS/MS ranged from 79 to 117% with RSDs < 15%. The FI-MS/MS method also had ~5× higher solvent and matrix-dependent instrument detection limits (0.12–0.35 ppb) compared to the LC-MS/MS method (0.02–0.06 ppb). In the analysis of incurred corn and oat samples, both methods generated comparable results within ±20% of reference values, however, the FI-MS/MS method failed to determine ochratoxin A in two incurred wheat flour samples due to co-eluted interferences due to the lack of chromatographic separation.
2
Ford, Roddey E., Mark J. Magera, Karen M. Kloke, Paul A. Chezick, Abdul Fauq, and Joseph P. McConnell. "Quantitative Measurement of Porphobilinogen in Urine by Stable-Isotope Dilution Liquid Chromatography-Tandem Mass Spectrometry." Clinical Chemistry 47, no. 9 (September 1, 2001): 1627–32. http://dx.doi.org/10.1093/clinchem/47.9.1627.
Abstract:
Abstract Background: Measurement of porphobilinogen (PBG) is useful in the diagnosis of the acute neurologic porphyrias. Currently used colorimetric assays lack analytical and clinical sensitivity and specificity. Methods: We developed a liquid chromatography-electrospray tandem mass spectrometry (LC-MS/MS) method for the measurement of PBG in 1 mL of urine, using 5-(aminoethyl)-4-(carboxymethyl) 1H-2,4-[13C]pyrolle-3-propanoic acid ([2,4-13C]PBG; 2.75 μg) as internal standard. After solid-phase extraction, LC-MS/MS analysis was performed in the selected-reaction monitoring (SRM) mode. PBG and [2,4-13C]PBG were monitored through their own precursor and product ion settings (m/z 227 to 210 and m/z 229 to 212, respectively). The retention time of PBG and [2,4-13C]PBG was 1.0 min in a 2.3-min analysis. Results: Daily calibrations (n = 6) between 0.1 and 2.0 mg/L were linear and reproducible. Inter- and intraassay CVs were 3.2–3.5% and 2.6–3.1%, respectively, at mean concentrations of 0.24, 1.18, and 2.15 mg/L. The regression equation for the comparison between an anion-exchange column method (y) and the LC-MS/MS method (x) was: y = 0.84x + 0.74 (Sy|x = 5.8 mg/24 h; r = 0.85; n = 100). In 47 volunteers, PBG excretion was 0.02–0.42 mg/24 h, lower than reported reference intervals (up to 2.0 mg/24 h) based on colorimetric methods. In 85 samples with PBG ≤0.5 by LC-MS/MS, 8 (9.4%) had values ≥2.0 mg/24 h by the anion-exchange method (mean ± SD, 4.3 ± 1.8 mg/24 h). In 11 patients with confirmed diagnoses of acute porphyria and increased PBG by LC-MS/MS, 2 had values within the reported reference intervals by a quantitative anion-exchange method. Conclusions: The quantitative LC-MS/MS method for PBG measurement exhibits greater analytical specificity and improved clinical sensitivity and specificity than currently available methods.
3
Trilleras, Jorge, Karen Feria, Daniel Alcazar, Jairo Quiroga, Manuel Nogueras, and Justo Cobo. "Síntesis multicomponente y caracterización de derivados pirimido [4,5-b] quinolínicos con evaluación de la actividad antileishmania." Revista Colombiana de Ciencias Químico-Farmacéuticas 46, no. 1 (January 1, 2017): 5–17. http://dx.doi.org/10.15446/rcciquifa.v46n1.67286.
Abstract:
A partir de 6-amino-3-metil-2-(metiltio)pirimidin-4(3H)-ona, aldehídos aromáticos y benzoquinona, por medio de una reacción de ciclodeshidratación de Michael asistida por radiación de microondas, se realizó la síntesis y caracterización de la serie de derivados tricomponentes pirimido[4,5-b]quinolínicos, y se evaluó la posible actividad antileishmania. Los nuevos compuestos se caracterizaron por análisis espectroscópico de IR, RMN 1H, RMN 13C y MS.
4
Cocuron, Jean-Christophe, Zacchary Ross, and Ana P. Alonso. "Liquid Chromatography Tandem Mass Spectrometry Quantification of 13C-Labeling in Sugars." Metabolites 10, no. 1 (January 10, 2020): 30. http://dx.doi.org/10.3390/metabo10010030.
Abstract:
Subcellular compartmentation has been challenging in plant 13C-metabolic flux analysis. Indeed, plant cells are highly compartmented: they contain vacuoles and plastids in addition to the regular organelles found in other eukaryotes. The distinction of reactions between compartments is possible when metabolites are synthesized in a particular compartment or by a unique pathway. Sucrose is an example of such a metabolite: it is specifically produced in the cytosol from glucose 6-phosphate (G6P) and fructose 6-phosphate (F6P). Therefore, determining the 13C-labeling in the fructosyl and glucosyl moieties of sucrose directly informs about the labeling of cytosolic F6P and G6P, respectively. To date, the most commonly used method to monitor sucrose labeling is by nuclear magnetic resonance, which requires substantial amounts of biological sample. This study describes a new methodology that accurately measures the labeling in free sugars using liquid chromatography tandem mass spectrometry (LC-MS/MS). For this purpose, maize embryos were pulsed with [U-13C]-fructose, intracellular sugars were extracted, and their time-course labeling was analyzed by LC-MS/MS. Additionally, extracts were enzymatically treated with hexokinase to remove the soluble hexoses, and then invertase to cleave sucrose into fructose and glucose. Finally, the labeling in the glucosyl and fructosyl moieties of sucrose was determined by LC-MS/MS.
5
Zhang, Kai, Chia-Ding Liao, Shristi Prakash, Michael Conway, and Hwei-Fang Cheng. "Interlaboratory Validation of a Stable Isotope Dilution and Liquid Chromatography Tandem Mass Spectrometry Method for the Determination of Aflatoxins in Milk, Milk-Based Infant Formula, and Feed." Journal of AOAC INTERNATIONAL 101, no. 3 (May 1, 2018): 677–85. http://dx.doi.org/10.5740/jaoacint.17-0341.
Abstract:
Abstract An interlaboratory study was conducted to evaluate stable isotope dilution and LC tandem MS (MS/MS) for the determination of aflatoxins B1, B2, G1, G2, and M1 (AFB1, AFB2, AFG1, AFG2, and AFM1) in milk, milk-based infant formula (formula), and feed. Samples were first fortified with five 13C uniformly labeled aflatoxins {[13C]–internal standard (IS)} corresponding to the five native aflatoxins, which were subsequently extracted with acetonitrile–water (50 + 50, v/v), followed by centrifugation, filtration, and LC-MS/MS analysis. In addition to certified milk powder and animal feed, the three participating laboratories also analyzed milk, formula, and feed fortified with the five aflatoxins at concentrations ranging from 0.5 to 50 ng/g. The majority of recoveries ranged from 80 to 120%, with RSDs < 20%. Method LOQs were determined by the three laboratories using the three sample matrixes in replicates (n = 8), and the determined LOQs of AFB1, AFB2, AFG1, AFG2, and AFM1 ranged from 0.1 to 0.91, 0.24 to 0.64, 0.28 to 1.52, 0.19 to 3.80, and 0.12 to 0.45 ng/g, respectively. For detected aflatoxins in the certified materials, all measured concentrations were within ±25% of the certified values. Using [13C]–IS eliminated the need for matrix-matched calibration standards for quantitation, simplified sample preparation, and achieved simultaneous identification and quantitation of the aflatoxins in a simple LC-MS/MS procedure.
6
Qasem, Rani J., Ibrahim K. Frah, Ahmad S. Aljada, and Faisal A. Sehli. "Bioanalysis of plasma acetate levels without derivatization by LC–MS/MS." Bioanalysis 13, no. 5 (March 2021): 373–86. http://dx.doi.org/10.4155/bio-2020-0294.
Abstract:
Background: The acetate ion has important physiological functions and important therapeutic applications. A rapid LC–MS/MS method is described to measure acetate ions in human plasma without chemical derivatization. Materials & methods: A 200 μl sample was spiked with the internal standard 1,2-13C-acetate and proteins precipitated with trichloroacetic acid. The supernatant was recovered and separated under acidic conditions on a C18-column. The eluent was alkalinized by post-column infusion of methanolic ammonium hydroxide. Acetate ions were monitored on a low resolution mass spectrometer in negative ion mode. Results: Method was validated for accuracy and precision with a lower limit of quantitation of 9.7 μM and linear dynamic range up to 339.6 μM. Conclusion: The method is open for analytical improvement and adapts with metabolomic and pharmacometabolomic studies on chemicals of similar nature.
7
Moriyasu, Takako, Keiko Minowa, Miho Sakamoto, Kiyoko Kishimoto, Hideo Kadoi, Jun'ichi Nakajima, Ken'ichiro Mori, shuzo Ogino, Haruhiko Fukaya, and Yasuo Shida. "Differentiation Between Sulfoaildenafil and Its Analogs." Journal of AOAC INTERNATIONAL 94, no. 6 (November 1, 2011): 1770–77. http://dx.doi.org/10.5740/jaoacint.10-425.
Abstract:
Abstract An analog of aildenafil, which is a potent and highly selective inhibitor of phosphodiesterase 5, was found in a dietary supplement marketed for enhancement of sexual function. The compound was isolated by silica gel column chromatography, and its structure was identified by means of 13C-NMR spectrometry, 1H-NMR spectrometry, high-resolution MS, and X-ray structure determination. The compound was identified to be sulfoaildenafil (other names: thioaildenafil, dimethyl sildenafil thione, and thiomethisosildenafil). Sulfoaildenafil is very similar to the compound thiohomosildenafil. As it is difficult to distinguish between them by LC-photodiode array detector analysis, ultra-performance LC (UPLC)/MS, ion trap LC/MS/MS (LC/IT-MS/MS), and GC/MS were performed. The mass spectra of thiohomosildenafil by UPLC/MS and LC/IT-MS/MS showed mass fragments of m/z 58, 72, and 355, and the mass spectrum by GC/MS showed mass fragments of m/z 56, 72, and 420. Some of these fragments had low intensities, but they were useful for distinguishing between the two compounds. The relationship between aildenafil (other names: dimethylsildenafil and methisosildenafil) and homosildenafil is similar to that between sulfoaildenafil and thiohomosildenafil. Therefore, these were also examined.
