Journal articles: 'Chromatographic assays'

1

Ristuccia, Patricia A. "Liquid Chromatographic Assays of Antimicrobial Agents." Journal of Liquid Chromatography 10, no. 2-3 (February 1987): 241–76. http://dx.doi.org/10.1080/01483918708066718.

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Reif, Van D., Kevin L. Kaufmann, Nicholas J. Deangelis, and Mary C. Frankhouser. "Liquid Chromatographic Assays for Barbiturate Injections." Journal of Pharmaceutical Sciences 75, no. 7 (July 1986): 714–16. http://dx.doi.org/10.1002/jps.2600750721.

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Zhao, Qiang, Xing-Fang Li, Yuanhua Shao, and X. Chris Le. "Aptamer-Based Affinity Chromatographic Assays for Thrombin." Analytical Chemistry 80, no. 19 (October 2008): 7586–93. http://dx.doi.org/10.1021/ac801206s.

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Turpeinen, U., P. Lehtovirta, H. Alfthan, and U. H. Stenman. "Interference by human anti-mouse antibodies in CA 125 assay after immunoscintigraphy: anti-idiotypic antibodies not neutralized by mouse IgG but removed by chromatography." Clinical Chemistry 36, no. 7 (July 1, 1990): 1333–38. http://dx.doi.org/10.1093/clinchem/36.7.1333.

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Abstract Falsely increased concentrations of the ovarian carcinoma-associated antigen, CA 125, were measured by a monoclonal antibody (MAb)-based double determinant immunoradiometric assay (IRMA) in patients who developed antibodies to mouse immunoglobulins (IgGs) after receiving injections of the same MAb as is used in the CA 125 IRMA. Addition of undiluted mouse serum or purified mouse IgG to the assay mixture failed to eliminate the falsely increased CA 125 concentrations in most of the samples, owing to the presence of anti-idiotype antibody. Because of their anti-idiotypic nature, the human anti-mouse antibodies (HAMAS) had only little effect on other immunometric assays, and this effect could be completely eliminated by addition of mouse IgG. To eliminate the effect of HAMA on the CA 125 assay, we studied the ability of various chromatographic methods to separate the interfering HAMA from CA 125. For measuring HAMA in serum and chromatographic fractions we developed a time-resolved fluoroimmunoassay. Adequate separation of CA 125 and HAMA was achieved by affinity chromatography of patients' sera with solid-phase Protein A, Protein G, cation-exchange chromatography on Mono S, and gel filtration on Superose 6. These results demonstrate that the interference can effectively be removed by rather simple chromatographic procedures.

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Williard, Clark V. "Bioanalytical method transfer considerations of chromatographic-based assays." Bioanalysis 8, no. 13 (July 2016): 1409–13. http://dx.doi.org/10.4155/bio.16.34.

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Johns, Margaret A., Laura K. Rosengarten, Martha Jackson, and Fred E. Regnier. "Enzyme-linked immunosorbent assays in a chromatographic format." Journal of Chromatography A 743, no. 1 (August 1996): 195–206. http://dx.doi.org/10.1016/0021-9673(96)00370-6.

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Londhe, Vaishali, and Madhura Rajadhyaksha. "Review of Recommendations for Bioanalytical Method Validation: Chromatographic Assays and Ligand Binding Assays." Chromatographia 82, no. 2 (December 19, 2018): 523–35. http://dx.doi.org/10.1007/s10337-018-3677-z.

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Coleman, Mark R., Thomas D. Macy, John W. Morgan, and J. Matthew Rodewald. "Ruggedness of the Monensin and Narasin Liquid Chromatographic Assays." Journal of AOAC INTERNATIONAL 77, no. 5 (September 1, 1994): 1065–72. http://dx.doi.org/10.1093/jaoac/77.5.1065.

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Abstract Supplementary validation data were generated for the monensin and narasin liquid chromatographic (LC) assays. Several parameters of the LC system and the sample preparation procedures were evaluated. Feed samples are routinely extracted in meth-anol-water (9 + 1, v/v). The ratio of methanol to water was varied to evaluate the ruggedness of the extraction procedure. The LC parameters evaluated included flow rates of the mobile phase and vanillin reagent, reactor temperature, and water content of the mobile phase. The resolution of monensin A, monensin B, and narasin A; retention times; tailing factors; peak areas; and peak widths were monitored as LC parameters were varied. The stabilities of monensin and narasin reference standard solutions over time when stored at room temperature and under refrigeration were also monitored. The results show that deviations in the methanol-water ratio of the extraction solution did not significantly affect final assay results. Modification of LC parameters may substantially affect retention time, peak area, and resolution factors.

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Vidal-Casanella, Oscar, Javier Moreno-Merchan, Merce Granados, Oscar Nuñez, Javier Saurina, and Sonia Sentellas. "Total Polyphenol Content in Food Samples and Nutraceuticals: Antioxidant Indices versus High Performance Liquid Chromatography." Antioxidants 11, no. 2 (February 7, 2022): 324. http://dx.doi.org/10.3390/antiox11020324.

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Total polyphenol content and antioxidant capacity were estimated in various food and nutraceutical samples, including cranberries, raspberries, artichokes, grapevines, green tea, coffee, turmeric, and other medicinal plant extracts. Samples were analyzed by using two antioxidant assays—ferric reducing antioxidant power (FRAP) and Folin–Ciocalteu (FC)—and a reversed-phase high-performance liquid chromatography (HPLC), with a focus on providing compositional fingerprints dealing with polyphenolic compounds. A preliminary data exploration via principal component analysis (PCA) revealed that HPLC fingerprints were suitable chemical descriptors to classify the analyzed samples according to their nature. Moreover, chromatographic data were correlated with antioxidant data using partial least squares (PLS) regression. Regression models have shown good prediction capacities in estimating the antioxidant activity from chromatographic data, with determination coefficients (R2) of 0.971 and 0.983 for FRAP and FC assays, respectively.

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Moraes, Marcela Cristina, Carmen Cardoso, Cláudia Seidl, Ruin Moaddel, and Quezia Cass. "Targeting Anti-Cancer Active Compounds: Affinity-Based Chromatographic Assays." Current Pharmaceutical Design 22, no. 39 (December 14, 2016): 5976–87. http://dx.doi.org/10.2174/1381612822666160614080506.

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Marquina, C., J. M. de Teresa, D. Serrate, J. Marzo, F. A. Cardoso, D. Saurel, S. Cardoso, P. P. Freitas, and M. R. Ibarra. "GMR sensors and magnetic nanoparticles for immuno-chromatographic assays." Journal of Magnetism and Magnetic Materials 324, no. 21 (October 2012): 3495–98. http://dx.doi.org/10.1016/j.jmmm.2012.02.074.

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Puopolo, P. R., and J. G. Flood. "Detection of interference by cyclobenzaprine in liquid-chromatographic assays of tricyclic antidepressants." Clinical Chemistry 33, no. 6 (June 1, 1987): 819–20. http://dx.doi.org/10.1093/clinchem/33.6.819.

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Abstract We evaluated a technique for detecting cyclobenzaprine interference with liquid-chromatographic assays for tricyclic antidepressants. The technique involves dual-wavelength absorbance monitoring of the column effluent at 214 and 254 nm. Ratios of analyte peak heights at each wavelength are used to check for the presence of co-eluting interferences. With this technique, one can detect interference with an amitriptyline assay caused by 10 micrograms of cyclobenzaprine per liter.

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Fitzgerald, R. L., and D. A. Herold. "Serum total testosterone: immunoassay compared with negative chemical ionization gas chromatography-mass spectrometry." Clinical Chemistry 42, no. 5 (May 1, 1996): 749–55. http://dx.doi.org/10.1093/clinchem/42.5.749.

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Abstract We have developed an electron capture negative chemical ionization gas chromatography-mass spectrometry (GC-MS) procedure to quantify serum testosterone in the clinically relevant range 0.69-69.3 nmol/L and used this procedure to assess Ciba Corning Diagnostics ACS:180 testosterone immunoassay. The GC-MS method involves liquid-liquid extraction of serum samples and synthesis of a pentafluorobenzyloxime/silyl ether derivative of testosterone with excellent chromatographic and electron capturing properties. The ACS testosterone assay is the first fully automated nonradioactive testosterone immunoassay approved by the US Food and Drug Administration. Patients' specimens (101, 57 males, 44 females) were analyzed by both techniques. A plot of the GC-MS (x) vs ACS (y) testosterone concentrations for men was linear (y = 1.07x + 0.19 nmol/L), showing excellent correlation (r2 = 0.98) between the two assays. Agreement of the two assays for female specimens was poor (y = 0.72x + 1.2 nmol/L), with a poor correlation (r2 = 0.31).

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Sohl, Christal D., Qian Cheng, and F. Peter Guengerich. "Chromatographic assays of drug oxidation by human cytochrome P450 3A4." Nature Protocols 4, no. 9 (August 6, 2009): 1252–57. http://dx.doi.org/10.1038/nprot.2009.122.

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15

MEDINA, MARJORIE B., ROBERT A. BARFORD, MARY S. PALUMBO, and LOYD D. ROWE. "Evaluation of Commercial Immunochemical Assays for Detection of Sulfamethazine in Milk." Journal of Food Protection 55, no. 4 (April 1, 1992): 284–90. http://dx.doi.org/10.4315/0362-028x-55.4.284.

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Sulfamethazine (SMZ) is effective in the treatment of bacterial infections in food producing animals but its use is prohibited in dairy cows. Nevertheless, a 1988 survey of milk in ten cities conducted by the Food and Drug Administration revealed the presence of SMZ. Therefore, it was apparent that there was a need for rapid screening methods for SMZ. We evaluated commercial immunochemical test kits for SMZ with detectabilities of 1–10 parts per billion (ppb). Manipulations are suggested to effectively optimize immunochemical detection of SMZ in raw and processed fluid milk. The performances of the enzyme immunochemical test kits were evaluated by studying the effects of sample preparation, sample matrix, calibration and detection range of the kits using raw and processed milk samples. Immunochemical results were compared to quantitative high performance thin layer chromatography and high performance liquid chromatography with electrochemical detection. Both chromatographic methods had detectabilities in the low parts per billion range.

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Petkova, Mariana, and Nadezhda Sertova. "Detection of mycotoxins trough different analytical methods." Zbornik Matice srpske za prirodne nauke, no. 134 (2018): 43–54. http://dx.doi.org/10.2298/zmspn1834043p.

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Mycotoxins are secondary metabolites produced by fungi which can affect a variety of feedstuffs. These compounds elicit toxicological effects which represent risk for both humans and animals. Their toxicity occurs at very low concentrations, therefore there is a need for sensitive and reliable methods for their detection. This review aims to evaluate classical and emerging methods for the analysis of mycotoxins concerning their advantages and disadvantages. Currently, several sensitive methods based on chromatographic or immunochemical technique are commercially available. Especially widely are used different chromatographic methods for quantitative determination of mycotoxins, including gas-chromatography (GC) and high-performance liquid chromatography (HPLC) coupled with ultraviolet, fluorescence or MS detectors. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) is used as a promising technique for screening, identification and quantitative determination of a large number of mycotoxins. Immunometric assays, such as enzyme-linked immunosorbent assays (ELISA), are frequently used for screening purposes. On the other hand, a variety of emerging methods have been proposed. They are based on novel technologies, including immunochromatography (i.e. lateral flow devices), fluorescence polarization immunoassays (FPIA), infrared spectroscopy (FT-NIR), molecularly imprinted polymers (MIPs), and optical biosensors. In addition, during the last years, the highlight was put on nanoscale materials included in biosensors, which are some of the smart devices used for determination of mycotoxins.

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Shah, Iltaf, Mohammad Mansour, Sheikh Jobe, Emadaldeen Salih, Declan Naughton, and Syed Salman Ashraf. "A Non-Invasive Hair Test to Determine Vitamin D3 Levels." Molecules 26, no. 11 (May 28, 2021): 3269. http://dx.doi.org/10.3390/molecules26113269.