8
Grocholska, Paulina, and Remigiusz Bąchor. "Trends in the Hydrogen−Deuterium Exchange at the Carbon Centers. Preparation of Internal Standards for Quantitative Analysis by LC-MS." Molecules 26, no. 10 (May 18, 2021): 2989. http://dx.doi.org/10.3390/molecules26102989.
Abstract:
The application of internal standards in quantitative and qualitative bioanalysis is a commonly used procedure. They are usually isotopically labeled analogs of the analyte, used in quantitative LC-MS analysis. Usually, 2H, 13C, 15N and 18O isotopes are used. The synthesis of deuterated isotopologues is relatively inexpensive, however, due to the isotopic effect of deuterium and the lack of isotopologue co-elution, usually they are not considered as good internal standards for LC-MS quantification. On the other hand, the preparation of 13C, 15N and 18O containing standards of drugs and their metabolites requires a complicated multistep de novo synthesis, starting from the isotopically labeled substrates, which are usually expensive. Therefore, there is a strong need for the development of low-cost methods for isotope-labeled standard preparations for quantitative analysis by LC-MS. The presented review concentrates on the preparation of deuterium-labeled standards by hydrogen−deuterium exchange reactions at the carbon centers. Recent advances in the development of the methods of isotopologues preparation and their application in quantitative analysis by LC-MS are evaluated.
9
Li, Dan, Justin A. Steimling, Joseph D. Konschnik, Scott L. Grossman, and Ty W. Kahler. "Quantitation of Mycotoxins in Four Food Matrices Comparing Stable Isotope Dilution Assay (SIDA) with Matrix-Matched Calibration Methods by LC–MS/MS." Journal of AOAC International 102, no. 6 (November 1, 2019): 1673–80. http://dx.doi.org/10.5740/jaoacint.19-0028.
Abstract:
Background: Mycotoxins are big concerns in food safety. Analytical methods are important for the evaluation of mycotoxins in different food commodities. Objective: In this study, stable isotope dilution assay (SIDA) was compared with a matrix-matched calibration method for the quantification of mycotoxins in four different commercially available commodities and two reference materials. Methods: All samples were extracted with water–acetonitrile (50+50, v/v), followed by filtration and LC–tandem MS analysis. Results: SIDA calibration accuracies ranged from 78.6 to 112% with relative SDs (RSDs) ≤16% across all four matrices. The majority of the recoveries across all matrices ranged from 70 to 120% with RSDs <11%. Of the four mycotoxins in the reference materials analyzed, only three had 13C-internal standard (IS), whereas the fourth was quantified using a closely eluting 13C-IS for a different mycotoxin. Mycotoxins paired with their corresponding 13C-IS had accuracies >90%, whereas accuracies for the mismatched mycotoxin/13C-IS were <14%. Conclusions: When 13C-IS are not available, matrix-matched calibration was also evaluated as an alternative to quantitating target mycotoxins. The use of 13C-IS is the best way to dynamically account for prevalent matrix effects, but matrix matching provides a viable alternative. Highlights: The study compared SIDA and matrix-matched calibration methods in terms of recovery, efficiency, advantages, and limitations for LC-MS based mycotoxin analysis.
10
Zhang, Kai, Jon W. Wong, Zhengwei Jia, Marta Vaclavikova, Mary W. Trucksess, and Timothy H. Begley. "Screening Multimycotoxins in Food-Grade Gums by Stable Isotope Dilution and Liquid Chromatography/Tandem Mass Spectrometry." Journal of AOAC INTERNATIONAL 97, no. 3 (May 1, 2014): 889–95. http://dx.doi.org/10.5740/jaoacint.13-263.
Abstract:
Abstract Stable isotope dilution with LC/MS/MS was used to determine the following 11 mycotoxins in food grade gums: aflatoxins B1, B2, G1, and G2; deoxynivalenol; fumonisins B1, B2, and B3; ochratoxin A; T-2 toxin; and zearalenone. Samples were fortified with 11 [13C]-uniformly labeled internal standard ([13C]-IS) mycotoxins that corresponded to the 11 target mycotoxins and extracted by acetonitrile–water (4 + 1, v/v), followed by LC/MS/MS analysis. Mycotoxins were quantitated with the fortified [13C]-IS in each sample. The average recoveries of aflatoxins B1, B2, G1, and G2 (1, 5, and 25 μg/kg); deoxynivalenol and fumonisins B1, B2, and B3 (25, 100, and 500 μg/kg); and ochratoxin A, T-2 toxin, and zearalenone (10, 50, and 250 μg/kg) ranged from 84 to 117% with RSDs less than 20%. Method-dependent LOQs were from 0.1 (aflatoxin B1) to 25 μg/kg (fumonisin B3). Among 20 market samples, aflatoxin B1 (< LOQ) was detected in a Guar gum and a Tragacanth gum, and zearalenone (6 ± 0.6 μg/kg) was detected in a Xanthan gum. The detected mycotoxins were further confirmed by comparing their enhanced product ion spectra to those of reference standards. The single laboratory validated stable isotope dilution and LC/MS/MS method provides sufficient selectivity, sensitivity, accuracy, and reproducibility with a simple sample preparation to screen the 11 mycotoxins in gums.
11
Li, Dan, Justin A. Steimling, Joseph D. Konschnik, Scott L. Grossman, and Ty W. Kahler. "Quantitation of Mycotoxins in Four Food Matrices Comparing Stable Isotope Dilution Assay (SIDA) with Matrix-Matched Calibration Methods by LC–MS/MS." Journal of AOAC INTERNATIONAL 102, no. 6 (November 1, 2019): 1673–80. http://dx.doi.org/10.1093/jaoac/102.6.1673.
Abstract:
Abstract Background: Mycotoxins are big concerns in food safety. Analytical methods are important for the evaluation of mycotoxins in different food commodities. Objective: In this study, stable isotope dilution assay (SIDA) was compared with a matrix-matched calibration method for the quantification of mycotoxins in four different commercially available commodities and two reference materials. Methods: All samples were extracted with water–acetonitrile (50+50, v/v), followed by filtration and LC–tandem MS analysis. Results: SIDA calibration accuracies ranged from 78.6 to 112% with relative SDs (RSDs) ≤16% across all four matrices. The majority of the recoveries across all matrices ranged from 70 to 120% with RSDs <11%. Of the four mycotoxins in the reference materials analyzed, only three had 13C-internal standard (IS), whereas the fourth was quantified using a closely eluting 13C-IS for a different mycotoxin. Mycotoxins paired with their corresponding 13C-IS had accuracies >90%, whereas accuracies for the mismatched mycotoxin/13C-IS were <14%. Conclusions: When 13C-IS are not available, matrix-matched calibration was also evaluated as an alternative to quantitating target mycotoxins. The use of 13C-IS is the best way to dynamically account for prevalent matrix effects, but matrix matching provides a viable alternative. Highlights: The study compared SIDA and matrix-matched calibration methods in terms of recovery, efficiency, advantages, and limitations for LC-MS based mycotoxin analysis.
12
Blachnio-Zabielska, Agnieszka U., Piotr Zabielski, and Michael D. Jensen. "Intramyocellular diacylglycerol concentrations and [U-13C]palmitate isotopic enrichment measured by LC/MS/MS." Journal of Lipid Research 54, no. 6 (March 19, 2013): 1705–11. http://dx.doi.org/10.1194/jlr.d035006.
13
Fiby, Iris, Marta Magdalena Sopel, Herbert Michlmayr, Gerhard Adam, and Franz Berthiller. "Development and Validation of an LC-MS/MS Based Method for the Determination of Deoxynivalenol and Its Modified Forms in Maize." Toxins 13, no. 9 (August 27, 2021): 600. http://dx.doi.org/10.3390/toxins13090600.
Abstract:
The Fusarium mycotoxin deoxynivalenol (DON) is a common contaminant of cereals and is often co-occurring with its modified forms DON-3-glucoside (D3G), 3-acetyl-DON (3ADON) or 15-acetyl-DON (15ADON). A stable-isotope dilution liquid chromatography-tandem mass spectrometry (LC-MS/MS) based method for their determination in cereals was developed and validated for maize. Therefore, 13C-labelled D3G was enzymatically produced using 13C-DON and [13C6Glc]-sucrose and used as an internal standard (IS) for D3G, while uniformly 13C labelled IS was used for the other mycotoxins. Baseline separation was achieved for the critical peak pair DON/D3G, while 3ADON/15ADON could not be fully baseline separated after testing various reversed phase, fluorinated phase and chiral LC columns. After grinding, weighing and extracting the cereal samples, the raw extract was centrifuged and a mixture of the four 13C-labelled ISs was added directly in a microinsert vial. The subsequent analytical run took 7 min, followed by negative electrospray ionization and selected reaction monitoring on a triple quadrupole MS. Maize was used as a complex cereal model matrix for validation. The use of the IS corrected the occurring matrix effects efficiently from 76 to 98% for D3G, from 86 to 103% for DON, from 68 to 100% for 15ADON and from 63 to 96% for 3ADON.
14
Jankowski, C. K., M. R. Van Calsteren, N. Aychet, J. F. Dozol, C. Moulin, and C. Lamouroux. "Study of the nitration of di-n-octylcrown-6 calix[4]arene using LCMS, NMR, and molecular modelling." Canadian Journal of Chemistry 83, no. 8 (August 1, 2005): 1098–113. http://dx.doi.org/10.1139/v05-126.
Abstract:
The selective HNO3 nitration of di-n-octylcrown-6 calix[4]arene using different conditions, studied with LCMS and NMR (1H and 13C) spectroscopic techniques, lead to the identification of most of the expected nitro derivative isomeric compounds. The formation of these isomers under acidic and radiolytic conditions is discussed with the help of molecular modelling.Key words: calix crown compounds, nitration of calixarenes, NMR of isomeric nitrocalixarenes, LC-ESI-MS.