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Vitamin D deficiency is being recognized as a global issue and has been implicated in many health issues. Hence, there is an increased interest in developing sensitive, reproducible, and non-invasive assays to measure Vitamin D levels. This study aimed to apply a sensitive liquid chromatography-mass spectrometric assay to hair samples to develop and validate a clinical assay to provide a quarterly average level of vitamin D in one test. Hair samples were collected from 70 male university students/young adults and pulverized/sonicated in methanol/water for 2 h to extract Vitamin D metabolites. A sensitive liquid chromatographic-mass spectrometric assay was employed to quantitate vitamin D and metabolites. Of the eight Vitamin D and metabolites screened, only the primary, clinically significant form of vitamin D (25OHD3) was detected and quantified in hair samples in the range of 17–1541 pg/mg. One-third of the hair samples (21 out of 70) had Vitamin D levels below the LLOD of the assay (10 pg/mg). The mean and standard deviation values for hair (25OHD3) were 276.7 ± 329.9, respectively. This pilot study reveals the potential of the vitamin D hair test in clinical assays as a complementary test to a vitamin D blood test, which would provide a quarterly average.

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Rowe, David J. F., Ian D. Watson, John Williams, and David J. Berry. "The Clinical Use and Measurement of Theophylline." Annals of Clinical Biochemistry: International Journal of Laboratory Medicine 25, no. 1 (January 1988): 4–26. http://dx.doi.org/10.1177/000456328802500102.

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This report reviews the clinical use, metabolism and toxicity of theophylline (Section 1). Current chromatographic and immunoassay methods for theophylline measurement are discussed and practical methods using high-performance liquid chromatography are described (Section 2). Results from the UK National scheme for theophylline quality control and from an experiment to investigate the degree of interference by 1,7-dimethylxanthine in routine assays for theophylline are discussed in Section 3.

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Hynning, P. A., P. Anderson, U. Bondesson, and L. O. Boréus. "Liquid-chromatographic quantification compared with gas-chromatographic-mass-spectrometric determination of verapamil and norverapamil in plasma." Clinical Chemistry 34, no. 12 (December 1, 1988): 2502–3. http://dx.doi.org/10.1093/clinchem/34.12.2502.

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Abstract A high-performance liquid chromatographic (HPLC) method for determining verapamil and norverapamil in plasma is presented and compared with gas chromatography/mass spectrometry (GC-MS). The plasma samples were extracted at alkaline pH with hexane containing 2-butanol (20 mL/L) and then back-extracted into phosphate buffer (0.1 mol/L, pH 3.0). For chromatography we used a reversed-phase column (Supelcosil LC-18 DB) with a mobile phase of the phosphate buffer and acetonitrile (70/30 by vol). Fluorescence detection was used (excitation at 203 nm, emission at 320 nm). Overall analytical recovery was 85%. Standard curves were linear from 1 to 1000 micrograms/L. The detection limit was 1 microgram/L. The assays are accurate and precise. We found no interferences by those substances tested. Results by HPLC and GC-MS agreed well (r = 0.99) for both verapamil and norverapamil determinations.

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Haroon, Y., D. S. Bacon, and J. A. Sadowski. "Liquid-chromatographic determination of vitamin K1 in plasma, with fluorometric detection." Clinical Chemistry 32, no. 10 (October 1, 1986): 1925–29. http://dx.doi.org/10.1093/clinchem/32.10.1925.

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Abstract This assay for phylloquinone (vitamin K1) in plasma requires a single liquid-chromatographic step. Much smaller volumes of plasma (0.5-1.0 mL) are required than in previous assays. Before liquid chromatography, we purified crude lipid extracts by conventional chromatography on silica, then extracted the lipid fraction by dissolving it in an acidic mixture of hexane/acetonitrile (1/4 by vol) containing 70 mmol of zinc chloride per liter. The vitamin K1 was selectively extracted into acetonitrile after being converted to vitamin K1 hydroquinone by addition of zinc metal. This procedure removes greater than 99% of contaminating lipids. We injected the lipid extract directly onto a reversed-phase column after re-converting the vitamin K1 hydroquinone to vitamin K1. Vitamin K1 was quantified by comparison with the internal standard (dihydro-vitamin K1) and detected fluorometrically after post-column "on-line" reduction to the hydroquinone with zinc metal. The lower limit of detection for vitamin K1 in the final reversed-phase system was about 0.05 microgram/L plasma; CVs for replicates were less than 10%. The mean concentration of vitamin K1 in plasma from 22 healthy fasting adults was 0.55 (range 0.09-2.12) micrograms/L.

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Reepmeyer, John C., and Don C. Cox. "Liquid Chromatographic Determination of Thalidomide in Tablets, Capsules, and Raw Materials." Journal of AOAC INTERNATIONAL 80, no. 4 (July 1, 1997): 767–74. http://dx.doi.org/10.1093/jaoac/80.4.767.

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Abstract A simple, isocratic liquid chromatographic method for assay of thalidomide in tablets, capsules, and raw materials was developed. The method uses a Nova-Pak octadecylsilane bonded-phase column (150 × 3.9 mm, 4 μm particle size), a mobile phase of acetonitrile-water (15 + 85), a flow rate of 1 mL/min, detection at 237 nm, and phenacetin as internal standard. Phosphoric acid was used in preparation of sample solutions to inhibit thalidomide hydrolysis. Assays ranged from 99.3 to 100.4% in raw materials from 4 manufacturers, from 79.7 to 104.8% in tablets from 7 manufacturers, and from 75.3 to 102.6% in capsules from 4 manufacturers. Assay method precisions for triplicate analyses on 5 days were 0.30% for tablets, 0.22% for capsules, and 0.22% for raw materials. Recovery from simulated tablet formulations was 100%. The method has been used to analyze individual tablets and capsules for determination of content uniformity.