15
Çelebier, Mustafa, Tuba Reçber, Emirhan Nemutlu, and Sedef Kır. "Ultrafiltration-based Extraction and LC-MS/MS Quantification of Phenylalanine in Human Blood Sample for Metabolite Target Analysis." Current Pharmaceutical Analysis 17, no. 1 (November 23, 2020): 81–86. http://dx.doi.org/10.2174/1573412915666190715095300.
Abstract:
Background: Phenylalanine is a significant biomarker for various diseases like phenylketonuria, gastric cancers, and ischemic stroke according to recent studies. Methods: In the present study; a simple, sensitive, selective and novel analytical method was validated by using an ultrafiltration-based extraction and LC-MS/MS quantification of phenylalanine in human plasma using 13C phenylalanine heavy isotope. Amicon® Ultra Centrifugal Filter was used for ultrafiltration. Parameters affecting LC separation and MS/MS detection were investigated and optimized. Chromatographic separation was achieved on a Merck SeQuant ZIC-HILIC (100x4.6 mm, 5 μm) at a column temperature of 40°C using a mobile phase of mixture of acetonitrile containing 0.1% formic acid and water containing 0.1% formic acid (50:50 v/v) at a flow rate of 0.35 mL/min. The transitions m/z 167→121 for 13C phenylalanine, m/z 166→120 for phenylalanine itself were monitored using the MRM mode. Result: The assay was linear concentration range of 0.0025 μg/mL to 1.20 μg/mL (R2=0.999). The developed method was validated according to FDA guidelines. The method was found linear, sensitive, precise, accurate, and selective.
16
Loh, Tze Ping, Chung Shun Ho, Michaela F. Hartmann, Rosita Zakaria, Clara Wai Shan Lo, Sjoerd van den Berg, Yolanda B. de Rijke, et al. "Influence of isotopically labeled internal standards on quantification of serum/plasma 17α-hydroxyprogesterone (17OHP) by liquid chromatography mass spectrometry." Clinical Chemistry and Laboratory Medicine (CCLM) 58, no. 10 (September 25, 2020): 1731–39. http://dx.doi.org/10.1515/cclm-2020-0318.
Abstract:
AbstractObjectivesOur recent survey of 44 mass spectrometry laboratories across 17 countries identified variation in internal standard (IS) choice for the measurement of serum/plasma 17α-hydroxyprogesterone (17OHP) by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The choice of IS may contribute to inter-method variations. This study evaluated the effect of two common isotopically labeled IS on the quantification of 17OHP by LC-MS/MS.MethodsThree collaborating LC-MS/MS laboratories from Asia, Europe and Australia, who routinely measure serum 17OHP, compared two IS, (1) IsoSciences carbon-13 labeled 17OHP-[2,3,4-13C3], and (2) IsoSciences deuterated 17OHP-[2,2,4,6,6,21,21,21-2H]. This was performed as part of their routine patient runs using their respective laboratory standard operating procedure.ResultsThe three laboratories measured 99, 89, 95 independent samples, respectively (up to 100 nmol/L) using the 13C- and 2H-labeled IS. The slopes of the Passing-Bablok regression ranged 0.98–1.00 (all 95% confidence interval [CI] estimates included the line of identity), and intercept of <0.1 nmol/L. Average percentage differences of −0.04% to −5.4% were observed between the two IS materials, which were less than the optimal bias specification of 7% determined by biological variation, indicating no clinically significant difference. The results of 12 Royal College of Pathologists of Australasia Quality Assurance Programs (RCPAQAP) proficiency samples (1–40 nmol/L) measured by the laboratories were all within the RCPAQAP analytical performance specifications for both IS.ConclusionsOverall, the comparison between the results of 13C- and 2H-labeled IS for 17OHP showed good agreement, and show no clinically significant bias when incorporated into the LC-MS/MS methods employed in the collaborating laboratories.
17
Alshishani, Anas, Inas Hasan, Fatima Ghanayem, Sewar Al-khasawneh, D. F. Chowdhury, and Alaa Abu Dayah. "Rapid LC-MS/MS method for determination of scopolamine in human plasma." Pharmacia 69, no. 4 (December 6, 2022): 1035–40. http://dx.doi.org/10.3897/pharmacia.69.e94441.
Abstract:
Sensitive, simple, and fast LC-MS/MS method for the determination of Scopolamine in human plasma was developed and validated. Liquid-Liquid extraction technique was used for sample preparation. Cyano bonded phase column (150 × 4.6 mm, 5 µm) was used for the separation with an isocratic elution of ammonium format buffer:methanol (60:40) mobile phase at a flow rate of 1 ml.min-1 over 3.8 min run time. Scopolamine and [13C,2H3]-Scopolamine, as internal standard, were detected and quantified in positive ion mode via MRM at m/z 304/138 and m/z 308/142, respectively. The developed method was validated according to FDA and EMA guidelines. The standard calibration curve was linear over the concentration range of 3.03–315.76 pg.ml-1 (r2 = 0.999). The intra-day and inter-day precision was in the range 1.28–10.46% and accuracy 96.89–110.53%. The recovery of analyte and IS was 78.63% and 76.21%, respectively. Scopolamine in plasma was stable at benchtop (short term) for 18 h, in autosampler tray for 43 h, in instrumentation room for 43 h (post-preparative), after 4 freeze-thaw cycles (−70 °C), and 3 days in the freezer (−70 °C). The validated method was successfully applied to a bioequivalence study of scopolamine transdermal patch of 1 mg for 3 days for 16 healthy Jordanian volunteers.
18
Kim, Kyoung Soon, Youmie Park, Sanghyun Lee, Dong Cheul Moon, and Bak‐Kwang Kim. "Stability of 13C‐Urea/PEG Capsules by LC‐APCI‐MS." Journal of Liquid Chromatography & Related Technologies 26, no. 8 (April 2003): 1275–86. http://dx.doi.org/10.1081/jlc-120020110.
19
Fiadorwu, Joshua, Kiran Subedi, Daniel Todd, and Mufeed M. Basti. "Multipronged Approach to Profiling Metabolites in Beta vulgaris L. Dried Pulp Extracts Using Chromatography, NMR and Other Spectroscopy Methods." Foods 12, no. 18 (September 21, 2023): 3510. http://dx.doi.org/10.3390/foods12183510.
Abstract:
Beetroot (Beta vulgaris L.) is known for being a rich source of phytochemicals, minerals and vitamins. This study aims to show how the combination of extraction/chromatography/mass spectrometry and NMR offers an efficient way to profile metabolites in the extracts of beetroot. Such combination may lead to the identification of more nutritional or medicinal compounds in natural products, and it is essential for our ongoing investigation to study the selective adsorption/desorption of these metabolites’ on/off nanoparticles. The aqueous and organic extracts underwent analyses using UV-vis spectroscopy; GC-MS; LC-MS; 1H, 13C, 31P, TOCSY, HSQC, and selective TOCSY NMR experiments. Polar Extract: The two forms of betalain pigment were identified by UV-vis and LC MS. Fourteen amino acids, sucrose, and other compounds, among which is riboflavin, were identified by LC-MS. Two-dimensional TOCSY showed the spin coupling correlations corresponding to some of these compounds. The HSQC spectrum showed 1H/13C spin correlation in sucrose, confirming its high abundance in beetroot. Organic Extract: GC-MS data enabled the identification of several compounds including six fatty acid methyl esters (FAME) with higher than, on average, 90% similarity score. Selective TOCSY NMR data showed the spin coupling pattern corresponding to oleic, linoleic, and linolenic fatty acids. 31P NMR spectra indicate that phospholipids exist in both the organic and aqueous phase.
20
Branton, Alice, Mahendra Kumar Trivedi, Dahryn Trivedi, and Snehasis Jana. "Analysis of Isotopic Abundance Ratio of Consciousness Energy Healing Treated Metronidazole Using LC-MS and GC-MS Spectrometry." Journal of Advanced Pharmaceutical Science And Technology 2, no. 3 (November 24, 2020): 26–36. http://dx.doi.org/10.14302/issn.2328-0182.japst-20-3618.
Abstract:
Metronidazole is an antibiotic and useful for the antibacterial and antiprotozoal medication. This study was performed to investigate the impact of the Trivedi Effect®-Biofield Energy Healing Treatment on the structural properties and the isotopic abundance ratio of metronidazole using LC-MS and GC-MS spectroscopy. Metronidazole sample was divided into two parts, one part of metronidazole was considered as control (no Biofield Energy Treatment was provided), while the second part was treated with the Trivedi Effect®-Consciousness Energy Healing Treatment remotely by a renowned Biofield Energy Healer, Alice Branton and termed as a treated sample. The LC-MS spectra of both the samples of metronidazole at the retention time (Rt) 2.61 minutes exhibited the mass of the protonated molecular ion peak at m/z 172 M+H+ (calculated for C6H10N3O3+, 172.07). The LC-MS based isotopic abundance ratio of PM+1/PM (2H/1H or 13C/12C or 15N/214N or 17O/16O) in the treated metronidazole was significantly increased by 8.24% compared with the control sample. Thus,13C, 2H, 15N,and17O contributions from (C6H10N3O3)+ to m/z 173 in the treated sample were significantly increased compared with the control sample. The GC-MS based isotopic abundance ratio of PM+1/PM in the treated metronidazole was significantly increased by 5.92% compared with the control sample. Hence,13C, 2H, 15N, and217O contributions from (C6H9N3O3)+ to m/z 172 in the Biofield Energy Treated sample were significantly increased compared with the control sample. However, the isotopic abundance ratio of PM+2/PM in the treated metronidazole was significantly decreased by 18.2% compared with the control sample. Hence,18O contributions from (C6H9N3O3)+ to m/z 173 in the treated sample were significantly decreased compared with the control sample. The isotopic abundance ratio of PM+1/PM (2H/1H or 13C/12C or 15N/14N or 17O/16O) and PM+2/PM (18O/16O) in the treated metronidazole was significantly altered compared to the control sample. From the results, it can be hypothesized that the changes in isotopic abundance and mass peak intensities could be due to changes in nuclei possibly through the interference of neutrino particles via the Trivedi Effect® - Consciousness Energy Healing Treatment. The new form of treated metronidazole would be better designing novel pharmaceutical formulations that might offer better therapeutic response against bacterial and protozoal infection in the vagina (bacterial vaginosis), stomach (giardiasis, trichomoniasis, pseudomembranous colitis), joints (pelvic inflammatory disease), liver, skin, brain, and respiratory tract, aspiration pneumonia, rosacea, intra-abdominal infections, lung abscess, fungating wounds, periodontitis, amoebiasis, oral infections, etc.
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Trivedi, Dahryn, Mahendra Kumar Trivedi, Alice Branton, Gopal Nayak, and Snehasis Jana. "Evaluation of the Impact of Consciousness Energy Healing Treatment on the Isotopic Abundance Ratios (PM+1/PM and PM+2/PM) of Ofloxacin." Journal of New Developments in Chemistry 2, no. 3 (November 13, 2019): 49–58. http://dx.doi.org/10.14302/issn.2377-2549.jndc-19-3080.
Abstract:
Ofloxacin is a class of fluorinated quinolone antibiotics, useful against most of the Gram-positive and Gram-negative bacterial infections. This study was designed to investigate the impact of the Trivedi Effect®-Consciousness Energy Healing Treatment on the structural properties and the isotopic abundance ratio of ofloxacin using LC-MS and GC-MS spectroscopy. Ofloxacin sample was divided into control and treated parts. The control ofloxacin did not receive the Consciousness Energy Healing Treatment, while the treated ofloxacin receives the Consciousness Energy Healing Treatment remotely by a renowned Biofield Energy Healer, Dahryn Trivedi. The LC-ESI-MS spectra of both the samples of ofloxacin at the retention time 3.05 minutes exhibited the mass of the protonated molecular ion peak at m/z 362.17 M+H+ (calculated for C18H21FN3O4+, 362.15). The LC-MS based isotopic abundance ratio of PM+1/PM in the treated ofloxacin was significantly increased by 56.57% compared with the control sample. Thus,2H, 15N, 13C, and17O contributions from (C18H21FN3O4)+ to m/z 363.17 in the treated ofloxacin were considerably increased compared with the control sample. The GC-MS based isotopic abundance ratios of PM+1/PM and PM+2/PM in the treated ofloxacin was significantly increased by 9.53% and 12.94%, respectively compared with the control sample. Hence,2H, 15N, 13C, 17O, and 18O contributions from (C18H21FN3O4)+ to m/z 318 and 319 in the treated ofloxacin were significantly increased compared with the control sample. The LC-MS and GC-MS based isotopic abundance ratios of PM+1/PM (2H/1H or 15N/14N or 13C/12C or 17O/16O), and PM+2/PM (18O/16O) in the treated ofloxacin were considerably improved compared to the control sample. The increased isotopic abundance ratio of the treated ofloxacin would increase the chemical bond strength and increase the stability in the body. The new form of treated ofloxacin would be more stable compared to the control sample and would be very useful to design improved pharmaceutical formulations that might offer better therapeutic response against infections of the urethra and cervix, infectious diarrhoea, urinary tract infections, cellulitis, chronic bronchitis, pneumonia, prostatitis, multidrug-resistant tuberculosis, plague, otitis media, etc.
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Chen, Yuhong, Melissa R. Snyder, Yi Zhu, Linda J. Tostrud, Linda M. Benson, Jerry A. Katzmann, and H. Robert Bergen. "Simultaneous Phenotyping and Quantification of α-1-Antitrypsin by Liquid Chromatography–Tandem Mass Spectrometry." Clinical Chemistry 57, no. 8 (August 1, 2011): 1161–68. http://dx.doi.org/10.1373/clinchem.2011.163006.
Abstract:
BACKGROUND α-1-Antitrypsin (A1AT) deficiency results from a genetic disorder at 2 common loci. Diagnosis requires quantification of A1AT and subsequent identification of the specific variant. The current algorithm of laboratory testing for the diagnosis of A1AT deficiency uses a combination of quantification (nephelometry), genotyping, and/or phenotyping. We developed a multiple reaction monitoring liquid chromatography–tandem mass spectrometry (LC-MS/MS) method for simultaneous quantification of A1AT and identification of the 2 most common deficiency alleles present in 95% of the patients with A1AT deficiency. METHODS Serum samples (n = 40) were digested with trypsin, and appropriate 13C/15N-labeled standard peptides were added. We performed LC-MS/MS analysis with a 0.5- by 150-mm C18 column and H2O:acetonitrile:n-propanol:formic acid (A:98:1:1:0.2 and B:10:80:10:0.2; flow 12 μL/min) mobile phase in positive ion mode on a TSQ Quantum triple quadrupole MS system. We measured the A1AT concentration by comparison to a calibration curve and determined the phenotype by the presence or absence of variant peptides. We compared the results to the current phenotyping assay by isoelectric focusing (IEF) and the immunonephelometry quantitative assay. RESULTS For A1AT allele detection, in 39 of 40 samples the LC-MS/MS results were identical to those obtained by IEF gel electrophoresis. The single discrepant result was rerun by IEF at a lower dilution, and the results were in concordance. The A1AT quantification by LC-MS/MS also compared favorably with nephelometry. CONCLUSIONS The LC-MS/MS method correlates well with current phenotyping and nephelometric assays and has the potential to improve the laboratory diagnosis of genetic A1AT deficiency.
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Chen, Zhaohui, Michael P. Caulfield, Michael J. McPhaul, Richard E. Reitz, Steven W. Taylor, and Nigel J. Clarke. "Quantitative Insulin Analysis Using Liquid Chromatography–Tandem Mass Spectrometry in a High-Throughput Clinical Laboratory." Clinical Chemistry 59, no. 9 (September 1, 2013): 1349–56. http://dx.doi.org/10.1373/clinchem.2012.199794.
Abstract:
BACKGROUND Circulating insulin concentrations reflect the amount of endogenous insulin produced by the pancreas and can be monitored to check for insulin resistance. Insulin is commonly measured using immunochemiluminometric assays (ICMA). Unfortunately, differing crossreactivities of the various ICMA antibodies have led to variability in assay results. In contrast, liquid chromatography–tandem mass spectrometry (LC-MS/MS)-based approaches can provide a highly specific alternative to immunoassays. METHODS Insulin was extracted from patient serum and reduced to liberate the insulin B chain. Subsequent resolution of the peptide was achieved by LC coupled to triple-quadrupole MS. Selected-reaction monitoring of B-chain transitions was used for quantification. Recombinant human insulin was used as a calibrator and was compared against the National Institute for Biological Standards and Control (NIBSC) reference standard. Bovine insulin and a stable isotopic-labeled (13C/15N) human insulin B chain were used and compared as internal standards. RESULTS The LC-MS/MS assay described herein has been validated according to CLIA guidelines with a limit of detection of 1.8 μIU/mL (10.8 pmol/L) and a limit of quantitation of 3 μIU/mL (18.0 pmol/L). A correlation between the LC-MS/MS assay and a US Food and Drug Administration-approved ICMA was completed for patient samples and the resulting Deming regression revealed good agreement. A reference interval for the assay was established. CONCLUSIONS A simple, high-throughput, quantitative LC-MS/MS insulin assay traceable to the NIBSC standard has been successfully developed and validated.
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Trivedi, Dahryn, Mahendra Kumar Trivedi, Alice Branton, and Snehasis Jana. "Characterization of the Consciousness Energy Healing Treated Cholecalciferol Using LC-MS and GC-MS Spectrometry." Journal of Advanced Pharmaceutical Science And Technology 2, no. 4 (April 15, 2021): 40–50. http://dx.doi.org/10.14302/issn.2328-0182.japst-21-3772.
Abstract:
Vitamin D3 (cholecalciferol) is a fat-soluble vitamin, which widely used for the prevention and treatment rickets, osteoporosis, arthritis, Parkinson’s and Alzheimer’s diseases, autoimmune disease, dementia, glucose intolerance, etc. The impact of the Trivedi Effect®-Consciousness Energy Healing Treatment on the structural properties and the isotopic abundance ratio of cholecalciferol were evaluated using LC-MS and GC-MS spectroscopy. The test sample cholecalciferol was divided into control and treated parts. Only, the treated cholecalciferol was received the Trivedi Effect®-Consciousness Energy Healing Treatment remotely by a renowned Biofield Energy Healer, Dahryn Trivedi. The LC-MS spectra of both the samples at retention time (Rt) ~22 minutes exhibited the mass of the molecular ion peak at m/z 385.25 (calcd for C27H45O+, 385.35). The LC-MS based isotopic abundance ratio of PM+1/PM in the treated cholecalciferol was increased by 0.74% compared with the control sample. But, the GC-MS based isotopic abundance ratio of PM+1/PM and PM+2/PM in the treated cholecalciferol was significantly increased by 66.39% and 62.69%, respectively compared with the control sample. Hence,13C, 2H, 17O, and 18O contributions from C27H44O+ to m/z 386 and 387 in the treated cholecalciferol were significantly increased compared with the control sample. The isotopic abundance ratios of PM+1/PM (2H/1H or 13C/12C or 17O/16O) and PM+2/PM (18O/16O) in the treated cholecalciferol were significantly increased as compared to the control sample. The increased isotopic composition of the Trivedi Effect®-Consciousness Energy Healing Treated cholecalciferol might have altered the neutron to proton ratio in the nucleus via the possible mediation of neutrino. The increased isotopic abundance ratio of the treated cholecalciferol may increase the intra-atomic bond strength, increase its stability. The new form of cholecalciferol would be better designing novel pharmaceutical formulations that might be more stable and more efficacious for the prevention and treatment of various diseases such as vitamin D deficiency, rickets, osteoporosis, arthritis, multiple sclerosis, cancer, diabetes mellitus, mental disorders, cardiovascular diseases, hypertension, infections, influenza, cognitive impairment in older adults, Parkinson’s and Alzheimer’s diseases, autoimmune disease, dementia, glucose intolerance, multiple sclerosis, etc.
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Huang, He, Min Yuan, Phillip Seitzer, Susan Ludwigsen, and John M. Asara. "IsoSearch: An Untargeted and Unbiased Metabolite and Lipid Isotopomer Tracing Strategy from HR-LC-MS/MS Datasets." Methods and Protocols 3, no. 3 (July 30, 2020): 54. http://dx.doi.org/10.3390/mps3030054.