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Sachsenmeier, Kris F., Carl Hay, Erin Brand, Lori Clarke, Kim Rosenthal, Sandrine Guillard, Steven Rust, Ralph Minter, and Robert Hollingsworth. "Development of a Novel Ectonucleotidase Assay Suitable for High-Throughput Screening." Journal of Biomolecular Screening 17, no. 7 (April 20, 2012): 993–98. http://dx.doi.org/10.1177/1087057112443987.

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5′-Ectonucleotidase (NT5E) catalyzes the conversion of adenosine monophosphate to adenosine and free phosphate. The role of this ectonucleotidase and its production of adenosine are linked with immune function, angiogenesis, and cancer. NT5E activity is typically assayed either by chromatographic quantification of substrates and products using high-performance liquid chromatography (HPLC) or by quantification of free phosphate using malachite green. These methods are not suitable for robust screening assays of NT5E activity. HPLC is not readily suitable for the rapid and efficient assay of multiple samples and malachite green is highly sensitive to the phosphate-containing buffers common in various media and sample buffers. Here the development and validation of a novel high-throughput ectonucleotidase screening assay are described, which makes use of a luciferase-based assay reagent, the Promega CellTiter-Glo kit, to measure the catabolism of AMP by NT5E. This multiwell plate-based assay facilitates the screening of potential ectonucleotidase antagonists and is unaffected by the presence of contaminating phosphate molecules present in screening samples.

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Verhaeghe, Tom. "Systematic internal standard variability and issue resolution: two case studies." Bioanalysis 11, no. 18 (September 2019): 1685–92. http://dx.doi.org/10.4155/bio-2019-0165.

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Two case studies are presented of validated assays where the internal standard showed high variability, and there was a clear response difference between study samples and standards and quality controls. In the first case a co-eluting peak boosted the stable isotope labeled internal standard response in samples from hepatically impaired subjects. In the second case the blank plasma matrix suppressed the structural analog internal standard response. For both assays the issue could be resolved by adapting the chromatographic conditions and re-validating the assay (case 1) or by diluting the study samples with blank plasma (case 2).

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Coleman, Mark R., John W. Moran, Daniel H. Mowrey, J. P. Antalick, D. J. Bark, D. A. Bridges, N. L. Britton, et al. "Liquid Chromatographic Determination of Monensin in Premix and Animal Feeds: Collaborative Study." Journal of AOAC INTERNATIONAL 80, no. 4 (July 1, 1997): 693–702. http://dx.doi.org/10.1093/jaoac/80.4.693.

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Abstract An interlaboratory study of a liquid chromatographic (LC) method for determining monensin in premix (60–80 g/lb or 132–5176 mg/g) and animal feeds (5–200 g/ton or 0.0055–0.22 mg/g) was conducted in laboratoriesin the United States, Canada, France, and Germany. The LC system used a reversed- phase column, postcolumn derivatization with vanillin, and UV detection. The method separates monensin from other ionophores such as narasin and salinomycin. Each laboratory analyzed a total of 20 samples of premix, liquid feed supplements, poultry, and cattle feeds. Concentrations of monensin in all samples ranged from 0 to 176 mg/g (80 g/lb). Reproducibility relative standard deviation (RSDR) for premix ranged from 2.8 to 3.4%. For feed samples containing monensin, repeatability standard deviation (Sr) ranged from 0.9 to 7.0. Reproducibility standard deviation (SR) ranged from 1.2 to 11. Repeatability relative standard deviation (RSDr) ranged from 6.1 to 21% and RSDR valuesranged from 8.6 to 25%. Sample preparation for the LC method is less labor intensive than that for the microbiological assays. The LC assay is more efficient than the microbiological assays. This LC method for determination of monensin in premix and animal feeds has been adopted first action by AOAC INTERNATIONAL.

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Wang, Laixin, Min Meng, and Scott Reuschel. "Regulated bioanalysis of oligonucleotide therapeutics and biomarkers: qPCR versus chromatographic assays." Bioanalysis 5, no. 22 (November 2013): 2747–51. http://dx.doi.org/10.4155/bio.13.234.

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Hughes, Nicola C., Ernest Y. K. Wong, Juan Fan, and Navgeet Bajaj. "Determination of carryover and contamination for mass spectrometry-based chromatographic assays." AAPS Journal 9, no. 3 (September 2007): E353—E360. http://dx.doi.org/10.1208/aapsj0903042.

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Retmana, Irene A., Jos H. Beijnen, and Rolf W. Sparidans. "Chromatographic bioanalytical assays for targeted covalent kinase inhibitors and their metabolites." Journal of Chromatography B 1162 (January 2021): 122466. http://dx.doi.org/10.1016/j.jchromb.2020.122466.

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Bethune, C., T. Bui, M. L. Liu, M. A. Kay, and R. J. Ho. "Development of a high-performance liquid chromatographic assay for G418 sulfate (Geneticin)." Antimicrobial Agents and Chemotherapy 41, no. 3 (March 1997): 661–64. http://dx.doi.org/10.1128/aac.41.3.661.

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We have developed a chromatographic assay with high sensitivity and specificity to quantify G418 sulfate (Geneticin), an antibiotic used routinely in molecular genetics experiments for selecting eukaryotic transformants. With this method, G418 in tissues and plasma samples can be quantitated without the confounding factors often associated with biological assays. After removal of proteins in homogenized tissue or plasma samples with methanol (2:1, vol/vol), the amino group of G418 was derivatized with 1-fluoro-2,4-dinitrobenzene (DNFB) to form the UV-visible G418-DNFB product. The DNFB-derivatized G418 was separated on a reversed-phase C18 column with an acetonitrile and water gradient as the mobile phase. Under these assay conditions, the detection limit for G418 sulfate in buffer, plasma, and tissues was recorded at 78 ng/ml and the linearity was recorded for concentrations up to 100 micrograms/ml. The data obtained from this analysis indicate that this assay can be used for the quantitative determination of G418 sulfate in plasma and tissue samples.

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Hamdy, Dalia A., and Tarek S. Belal. "A Comparative Study of Newly Developed HPLC-DAD and UHPLC-UV Assays for the Determination of Posaconazole in Bulk Powder and Suspension Dosage Form." Journal of Analytical Methods in Chemistry 2014 (2014): 1–7. http://dx.doi.org/10.1155/2014/241035.