Abstract:
Stable isotopic tracer analysis is a technique used to determine carbon or nitrogen atom incorporation into biological systems. A number of mass spectrometry based approaches have been developed for this purpose, including high-resolution tandem mass spectrometry (HR-LC-MS/MS), selected reaction monitoring (SRM) and parallel reaction monitoring (PRM). We have developed an approach for analyzing untargeted metabolomic and lipidomic datasets using high-resolution mass spectrometry with polarity switching and implemented our approach in the open-source R script IsoSearch and in Scaffold Elements software. Using our strategy, which requires an unlabeled reference dataset and isotope labeled datasets across various biological conditions, we traced metabolic isotopomer alterations in breast cancer cells (MCF-7) treated with the metabolic drugs 2-deoxy-glucose, 6-aminonicotinamide, compound 968, and rapamycin. Metabolites and lipids were first identified by the commercial software Scaffold Elements and LipidSearch, then IsoSearch successfully profiled the 13C-isotopomers extracted metabolites and lipids from 13C-glucose labeled MCF-7 cells. The results interpreted known models, such as glycolysis and pentose phosphate pathway inhibition, but also helped to discover new metabolic/lipid flux patterns, including a reactive oxygen species (ROS) defense mechanism induced by 6AN and triglyceride accumulation in rapamycin treated cells. The results suggest the IsoSearch/Scaffold Elements platform is effective for studying metabolic tracer analysis in diseases, drug metabolism, and metabolic engineering for both polar metabolites and non-polar lipids.
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Bouajila, J., G. Raffin, H. Waton, C. Sanglar, J. O. Païsse, and M. F. Grenier-Loustalot. "Phenolic Resins (II) – Influence of the Chemical Structure of High Molecular Weight Molecules on the Mechanisms of Cross-linking and on the Final Structure of the Resins." Polymers and Polymer Composites 11, no. 4 (May 2003): 233–62. http://dx.doi.org/10.1177/096739110301100401.
Abstract:
The physicochemical characterization of the structures of the oligomers (n < 4) in resols has been carried out by fragmenting monomers in LC/UV/MS and LC/UV/MS/MS. Fragmentation mechanisms are related to the numbers and positions of substituents on the aromatic ring and to the types of oligomer junctions. It was more difficult to determine the structures of phenol hemiacetals and dimer hemiacetals because of the large number of position isomers. The resols were prepared with differing molar ratios R = Formaldehyde/Phenol and catalysts. They were cross-linked using two industrially recommended heat cycles. The progression of resin cross-linking was determined by solid state 13C NMR (CP/MAS). The residual percentage of monomers and oligomers at n < 4 was determined in leachates (water and methanol) and characterized by LC/UV/MS. The results for cross-linking advancement were correlated with the various synthesis parameters (ratio R, type of catalyst and heat cycle).
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Feith, André, Attila Teleki, Michaela Graf, Lorenzo Favilli, and Ralf Takors. "HILIC-Enabled 13C Metabolomics Strategies: Comparing Quantitative Precision and Spectral Accuracy of QTOF High- and QQQ Low-Resolution Mass Spectrometry." Metabolites 9, no. 4 (April 2, 2019): 63. http://dx.doi.org/10.3390/metabo9040063.
Abstract:
Dynamic 13C-tracer-based flux analyses of in vivo reaction networks still require a continuous development of advanced quantification methods applying state-of-the-art mass spectrometry platforms. Utilizing alkaline HILIC chromatography, we adapt strategies for a systematic quantification study in non- and 13C-labeled multicomponent endogenous Corynebacterium glutamicum extracts by LC-QTOF high resolution (HRMS) and LC-QQQ tandem mass spectrometry (MS/MS). Without prior derivatization, a representative cross-section of 17 central carbon and anabolic key intermediates were analyzed with high selectivity and sensitivity under optimized ESI-MS settings. In column detection limits for the absolute quantification range were between 6.8–304.7 (QQQ) and 28.7–881.5 fmol (QTOF) with comparable linearities (3–5 orders of magnitude) and enhanced precision using QQQ-MRM detection. Tailor-made preparations of uniformly (U)13C-labeled cultivation extracts for isotope dilution mass spectrometry enabled the accurate quantification in complex sample matrices and extended linearities without effect on method parameters. Furthermore, evaluation of metabolite-specific m+1-to-m+0 ratios (ISR1:0) in non-labeled extracts exhibited sufficient methodical spectral accuracies with mean deviations of 3.89 ± 3.54% (QTOF) and 4.01 ± 3.01% (QQQ). Based on the excellent HILIC performance, conformity analysis of time-resolved isotopic enrichments in 13C-tracer experiments revealed sufficient spectral accuracy for QQQ-SIM detection. However, only QTOF-HRMS ensures determination of the full isotopologue space in complex matrices without mass interferences.
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Lee, Youngsun, Jung Hee Kim, Da-Jung You, Cho-Il Kim, Jee-Yeon Lee, and Hyun-Mee Park. "Analytical Method of Multi-Mycotoxins in Table-Ready Foods for a Total Diet Study Using Stable Isotope Dilution Liquid Chromatography–Tandem Mass Spectrometry." Journal of AOAC International 102, no. 6 (November 1, 2019): 1657–65. http://dx.doi.org/10.5740/jaoacint.19-0031.
Abstract:
Background: Determining the multi-mycotoxins present in table-ready foods is necessary for a total diet study. However, so far, most methods of analyzing multi-mycotoxins apply to raw foods. Therefore, a reliable method for analyzing multi-mycotoxins in table-ready foods is needed. Objective: We developed and validated methods of multi-mycotoxin analysis that employed stable isotope dilution with LC–tandem MS (LC–MS/MS) using two representative matrices. Methods: Samples were fortified with [13C]-labeled mycotoxins as internal standards and extracted with 50% acetonitrile in water for high-carbohydrate foods and 3% formic acid in acetonitrile for high-protein and/or high-fat foods, cleaned up with n-hexane and the quick, easy, cheap, effective, rugged, and safe (QuEChERS) method, and followed up by LC–MS/MS. Results: Validation of the methods was performed, and the results were as follows: the correlation coefficient, R2, was 0.99; method detection limit, 0.01–2.4 μg/kg; recoveries, 83.6–114%; precision, 0.8–10 (intraday) and 3.1–22% (interday); interlaboratory reproducibility, ≤15%; and uncertainty, 3.5–19%error. The applicability of the methods was evaluated by analyzing table-ready foods spiked with standards. Conclusions: These methods were successfully evaluated and deemed appropriate for determining the multi-mycotoxins in table-ready foods. Highlights: This work demonstrates that stable isotope dilution with LC–MS/MS can be effectively used to analyze multi-mycotoxins simultaneously in a total diet study.
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Lee, Youngsun, Jung Hee Kim, Da-Jung You, Cho-Il Kim, Jee-Yeon Lee, and Hyun-Mee Park. "Analytical Method of Multi-Mycotoxins in Table-Ready Foods for a Total Diet Study Using Stable Isotope Dilution Liquid Chromatography–Tandem Mass Spectrometry." Journal of AOAC INTERNATIONAL 102, no. 6 (November 1, 2019): 1657–65. http://dx.doi.org/10.1093/jaoac/102.6.1657.
Abstract:
Abstract Background: Determining the multi-mycotoxins present in table-ready foods is necessary for a total diet study. However, so far, most methods of analyzing multi-mycotoxins apply to raw foods. Therefore, a reliable method for analyzing multi-mycotoxins in table-ready foods is needed. Objective: We developed and validated methods of multi-mycotoxin analysis that employed stable isotope dilution with LC–tandem MS (LC–MS/MS) using two representative matrices. Methods: Samples were fortified with [13C]-labeled mycotoxins as internal standards and extracted with 50% acetonitrile in water for high-carbohydrate foods and 3% formic acid in acetonitrile for high-protein and/or high-fat foods, cleaned up with n-hexane and the quick, easy, cheap, effective, rugged, and safe (QuEChERS) method, and followed up by LC–MS/MS. Results: Validation of the methods was performed, and the results were as follows: the correlation coefficient, R2, was 0.99; method detection limit, 0.01–2.4 μg/kg; recoveries, 83.6–114%; precision, 0.8–10 (intraday) and 3.1–22% (interday); interlaboratory reproducibility, ≤15%; and uncertainty, 3.5–19%error. The applicability of the methods was evaluated by analyzing table-ready foods spiked with standards. Conclusions: These methods were successfully evaluated and deemed appropriate for determining the multi-mycotoxins in table-ready foods. Highlights: This work demonstrates that stable isotope dilution with LC–MS/MS can be effectively used to analyze multi-mycotoxins simultaneously in a total diet study.
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Rühl, Martin, Beat Rupp, Katharina Nöh, Wolfgang Wiechert, Uwe Sauer, and Nicola Zamboni. "Collisional fragmentation of central carbon metabolites in LC-MS/MS increases precision of 13C metabolic flux analysis." Biotechnology and Bioengineering 109, no. 3 (October 28, 2011): 763–71. http://dx.doi.org/10.1002/bit.24344.
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Hoffman, Melissa A., Michael Schmeling, Jayme L. Dahlin, Nicholas J. Bevins, Donald P. Cooper, Petr Jarolim, Robert L. Fitzgerald, and Andrew N. Hoofnagle. "Calibrating from Within: Multipoint Internal Calibration of a Quantitative Mass Spectrometric Assay of Serum Methotrexate." Clinical Chemistry 66, no. 3 (February 13, 2020): 474–82. http://dx.doi.org/10.1093/clinchem/hvaa003.
Abstract:
Abstract Background Clinical LC-MS/MS assays traditionally require that samples be run in batches with calibration curves in each batch. This approach is inefficient and presents a barrier to random access analysis. We developed an alternative approach called multipoint internal calibration (MPIC) that eliminated the need for batch-mode analysis. Methods The new approach used 4 variants of 13C-labeled methotrexate (0.026–10.3 µM) as an internal calibration curve within each sample. One site carried out a comprehensive validation, which included an evaluation of interferences and matrix effects, lower limit of quantification (LLOQ), and 20-day precision. Three sites evaluated assay precision and linearity. MPIC was also compared with traditional LC-MS/MS and an immunoassay. Results Recovery of spiked analyte was 93%–102%. The LLOQ was validated to be 0.017 µM. Total variability, determined in a 20-day experiment, was 11.5%CV. In a 5-day variability study performed at each site, total imprecision was 3.4 to 16.8%CV. Linearity was validated throughout the calibrator range (r2 > 0.995, slopes = 0.996–1.01). In comparing 40 samples run in each laboratory, the median interlaboratory imprecision was 6.55%CV. MPIC quantification was comparable to both traditional LC-MS/MS and immunoassay (r2 = 0.96–0.98, slopes = 1.04–1.06). Bland-Altman analysis of all comparisons showed biases rarely exceeding 20% when MTX concentrations were >0.4 µM. Conclusion The MPIC method for serum methotrexate quantification was validated in a multisite proof-of-concept study and represents a big step toward random-access LC-MS/MS analysis, which could change the paradigm of mass spectrometry in the clinical laboratory.
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Veršilovskis, A., J. Geys, B. Huybrechts, E. Goossens, S. De Saeger, and A. Callebaut. "Simultaneous determination of masked forms of deoxynivalenol and zearalenone after oral dosing in rats by LC-MS/MS." World Mycotoxin Journal 5, no. 3 (August 1, 2012): 303–18. http://dx.doi.org/10.3920/wmj2012.1411.
Abstract:
In vivo metabolism of masked or conjugated mycotoxins is poorly documented as standards are not commercially available and indirect analysis using hydrolytic enzymes is difficult to validate and cumbersome. We synthesised zearalenone-14-glucoside (ZEA-14G) chemically. Deoxynivalenol-3-glucuronide (DON-3GlcA) and glucuronides of 3- and 15-acetyl-deoxynivalenol (3- and 15-ADON-GlcAs), de-epoxydeoxynivalenol, zearalenone (ZEA), α- and β-zearalenol (α- and β-ZOL) were synthesised using rat microsomes. For the first time three ADON-GlcAs were synthesised: two 3-ADON-GlcAs and one 15-ADON-GlcA. After purification, the masked mycotoxin and the metabolites were characterised by NMR (DON-3GlcA, ZEA-14G) or by full scan MS, MS/MS fragmentation, UV-spectra, β-glucosidase and β-glucuronidase treatment. In a first experiment, rats were fed orally DON-3-glucoside (DON-3G) and ZEA-14G, together with 13C-DON and 13C-ZEA and were sacrificed after 55 minutes. A total of 21 masked metabolites, metabolites and parent mycotoxins were quantified in rat organs. Whereas DON-3G was hardly hydrolysed in the stomach, ZEA was clearly formed from ZEA-14G. In a second experiment, 3- and 15-ADON were given orally to rats. The acetylated forms of DON were hydrolysed in the stomach, in contrast to DON-3G. Rats can directly glucuronidate ADONs without deacetylation. Neither DOM, α- or β-ZOL nor their glucuronides could be quantified. Glucuronidated 3-ADON accumulated in the small intestines, together with DON-3GlcA in rats fed orally with 3- and 15-ADON. These differences in masked mycotoxins metabolism can be important in risk analysis of masked mycotoxins in food and feed.
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Wojcińska, Małgorzata, Jeffrey Williams, Tom J. Mabry, Ahmed A. Ahmed, Barry D. Davis, Gabor Tóth, Nabil H. El-Sayed, Irena Matławska, and Jennifer Clevinger. "Flavonol Triglycosides from the Leaves of Silphium Albiflorum." Natural Product Communications 1, no. 11 (November 2006): 1934578X0600101. http://dx.doi.org/10.1177/1934578x0600101105.
Abstract:
In the course of chemotaxonomic studies of the genus Silphium two new and six known flavonol glycosides were isolated from the leaves of S. albiflorum. The structures of the new flavonoids were established by spectral analysis (1H NMR, 13C NMR, HMQC, HMBC, ROESY, TOCSY, MS) as isorhamnetin 3-O-α-L-rhamnosyl (1′“→6″)-O-β-D-galactopyranoside 7-O-β-D-apiofuranoside (1) and quercetin 3-O-α-L-rhamnosyl (1′“→6″)-O-β-D-galactopyranoside 7-O-β-D-apiofuranoside (2). LC-MS and LC-MSn (with post-column manganese complexation) were applied to elucidate the structures of some of the studied compounds.
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LeBlanc, Patricia, Nadine Merkley, Krista Thomas, Nancy I. Lewis, Khalida Békri, Susan LeBlanc Renaud, Frances R. Pick, Pearse McCarron, Christopher O. Miles, and Michael A. Quilliam. "Isolation and Characterization of [D-Leu1]microcystin-LY from Microcystis aeruginosa CPCC-464." Toxins 12, no. 2 (January 23, 2020): 77. http://dx.doi.org/10.3390/toxins12020077.
Abstract:
[D-Leu1]MC-LY (1) ([M + H]+ m/z 1044.5673, Δ 2.0 ppm), a new microcystin, was isolated from Microcystis aeruginosa strain CPCC-464. The compound was characterized by 1H and 13C NMR spectroscopy, liquid chromatography–high resolution tandem mass spectrometry (LC–HRMS/MS) and UV spectroscopy. A calibration reference material was produced after quantitation by 1H NMR spectroscopy and LC with chemiluminescence nitrogen detection. The potency of 1 in a protein phosphatase 2A inhibition assay was essentially the same as for MC-LR (2). Related microcystins, [D-Leu1]MC-LR (3) ([M + H]+ m/z 1037.6041, Δ 1.0 ppm), [D-Leu1]MC-M(O)R (6) ([M + H]+ m/z 1071.5565, Δ 2.0 ppm) and [D-Leu1]MC-MR (7) ([M + H]+ m/z 1055.5617, Δ 2.2 ppm), were also identified in culture extracts, along with traces of [D-Leu1]MC-M(O2)R (8) ([M + H]+ m/z 1087.5510, Δ 1.6 ppm), by a combination of chemical derivatization and LC–HRMS/MS experiments. The relative abundances of 1, 3, 6, 7 and 8 in a freshly extracted culture in the positive ionization mode LC–HRMS were ca. 84, 100, 3.0, 11 and 0.05, respectively. These and other results indicate that [D-Leu1]-containing MCs may be more common in cyanobacterial blooms than is generally appreciated but are easily overlooked with standard targeted LC–MS/MS screening methods.
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Pfeiffer, Christine M., Zia Fazili, Les McCoy, Ming Zhang, and Elaine W. Gunter. "Determination of Folate Vitamers in Human Serum by Stable-Isotope-Dilution Tandem Mass Spectrometry and Comparison with Radioassay and Microbiologic Assay." Clinical Chemistry 50, no. 2 (February 1, 2004): 423–32. http://dx.doi.org/10.1373/clinchem.2003.026955.
Abstract:
Abstract Background: Current clinical methods for folate give different results and cannot measure the various forms of folate. We developed an isotope-dilution tandem mass spectrometric method coupled to liquid chromatography (LC/MS/MS) as a candidate reference method for 5-methyltetrahydrofolic acid (5MeTHF), 5-formyltetrahydrofolic acid (5FoTHF), and folic acid (FA) in human serum. Methods: We quantitatively isolated folates from 275 μL of serum with a phenyl solid-phase extraction cartridge, then detected and quantified them in stabilized serum extracts by positive-ion electrospray ionization LC/MS/MS. We used an isocratic mobile phase of acetic acid in organic solvent on a C8 analytical column. 13C-labeled folates were used as internal standards. Results: Limits of detection in serum were 0.13 (5MeTHF), 0.05 (5FoTHF), and 0.07 (FA) nmol/L. Within- and between-run imprecision (CV) was <7% for 5MeTHF and <10% for 5FoTHF at concentrations >0.5 nmol/L, and <10% for FA at concentrations >2.0 nmol/L. Total folate (TFOL) concentrations determined by competitive protein binding radioassay were ∼9% lower than results obtained with LC/MS/MS. The microbiologic assay gave ∼15% higher TFOL results with FA calibrator and no difference with 5MeTHF calibrator. The mean (SD) [range] TFOL in 42 sera was 35.5 (17.8) [6.5–75.6] nmol/L. Thirty-two samples with TFOL <50 nmol/L had, on average, 93.3% 5MeTHF, 2.3% FA, and 4.4% 5FoTHF. Ten samples with TFOL >50 nmol/L had, on average, 81.7% 5MeTHF, 15.7% FA, and 2.5% 5FoTHF. Conclusions: This stable-isotope-dilution LC/MS/MS method can quantify 5MeTHF, 5FoTHF, and FA in serum. Currently used clinical assays agree with this candidate reference method.
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Bouajila, J., G. Raffin, H. Waton, C. Sanglar, J. O. Païsse, and M. F. Grenier-Loustalot. "Phenolic Resins – Characterizations and Kinetic Studies of Different Resols Prepared with Different Catalysts and Formaldehyde/Phenol Ratios (I)." Polymers and Polymer Composites 10, no. 5 (July 2002): 341–60. http://dx.doi.org/10.1177/096739110201000502.
Abstract:
The physicochemical and kinetic properties of resols prepared with different catalysts (NaOH, LiOH and Ba(OH)2) and variable formaldehyde/phenol ratios (2.5 £ R £ 3.5) were followed to determine their effects on the mechanisms and reaction products at a fixed pH and temperature. Kinetic monitoring and quantification of residual monomers were carried out by liquid chromatography coupled with mass spectrometry (LC/UV/MS), by 13C nuclear magnetic resonance (NMR) and by chemical assay for formaldehyde. Oligomer formation (n ≥ 2) was determined by LC/UV/MS, size exclusion chromatography (SEC) and 13C NMR. It was found that minor compounds form during syntheses (phenol methanol hemiacetals, hemiacetals of phenol and of oligomers…) and that the ratio R affects primarily the kinetics of formation of monomers and oligomers, in contrast to the catalysts that modify reaction mechanisms. The understanding of the structure of the resols was an important step for the determination of the final properties of the material.