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Objective. To develop and compare HPLC-DAD and UHPLC-UV assays for the quantitation of posaconazole in bulk powder and suspension dosage form.Methods. Posaconazole linearity range was 5–50 μg/mL for both assays. For HPLC-DAD assay, samples were injected through Zorbax SB-C18 (4.6 × 250 mm, 5 μm) column. The gradient elution composed of the mobile phase acetonitrile: 15 mM potassium dihydrogen orthophosphate (30 : 70 to 80 : 20, linear over 7 minutes) pumped at 1.5 mL/min. For UHPLC-UV assay, samples were injected through Kinetex-C18 (2.1 × 50 mm, 1.3 μm) column. The mobile phase composed of acetonitrile: 15 mM potassium dihydrogen orthophosphate (45 : 55) pumped isocratically at 0.4 mL/min. Detection wavelength was 262 nm in both methods.Results. The run time was 11 and 3 minutes for HPLC-DAD and UHPLC-UV assays, respectively. Both assays were linear (r2>0.999) with CV% and % error of the mean <3%. Limits of detection and quantitation were 0.82 and 2.73 μg/mL for HPLC-DAD and 1.04 and 3.16 μg/mL for UHPLC-UV, respectively. The methods quantitated PSZ in suspension dosage form with no observable interferences.Conclusions. Both assays were proven sensitive and selective according to ICH guidelines. UHPLC-UV assay exhibited some economic and chromatographic separation superiority.

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Martins, Fernanda O., Patricia F. Esteves, Gabriella S. Mendes, Nanci S. Barbi, Fabio S. Menezes, and Maria T. V. Romanos. "Verbascoside isolated from Lepechinia speciosa has inhibitory Activity against HSV-1 and HSV-2 in vitro." Natural Product Communications 4, no. 12 (December 2009): 1934578X0900401. http://dx.doi.org/10.1177/1934578x0900401217.

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Verbascoside has been isolated form L. speciosa after several different chromatographic methods. After its purification, the structure has been unequivocally established using modern spectroscopic techniques. As for the antiviral activity, the maximum non toxic concentration has been established and this concentration has been used in the anti herpes assay, in vitro. Mechanism of action for this molecule regarding the anti-herpes activity has been studied encompassing the following assays: virucidal activity, cellular receptor assay, penetration assay and intracellular assay, in order to understand the activity for this natural product.

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Xie, Yulu, Xican Li, Jingyu Chen, Yuman Deng, Wenbiao Lu, and Dongfeng Chen. "pH Effect and Chemical Mechanisms of Antioxidant Higenamine." Molecules 23, no. 9 (August 29, 2018): 2176. http://dx.doi.org/10.3390/molecules23092176.

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In this article, we determine the pH effect and chemical mechanism of antioxidant higenamine by using four spectrophotometric assays: (1) 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide radical (PTIO•)-scavenging assay (at pH 4.5, 6.0, and 7.4); (2) Fe3+-reducing power assay; (3) Cu2+-reducing power assay; and (4) 1,1-diphenyl-2-picryl-hydrazyl (DPPH•)-scavenging assay. The DPPH•-scavenging reaction product is further analyzed by ultra-performance liquid chromatography, coupled with electrospray ionization quadrupole time-of-flight tandem mass spectrometry (UPLC-ESI-Q-TOF-MS/MS) technology. In the four spectrophotometric assays, higenamine showed good dose-response curves; however, its IC50 values were always lower than those of Trolox. In UPLC-ESI-Q-TOF-MS/MS analysis, the higenamine reaction product with DPPH• displayed three chromatographic peaks (retention time = 0.969, 1.078, and 1.319 min). The first gave m/z 541.2324 and 542.2372 MS peaks; while the last two generated two similar MS peaks (m/z 663.1580 and 664.1885), and two MS/MS peaks (m/z 195.9997 and 225.9971). In the PTIO•-scavenging assays, higenamine greatly decreased its IC50 values with increasing pH. In conclusion, higenamine is a powerful antioxidant—it yields at least two types of final products (i.e., higenamine-radical adduct and higenamine-higenamine dimer). In aqueous media, higenamine may exert its antioxidant action via electron-transfer and proton-transfer pathways. However, its antioxidant action is markedly affected by pH. This is possibly because lower pH value weakens its proton-transfer pathway via ionization suppression by solution H+, and its electron-transfer pathway by withdrawing the inductive effect (-I) from protonated N-atom. These findings will aid the correct use of alkaloid antioxidants.

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Barfield, Matthew, Joanne Goodman, John Hood, and Philip Timmerman. "European Bioanalysis Forum recommendation on singlicate analysis for ligand binding assays: time for a new mindset." Bioanalysis 12, no. 5 (March 2020): 273–84. http://dx.doi.org/10.4155/bio-2019-0298.

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It is well accepted that chromatographic assay methods employ singlicate analysis for toxicokinetic and pharmacokinetic analysis. While conversely, it has been the norm for ligand-binding assays to be run in at least duplicate analyses, stemming mainly from concerns over inherent assay variability and reagent quality. Regulatory guidelines and guidance on bioanalytical method validation has, in the most part, recommended multiple replicates for immunoassays and this has led to the industry being comfortable and familiar with duplicate analysis. Over the last few years, the discussion on whether singlicate analysis is acceptable for ligand-binding assays has grown and the status quo is being challenged for regulated bioanalysis performed using immunoassays. Through interrogation of preclinical and clinical pharmacokinetic assay data from the European Bioanalysis Forum community, the application of a singlicate analysis strategy has shown to have no impact on toxicokinetic and pharmacokinetic parameters when compared with duplicate analysis from the same studies. Therefore, now is the time to adopt a new mindset when it comes to sample analysis for toxicokinetic and pharmacokinetic ligand-binding assays and embrace singlicate analysis in the regulated environment.