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Solfrizzo, Michele, Lucia Gambacorta, Rita Bibi, Martina Ciriaci, Angela Paoloni, and Ivan Pecorelli. "Multimycotoxin Analysis by LC-MS/MS in Cereal Food and Feed: Comparison of Different Approaches for Extraction, Purification, and Calibration." Journal of AOAC INTERNATIONAL 101, no. 3 (May 1, 2018): 647–57. http://dx.doi.org/10.5740/jaoacint.17-0339.
Abstract:
Abstract Twelve different approaches commonly used for the simultaneous LC tandem MS (MS/MS) determination of mycotoxins (deoxynivalenol, aflatoxins, ochratoxin A, T-2 and HT-2 toxins, fumonisins, and zearalenone) were tested in cereals and feed materials. They comprised different extraction solvents, types of cleanup [solid-phase extraction, QuEChERS, and immunoaffinity (IMA)], and calibration approaches (external or matrix-matched). The percentage of mycotoxins with acceptable recovery, according to Regulation (EC) No. 401/2006, ranged from 9 to 100%. The approach giving the highest percentage of acceptable results was selected and further tested for corn, rice, and feed spiked at three different mycotoxin levels (low, medium, and high). The method is based on extraction with MeOH–water (70 + 30, v/v) and cleanup with two multiantibody IMA columns. For corn and rice spiked at low mycotoxin levels, a significant matrix effect was observed and was compensated by using 13C calibration. At higher mycotoxin levels (medium and high), matrix effects were negligible as no significant differences were observed for the majority of recovery results calculated by 13C calibration and external calibration. Although the proposed method still needs improvement in terms of accuracy and, to a lesser extent, precision, it was successfully tested with four proficiency tests in buckwheat, corn, rice, and feed, giving acceptable z-scores for 97% (34 out of 35) of results.
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Kumar, Rakesh, and Gursharan Singh. "Reactions of MoCl5 with 4-Methylpyridine, 2-Methylpyridine and 1-Methylimidazole in Tetrahydrofuran." Oriental Journal Of Chemistry 37, no. 5 (October 30, 2021): 1178–86. http://dx.doi.org/10.13005/ojc/370523.
Abstract:
MoCl5 reactions with 4-methylpyridine/2-methylpyridine/1-methylimidazole in THF in 1:1/1:2 stoichiometric ratios, at room temperature were carried out. The following products were synthesized: MoO2Cl(C6H7N), 1;Mo2O2Cl5(C6H7N)2(C4H8O)2,2; Mo4O4Cl4(C6H7N)3(C4H8O)2, 3 and Mo2O4Cl4(C4H6N)2(C4H8O), 4. These compounds have been investigated by FT-IR (transmission mode), FT-1H NMR, FT -13C NMR, microbiological, LC-MS and elemental (C, H, N, Mo, Cl) studies. In view of the sensitivity of all the reactants and products towards oxidation/hydrolysis by air/moisture, all the reactions and products were handled using dry nitrogen atmosphere in vacuum line. LC-MS and elemental studies agree with the formulae of compounds.
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Zille, Andrea, Barbara Górnacka, Astrid Rehorek, and Artur Cavaco-Paulo. "Degradation of Azo Dyes by Trametes villosa Laccase over Long Periods of Oxidative Conditions." Applied and Environmental Microbiology 71, no. 11 (November 2005): 6711–18. http://dx.doi.org/10.1128/aem.71.11.6711-6718.2005.
Abstract:
ABSTRACT Trametes villosa laccase was used for direct azo dye degradation, and the reaction products that accumulated after 72 h of incubation were analyzed. Liquid chromatography-mass spectrometry (LC-MS) analysis showed the formation of phenolic compounds during the dye oxidation process as well as a large amount of polymerized products that retain azo group integrity. The amino-phenol reactions were also investigated by 13C-nuclear magnetic resonance and LC-MS analysis, and the polymerization character of laccase was shown. This study highlights the fact that laccases polymerize the reaction products obtained during long-term batch decolorization processes with azo dyes. These polymerized products provide unacceptable color levels in effluents, limiting the application of laccases as bioremediation agents.
40
Shupeniuk, Vasyl, Tetyana Taras, Oksana Sabadakh, Eugene Luchkevich, and Yurii Kornii. "Synthesis some 4-substituted 9,10-anthraquinones." French-Ukrainian Journal of Chemistry 8, no. 1 (2020): 58–65. http://dx.doi.org/10.17721/fujcv8i1p58-65.
Abstract:
New 4-substituted 9,10-anthraquinones (6 compouds) with amino derivations fragments were synthesized through the substitution of the bromaminic acid by amines using the Ullmann coupling reaction. The structures of the synthesized compounds were determined using LC-MS, 1H NMR, 13C NMR spectroscopy, and elemental analysis data.
41
Krska, Rudolf, Elvira Welzig, Ralf D. Josephs, Wolfgang Kandler, Hans Pettersson, Susan MacDonald, Adrian Charlton, et al. "Purity Assessment of Crystalline Zearalenone." Journal of AOAC INTERNATIONAL 86, no. 4 (July 1, 2003): 722–28. http://dx.doi.org/10.1093/jaoac/86.4.722.
Abstract:
Abstract Commercially available solid zearalenone (ZON) to be used as a certified liquid calibrant (BCR-699) in a project funded by the European Commission within the Standard Measurement and Testing program was characterized and its purity determined. The degree of purity of the ZON was examined by UV spectrophotometer, liquid chromatography (LC) with diode array and fluorescence detection, 1H and 13C-NMR spectrometry, LC–mass spectrometry (LC/MS/MS), ion chromatography (IC), and differential scanning calorimetry (DSC). The diagrams obtained from DSC analysis and the UV spectrum showed no detectable impurities. Likewise, no impurities were observed by LC analysis with both diode array and fluorescence detection. IC determination revealed negligible contamination of ZON with chloride of 0.020 ± 0.005% and nitrate of 0.016 ± 0.006%. Zearalanone (ZAN) was identified as one of 2 minor (0.2%) impurities by LC/MS/MS. The 1H-NMR measurements revealed an additional peak, which has not been previously reported in the literature. It could be identified as part of the ZON spectrum as the signal arising from the phenolic proton attached to C4'. The manufacturer states an additional contamination with 0.2% methylene chloride, which could be confirmed to an extent of 0.1% by 1H-NMR. Minor impurities, whose structures remain unknown, were discovered at 3.5 and <1 ppm. Total percentage of impurities based on NMR measurement was estimated not to exceed 1%. A purity of 99.5% with a tolerance of ±0.5% was finally attributed to the ZON studied in this project.
42
Regiani, Anelise M., Agnieszka Pawlicka, A. Aprigio S. Curvelo, Alessandro Gandini, and Jean-François Le Nest. "Hidroxietil celulose enxertada com poliéteres." Polímeros 9, no. 3 (September 1999): 45–50. http://dx.doi.org/10.1590/s0104-14281999000300009.
Abstract:
Foram preparadas amostras de hidroxietil celulose (HEC) enxertada com poliéteres para aplicação como eletrólitos sólidos poliméricos. Amostras comerciais de HEC foram caracterizadas por ¹H e 13C RMN, FTIR e viscosimetria, visando a determinação dos respectivos graus de substituição molar (MS), grau de substituição (DS) e grau de polimerização (DP). Amostras comerciais de diaminas de poli(óxido de etileno) (POE) e poli(óxido de propileno) (POP) foram também caracterizadas antes de serem convertidas nos correspondentes diisocianatos. As redes foram obtidas através de reações de condensação das HEC com os diisocianatos e caracterizadas por FTIR, UV-Vis, difração de raios-X e análises térmicas, a fim de definir suas Tg.
43
Krska, Rudolf, Elisabeth Szente, Martin Freudenschuss, Christian Hametner, and Peter Zöllner. "Purity Assessment of Commercially Available Crystalline Deoxynivalenol." Journal of AOAC INTERNATIONAL 87, no. 4 (July 1, 2004): 909–19. http://dx.doi.org/10.1093/jaoac/87.4.909.
Abstract:
Abstract Deoxynivalenol (DON) obtained from 2 commercial sources was characterized, and its purity was determined. The structural identity of DON was confirmed by 1 Hand 13C-nuclear magnetic resonance (NMR) spectroscopy, gas chromatography with mass spectrometric (GC/MS) detection, and infrared/attenuated total reflectance (IR/ATR) spectroscopy. NMR spectra showed shifts that varied from previously published data. However, we established a complete, unambiguous assignment for all signals. Chromatograms obtained by GC/MS were almost identical for both investigated samples and confirmed the structure of DON. Likewise, IR/ATR spectra verified the identity of DON. The degree of purity was determined by liquid chromatography (LC) with a variable wavelength detector, LC/MS/MS, GC with electron-capture detection (GC-ECD), and ultraviolet (UV) spectrophotometry. The purity check using LC showed a single peak in both chromatograms. With LC/MS/MS measurements, we could detect small amounts of impurities in the crystalline DON from both sources. In data obtained by GC-ECD, no differences in purity were observed. The UV measurements showed an absorption maximum at 217 nm. The mean εm of the extinction coefficients was calculated as 6727 (L/cm/mol) for DON (Sigma) and 6825 (L/cm/mol) for DON (Biopure). Finally, the purity of DON from the 2 commercial sources was calculated as >96 and >98%, respectively. Although the DON produced by both providers can be considered sufficiently pure for routine analysis of trichothecenes in food and feed, this work again demonstrated that the impurity of the solid mycotoxin constitutes the greatest contribution to the overall uncertainty of a mycotoxin calibrant.
44
Khaniani, Yeganeh, Matthias Lipfert, Dipanjan Bhattacharyya, Rolando Perez Pineiro, Jiamin Zheng, and David Wishart. "A Simple and Convenient Synthesis of Unlabeled and 13C-Labeled 3-(3-Hydroxyphenyl)-3-Hydroxypropionic Acid and Its Quantification in Human Urine Samples." Metabolites 8, no. 4 (November 21, 2018): 80. http://dx.doi.org/10.3390/metabo8040080.
Abstract:
An improved method to synthesize the highly abundant and biomedically important urinary metabolite 3-(3-hydroxyphenyl)-3-hydroxypropionic acid (HPHPA) is reported. The modified protocol is based on an indium-mediated sonochemical Reformatsky reaction. The synthesis is a simple two-step route as opposed to a complex four-step route previously reported in the literature that requires specialized equipment, flammable materials, and high-pressure reaction vessels. The described procedure also provides an expedient route to prepare a 13C isotopically labeled HPHPA that can be used as a standard for quantitative LC-MS analysis. This report also illustrates how the synthesized metabolite standard was used to detect and accurately quantify its presence in human urine samples using both NMR and LC-MS techniques.