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Berg, A. H., and D. B. Sacks. "Haemoglobin A1c analysis in the management of patients with diabetes: from chaos to harmony: Table 1." Journal of Clinical Pathology 61, no. 9 (August 28, 2008): 983–87. http://dx.doi.org/10.1136/jcp.2007.049205.

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Effective management of patients with diabetes mellitus requires accurate assessments of blood glucose control. The best characterised marker of long term glycaemic control is whole blood haemoglobin A1c (HbA1c). Published clinical trials have identified quantitative and direct relationships between the HbA1c concentration and risks of diabetic microvascular complications. However, in order to practice evidence-based medicine, assays used to measure patient samples should ideally produce values comparable to the assays used in these trials. Numerous assays using chromatographic and immunological detection methods are used around the world. This paper briefly reviews the scientific evolution of HbA1c and its analysis, discusses the reasons why HbA1c assay standardisation is a challenge, describes the approaches that have been adopted to harmonise HbA1c assays, and addresses the current initiatives to standardise HbA1c globally. These efforts have established HbA1c as an essential component in the management of patients with diabetes mellitus and are likely to lead to the use of HbA1c in the screening/diagnosis of diabetes.

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Adewusi, Emmanuel Adekanmi, Paul Steenkamp, Gerda Fouche, and Vanessa Steenkamp. "Isolation of Cycloeucalenol from Boophone Disticha and Evaluation of its Cytotoxicity." Natural Product Communications 8, no. 9 (September 2013): 1934578X1300800. http://dx.doi.org/10.1177/1934578x1300800906.

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Boophone disticha (Amaryllidaceae) is widely used in traditional medicine in southern Africa. Several alkaloids, volatile oils and fatty acids have been isolated from the plant. However, there has been no literature report of a triterpene from B. disticha. Cycloeucalenol, a cycloartane triterpene, together with its regio-isomer, was isolated from the ethyl acetate extract of the bulbs using column chromatography and preparative thin layer chromatography. Structural elucidation was carried out using 1D and 2D NMR and mass spectroscopy. The MTT and neutral red assays were used to assess the cytotoxicity of the compound in human neuroblastoma (SH-SY5Y) cells. The compound was obtained as a mixture of two regio-isomers, which were separated for the first time by chromatographic optimization. Integration of the 1H NMR spectrum showed that cycloeucalenol and its regio-isomer were present in a ratio of 1.04:1. A dose-dependent decrease in cell viability was observed using both cytotoxicity assays. IC50 values of 173.0 ± 5.1 μM and 223.0 ± 6.4 μM were obtained for the MTT and neutral red assays, respectively, indicative of the low toxicity of the compound. This work describes for the first time, the presence of triterpene compounds from the genus Boophone.

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Dias, Albino A., António J. S. Matos, Irene Fraga, Ana Sampaio, and Rui M. F. Bezerra. "An Easy Method for Screening and Detection of Laccase Activity." Open Biotechnology Journal 11, no. 1 (September 14, 2017): 89–93. http://dx.doi.org/10.2174/1874070701711010089.

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Objective: An instrument-free assay was developed for simultaneous detection of laccase activity in a large number of samples as diverse as screening of laccase-producing microbial cultures or chromatographic fractions. Method: Dried paper discs previously impregnated with 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) were placed on a flat-bottom microplate (a simple way to avoid misidentification) and loaded with an aliquot from each sample. Results: Discs corresponding to samples containing laccase activity become green-bluish colored within first ten minutes of reaction, allowing direct detection through simple naked-eye inspection. Conclusion: As an example, this easy process was applied to the laccase purification in order to eliminate chromatographic fractions that did not contain laccase activity, thus reducing the number of spectrophotometric assays.

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Jamalova, Dilafruz N., Haidy A. Gad, Davlat K. Akramov, Komiljon S. Tojibaev, Nawal M. Al Musayeib, Mohamed L. Ashour, and Nilufar Z. Mamadalieva. "Discrimination of the Essential Oils Obtained from Four Apiaceae Species Using Multivariate Analysis Based on the Chemical Compositions and Their Biological Activity." Plants 10, no. 8 (July 26, 2021): 1529. http://dx.doi.org/10.3390/plants10081529.

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The chemical composition of the essential oils obtained from the aerial parts of four Apiaceae species, namely Elaeosticta allioides (EA), E. polycarpa (EP), Ferula clematidifolia (FC), and Hyalolaena intermedia (HI), were determined using gas chromatography. Altogether, 100 volatile metabolites representing 78.97, 81.03, 85.78, and 84.49% of the total components present in EA, EP, FC, and HI oils, respectively, were reported. allo-Ocimene (14.55%) was the major component in FC, followed by D-limonene (9.42%). However, in EA, germacrene D (16.09%) was present in a high amount, while heptanal (36.89%) was the predominant compound in HI. The gas chromatographic data were subjected to principal component analysis (PCA) to explore the correlations between these species. Fortunately, the PCA score plot could differentiate between the species and correlate Ferula to Elaeosticta species. Additionally, the antioxidant activity was evaluated in vitro using the 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH), 2,2-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS), and the ferric reducing power (FRAP) assays. In addition, the antimicrobial activity using the agar diffusion method was assessed, and the minimum inhibitory concentrations (MICs) were determined. Furthermore, the cell viability MTT assay was performed to evaluate the cytotoxicity of the essential oils against hepatic (HepG-2) and cervical (HeLa) cancer cell lines. In the DPPH assay, FC exhibited the maximum activity against all the antioxidant assays with IC50 values of 19.8 and 23.0 μg/mL for the DPPH and ABTS assays, respectively. Ferula showed superior antimicrobial and cytotoxic activities as well. Finally, a partial least square regression model was constructed to predict the antioxidant capacity by utilizing the metabolite profiling data. The model showed excellent predictive ability by applying the ABTS assay.

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Van Hoey, Nicole M. "Effect of Cyclobenzaprine on Tricyclic Antidepressant Assays." Annals of Pharmacotherapy 39, no. 7-8 (July 2005): 1314–17. http://dx.doi.org/10.1345/aph.1e632.

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OBJECTIVE To evaluate cyclobenzaprine interference on tricyclic antidepressant assays. DATA SOURCES Literature was identified through a MEDLINE search (1966–August 2004) using the search terms cyclobenzaprine, tricyclic antidepressant, toxicology, and assay. DATA SYNTHESIS Cyclobenzaprine is structurally similar to tricyclic antidepressants and is often identified as a tricyclic antidepressant on toxicology assays. Older chromatographic assays demonstrate retention time differences of only seconds and nearly identical color stains between cyclobenzaprine and individual tricyclic antidepressants. In comparison, ultraviolet absorption ratios of 4.18 for amitriptyline and 1.85 for cyclobenzaprine are easily distinguished. Spectroscopy also consistently identifies cyclobenzaprine's unique mass-to-charge ratio peaks of 275 and 215 compared with those of amitriptyline. Available bioanalytic techniques are reviewed for their ability to correctly identify cyclobenzaprine and differentiate the drug from tricyclic antidepressants. CONCLUSIONS When assays are positive for tricyclic antidepressants without a history of their use, an attempt should be made to identify confounders, such as cyclobenzaprine. Newer bioanalytic techniques, such as ultraviolet absorption and mass spectroscopy, accurately identify cyclobenzaprine in such instances.

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Valenti, Leonard P., and Cesar A. Lau-Cam. "Reverse Phase Liquid Chromatographic Determination of Bisacodyl in Dosage Forms." Journal of AOAC INTERNATIONAL 68, no. 3 (May 1, 1985): 529–32. http://dx.doi.org/10.1093/jaoac/68.3.529.

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Abstract A method is described for the determination of bisacodyl in entericcoated tablets and suppositories by liquid chromatography (LC). The method will also determine the hydrolysis degradation products monoacetylbisacodyl and desacetylbisacodyl. The sample is dissolved in 2- propanol, and the extract is diluted with the mobile phase and injected into a liquid chromatograph fitted with a μBondapak C18 column and an ultraviolet detector set at 254 nm. The column is eluted with methanol- acetonitrile-0.01M citric acid (25 + 25 + 50). The pooled mean recovery value for bisacodyl from commercial enteric-coated tablets and suppositories was 99.7 % with a pooled coefficient of variation (CV) of 0.72%. For content uniformity assays, the CVs were 0.7 and 1.0% for groups of 10 individual commercial suppositories and tablets, respectively. Differences between assay values by the LC and USP XX methods were 0.2% of declared for enteric-coated tablets (n = 5) and 1.0% of declared for suppositories (n = 2). The LC method can determine as little as 0.015 μg of the monoacetyl or desacetyl degradation product.

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HAYASHI, Yuzuru, and Rieko MATSUDA. "Information theory of precision and analytical efficiency in short-column chromatographic assays." Analytical Sciences 7, no. 2 (1991): 329–31. http://dx.doi.org/10.2116/analsci.7.329.

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Vander Heyden, Y., J. Saevels, E. Roets, J. Hoogmartens, D. Decolin, M. G. Quaglia, W. Van den Bossche, et al. "Interlaboratory studies on two high-performance liquid chromatographic assays for tylosin (tartrate)." Journal of Chromatography A 830, no. 1 (January 1999): 3–28. http://dx.doi.org/10.1016/s0021-9673(98)00840-1.

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Jeffries, Thomas W., Vina W. Yang, and Mark W. Davis. "Comparative study of xylanase kinetics using dinitrosalicylic, arsenomolybdate, and ion chromatographic assays." Applied Biochemistry and Biotechnology 70-72, no. 1 (March 1998): 257–65. http://dx.doi.org/10.1007/bf02920142.

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Cox, Raymond A., Kathryn N. McFarland, Patricia Holt Sackett, and Michael T. Short. "Correlation of urokinase activity from biopotency and high-performance liquid chromatographic assays." Journal of Chromatography A 370 (January 1986): 495–500. http://dx.doi.org/10.1016/s0021-9673(00)94719-8.

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Gebicki, Janusz M., and Jennifer Guille. "Spectrophotometric and high-performance chromatographic assays of hydroperoxides by the iodometric technique." Analytical Biochemistry 176, no. 2 (February 1989): 360–64. http://dx.doi.org/10.1016/0003-2697(89)90323-0.

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Al-Amin, Mohammad, Nagla Mustafa Eltayeb, Chowdhury Faiz Hossain, Melati Khairuddean, Siti Sarah Fazalul Rahiman, and Salizawati Muhamad Salhimi. "Inhibitory Activity of Extract, Fractions, and Compounds from Zingiber montanum Rhizomes on the Migration of Breast Cancer Cells." Planta Medica 86, no. 06 (March 13, 2020): 387–94. http://dx.doi.org/10.1055/a-1129-7026.

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Abstract Zingiber montanum rhizomes are traditionally used for the treatment of numerous human ailments. The present study was carried out to investigate the inhibitory activity of the crude extract, chromatographic fractions, and purified compounds from Z. montanum rhizomes on the migration of MDA-MB-231 cells. The effect of the extract on cell migration was investigated by a scratch assay, which showed significant inhibition in a concentration-dependent manner. Vacuum liquid chromatography on silica gel afforded four fractions (Frs. 1 – 4), which were tested on cell migration in the scratch assay. Frs. 1 and 2 showed the most significant inhibition of MDA-MB-231 cell migration. The effect of the most potent fraction (Fr. 2) was further confirmed in a transwell migration assay. The study of Frs. 1 and 2 by gelatin zymography showed significant inhibition of MMP-9 enzyme activity. Chromatographic separation of Frs. 1 and 2 afforded buddledone A (1), zerumbone (2), (2E,9E)-6-methoxy-2,9-humuradien-8-one (3), zerumbone epoxide (4), stigmasterol (5), and daucosterol (6). In a cell viability assay, compounds 1 – 4 inhibited the viability of MDA-MB-231 cells in a concentration-dependent manner. The study of buddledone A (1) and zerumbone epoxide (4) on cell migration revealed that 4 significantly inhibited the migration of MDA-MB-231 cells in both scratch and transwell migration assays. The results of the present study may lead to further molecular studies behind the inhibitory activity of zerumbone epoxide (4) on cell migration and support the traditional use of Z. montanum rhizomes for the treatment of cancer.