45
Trivedi, Mahendra Kumar, Alice Branton, Dahryn Trivedi, and Snehasis Jana. "Structural Characterization and Isotopic Abundance Ratio Analysis of the Consciousness Energy Healing Treated Ofloxacin." Journal of Current Scientific Research 1, no. 3 (April 27, 2021): 11–20. http://dx.doi.org/10.14302/issn.2766-8681.jcsr-21-3770.
Abstract:
Ofloxacin is an antibiotic, useful against the number of bacterial infections. This scientific investigation was performed to identify the impact of the Trivedi Effect®-Consciousness Energy Healing Treatment on the structural properties and the isotopic abundance ratio of ofloxacin using sophisticated analytical techniques. Ofloxacin sample was divided into control and treated parts. Only the treated ofloxacin received the Consciousness Energy Healing Treatment remotely by a well-known Biofield Energy Healer, Mr. Mahendra Kumar Trivedi. The LC-MS spectra of both the samples of ofloxacin at retention time 3 minutes exhibited the mass of the protonated molecular ion peak at m/z 362.17 (M+H)+. The chromatographic peak area% of the treated ofloxacin (52.4%) was increased by 2.03% compared to the control sample (51.36%). The LC-MS based isotopic abundance ratio of PM+1/PM in the Biofield Treated ofloxacin was significantly increased by 22.43% compared with the control sample. Similarly, the GC-MS based isotopic abundance ratio of PM+1/PM in the Biofield Treated ofloxacin was significantly increased by 19.24% compared with the control sample. The LC-MS and GC-MS based isotopic abundance ratio of PM+1/PM (2H/1H or 15N/14N or 13C/12C or 17O/16O) was significantly increased in the Biofield Treated ofloxacin as compared to the control sample. Thus,2H, 15N, 13C, and17O contributions from (C18H21FN3O4)+ to m/z 363.17 in the treated ofloxacin were significantly increased compared with the control sample. The increased isotopic abundance ratio of the Trivedi Effect®-Consciousness Energy Healing Treated ofloxacin may increase the intra-atomic bond strength and increase its physical stability. The new form of treated ofloxacin would be more stable, better soluble, and bioavailable compared to the control sample. It would be more useful to design efficacious pharmaceutical formulations that might offer better therapeutic response against infections in the urethra, urinary tract, gonorrhoea, pneumonia, infectious diarrhoea, bronchitis, cellulitis, bacterial infection of the eye and ear, multidrug-resistant tuberculosis, prostatitis, otitis media, plague, etc.
46
Schlösser, Joachim, Armin Mehlich, Frank Ballwanz, and M. Petz. "Preparation of doubly 13C-labelled benzylpenicillin as internal standard for residue analytical use with GC/MS and LC/MS." Fresenius' Journal of Analytical Chemistry 360, no. 3-4 (February 1998): 498–501. http://dx.doi.org/10.1007/s002160050748.
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Zhang, Kai, Steven Tan, and David Xu. "Determination of Mycotoxins in Dried Fruits Using LC-MS/MS—A Sample Homogeneity, Troubleshooting and Confirmation of Identity Study." Foods 11, no. 6 (March 21, 2022): 894. http://dx.doi.org/10.3390/foods11060894.
Abstract:
To monitor co-exposure to toxic mycotoxins in dried fruits, it is advantageous to simultaneously determine multiple mycotoxins using a single extraction and liquid chromatography with tandem mass spectrometry (LC-MS/MS) analysis. In this study, we applied a stable isotope dilution and LC-MS/MS method to multi-mycotoxin analysis in dried fruits, selecting raisins, plums, figs, and cranberries for matrix extension. Samples were prepared using cryogenic grinding, followed by the fortification of carbon-13 (13C) uniformly labeled internal standards for twelve mycotoxins, and extraction using 50% acetonitrile. Homogeneity of prepared samples, defined as particle size Dv90 < 850 µm for the tested matrices, was characterized using a laser diffraction particle size analyzer, and reached using cryogenic grinding procedures. The majority of recoveries in the four matrices for aflatoxins and ochratoxin A spiked at 1–100 ng/g; fumonisins, T-2 toxin, HT-2 toxin, and zearalenone spiked at 10–1000 ng/g, ranged from 80 to 120% with relative standard deviations (RSDs) of <20%. Deoxynivalenol was not detected at 10 and 100 ng/g in plums, and additional troubleshooting procedures using liquid-liquid extraction (LLE), solid phase extraction (SPE), and elution gradient were evaluated to improve the detectability of the mycotoxin. Furthermore, we confirmed the identity of detected mycotoxins, ochratoxin A and deoxynivalenol, in incurred samples using enhanced product ion scans and spectral library matching.
48
Fujiwara, Tao, Ayumi Uehara, Junichi Kitajima, Tsukasa Iwashina, Sadamu Matsumoto, and Yasuyuki Watano. "Genkwanin 4′-O-glucosyl-(1→2)-rhamnoside from New Chemotype of Asplenium normale in Japan." Natural Product Communications 9, no. 9 (September 2014): 1934578X1400900. http://dx.doi.org/10.1177/1934578x1400900917.
Abstract:
New flavone glycoside, genkwanin 4′- O-β-glucopyranosyl-(1→2)- O-α-rhamnopyranoside was isolated from the fronds of new chemotype of Asplenium normale D.Don, together with two known C-glycosylflavones, vicenin-2 and lucenin-2. The chemical structure of the isolated glycoside was established by UV, LC-MS, characterization of acid hydrolysates, and 1H and 13C NMR spectroscopy.
49
Dai, Charles, Yoon-Mi Chung, Eric A. Klein, and Nima Sharifi. "A dual stable isotope method by LC-MS/MS to define patterns of androgen metabolism in localized versus advanced prostate cancer." Journal of Clinical Oncology 34, no. 2_suppl (January 10, 2016): 40. http://dx.doi.org/10.1200/jco.2016.34.2_suppl.40.
Abstract:
40 Background: Prior work has shown that androstenedione (AD) rather than testosterone (T) is the preferred substrate of 5α-reductase for dihydrotestosterone (DHT) synthesis in castration-resistant prostate cancer. However, patterns of metabolism in hormone-naive prostate cancer are still poorly defined. Previously, we reported on the utility of dual radioisotope labeling of steroid precursors to characterize androgen metabolism in localized prostate tissue. We now describe an alternative approach via stable isotope labeling and analysis by liquid chromatography-tandem mass spectrometry (LC-MS/MS), which has unique advantages over the former method. Methods: LNCaP cell lines and prostate tissue from patients undergoing radical prostatectomy for localized cancer were incubated in serum-free media, spiked with 13C-labeled AD and 2H-labeled T. Media was collected at 7, 24, and 48 hours of incubation. Steroids were extracted, separated, and then analyzed by way of LC-MS/MS to identify labeled metabolites of AD and T. Results: Incubation of labeled AD and T resulted in conversion over time to both 13C-labeled and 2H-labeled downstream metabolites, 5α-dione and DHT. Although both precursors contributed to 5α-dione and DHT formation, the steroid of origin could be determined on the basis of differential labeling. In ex-vivo tissue incubations, unlabeled 5α-dione was also observed, which was distinguishable from its stable isotopic form and most likely represents endogenous steroid. Conclusions: Both cell lines and tissue appear to metabolize labeled AD and T, and formation of DHT occurs through both precursors. Furthermore, the presence of endogenous 5α-dione suggests that alternative pathways of DHT synthesis, which bypass T, may be naturally accessible in the hormone-naïve setting. We propose a robust ex-vivo technique to readily track simultaneous pathways of DHT synthesis in prostate cancer. Future work will focus on defining metabolic phenotypes of localized prostate cancer and specific patterns of flux under different hormonal and pharmacologic conditions.
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Zhang, Kai, and Lauren Zhang. "Determination of Patulin in Apple Juice and Apple-Derived Products Using a Robotic Sample Preparation System and LC-APCI-MS/MS." Toxins 16, no. 6 (May 23, 2024): 238. http://dx.doi.org/10.3390/toxins16060238.
Abstract:
Patulin, a toxic mycotoxin, can contaminate apple-derived products. The FDA has established an action level of 50 ppb (ng/g) for patulin in apple juice and apple juice products. To effectively monitor this mycotoxin, there is a need for adequate analytical methods that can reliably and efficiently determine patulin levels. In this work, we developed an automated sample preparation workflow followed by liquid chromatography–atmospheric pressure chemical ionization tandem mass spectrometry (LC-APCI-MS/MS) detection to identify and quantify patulin in a single method, further expanding testing capabilities for monitoring patulin in foods compared to traditional optical methods. Using a robotic sample preparation system, apple juice, apple cider, apple puree, apple-based baby food, applesauce, fruit rolls, and fruit jam were fortified with 13C-patulin and extracted using dichloromethane (DCM) without human intervention, followed by an LC-APCI-MS/MS analysis in negative ionization mode. The method achieved a limit of quantification of 4.0 ng/g and linearity ranging from 2 to 1000 ng/mL (r2 > 0.99). Quantitation was performed with isotope dilution using 13C-patulin as an internal standard and solvent calibration standards. Average recoveries (relative standard deviations, RSD%) in seven spike matrices were 95% (9%) at 10 ng/g, 110% (5%) at 50 ng/g, 101% (7%) at 200 ng/g, and 104% (4%) at 1000 ng/g (n = 28). The ranges of within-matrix and between-matrix variability (RSD) were 3–8% and 4–9%, respectively. In incurred samples, the identity of patulin was further confirmed with a comparison of the information-dependent acquisition-enhanced product ion (IDA-EPI) MS/MS spectra to a reference standard. The metrological traceability of the patulin measurements in an incurred apple cider (21.1 ± 8.0 µg/g) and apple juice concentrate (56.6 ± 15.6 µg/g) was established using a certified reference material and calibration data to demonstrate data confidence intervals (k = 2, 95% confidence interval).