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Zhu, Yanqin, Qinhong Yin, and Yaling Yang. "A comparative study of HPLC-DAD and UPLC-UV methods for simultaneous determination of 11 polyphenols in Moringa oleifera leaves." Tropical Journal of Pharmaceutical Research 20, no. 11 (December 13, 2021): 2371–79. http://dx.doi.org/10.4314/tjpr.v20i11.20.

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Purpose: To develop, validate and compare two chromatographic methods - high performance liquid chromatography with diode array detector ((HPLC-DAD) and high performance liquid chromatography with ultraviolet detection (UPLC-UV) for the effective analysis of polyphenols in Moringa oleifera leaves.Methods: HPLC-DAD and UPLC-UV methods were applied for the accurate determination of eleven major polyphenols in Moringa oleifera leaves. The chromatographic conditions of the eleven polyphenols was determined on two C18 column by gradient elution with 0.5 % phosphoric acid solution -acetonitrile as the eluate, and at a flow rate of 1.0 and 0.5 mL/min for HPLC-DAD and UPLC-UV methods, respectively. Detector parameter of UPLC-UV was fixed at 203 nm. The assay methods were validated systematically.Results: The instrumental methods (HPLC-DAD and UPLC-UV) had good linearity, precision,repeatability and recovery. For both methods, quantification limits of UPLC-UV (0.057 - 0.363 μg/mL) were lower than those of UPLC-UV (0.094 - 1.532 μg/mL). The UPLC method with a shorter running time and more sensitive detection was applied in comparing to the HPLC method. After optimization and evaluation, the baseline of 11 compounds was separated effectively within 68 and 34 min, respectively.Conclusion: The developed HPLC-DAD and UPLC-UV assays were successfully utilized for thesimultaneous analysis of eleven major polyphenols and can readily be utilized as quality control tools for Moringa oleifera leaves in China, with UPLC-UV method showing better separation, lower organic solvent usage and shorter analytical period.

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Cendejas-Bueno, Emilio, Manuel Cuenca-Estrella, and Alicia Gomez-Lopez. "Determination of Voriconazole Serum Concentration by Bioassay, a Valid Method for Therapeutic Drug Monitoring for Clinical Laboratories." Antimicrobial Agents and Chemotherapy 57, no. 7 (May 6, 2013): 3437–40. http://dx.doi.org/10.1128/aac.00323-13.

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ABSTRACTWe describe here a simple, fast, and reliable bioassay method for therapeutic drug monitoring of voriconazole. Fifty-eight clinical and external quality control samples were evaluated with this microbiological assay, and results were compared with those obtained with a previously validated chromatographic method. A good correlation between both assays was observed. This particular microbiological method was demonstrated to be simple and offers enough precision and accuracy to perform voriconazole therapeutic drug monitoring in laboratories without specialized equipment.

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Cunliffe, C. J., T. J. Franklin, and R. M. Gaskell. "Assay of prolyl 4-hydroxylase by the chromatographic determination of [14C]succinic acid on ion-exchange minicolumns." Biochemical Journal 240, no. 2 (December 1, 1986): 617–19. http://dx.doi.org/10.1042/bj2400617.

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An assay for prolyl 4-hydroxylase (EC 1.14.11.2) is described which measures succinic acid produced during the decarboxylation of 2-oxoglutaric acid in the presence of poly(L-Pro-Gly-L-Pro). [1-14C]Succinic acid was separated from its precursor 2-oxo[5-14C]glutaric acid by using ion-exchange minicolumns. The contamination of succinic acid by 2-oxoglutaric acid was approx. 1%, and the recovery of succinic acid was 100%. Kinetic parameters of prolyl 4-hydroxylase measured by the assay showed good agreement with published values. Our experience indicates that the measurement of prolyl 4-hydroxylase by the production of succinic acid is especially suited to investigations involving large numbers of assays.

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Fuqua, J. S., E. S. Sher, C. J. Migeon, and G. D. Berkovitz. "Assay of plasma testosterone during the first six months of life: importance of chromatographic purification of steroids." Clinical Chemistry 41, no. 8 (August 1, 1995): 1146–49. http://dx.doi.org/10.1093/clinchem/41.8.1146.

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Abstract Determination of the plasma concentration of testosterone (T) is important in evaluating infants born with ambiguous genitalia and micropenis, and several commercially available kits provide a direct assay of T in unextracted plasma. Using plasma samples obtained from 36 subjects < 6 months old, we compared the concentration of plasma T measured by RIA after extraction and purification by column chromatography with the T concentration measured in a direct assay. When aliquots of samples were purified before RIA, the concentration of T was markedly lower than in the direct assay. In the first 3 weeks postpartum, results of the direct assay were 3.8-fold greater than those obtained after purification. This difference decreased over time, and by age 2 months there was fairly good agreement between the two methods. These data indicate that some direct assays of plasma T are inappropriate during the first 2 months postpartum.

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Rouhiainen, Ari, Niko-Petteri Nykänen, Juha Kuja-Panula, Päivi Vanttola, Henri Huttunen, and Heikki Rauvala. "Inhibition of Homophilic Interactions and Ligand Binding of the Receptor for Advanced Glycation End Products by Heparin and Heparin-Related Carbohydrate Structures." Medicines 5, no. 3 (July 30, 2018): 79. http://dx.doi.org/10.3390/medicines5030079.

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Background: Heparin and heparin-related sulphated carbohydrates inhibit ligand binding of the receptor for advanced glycation end products (RAGE). Here, we have studied the ability of heparin to inhibit homophilic interactions of RAGE in living cells and studied how heparin related structures interfere with RAGE–ligand interactions. Methods: Homophilic interactions of RAGE were studied with bead aggregation and living cell protein-fragment complementation assays. Ligand binding was analyzed with microwell binding and chromatographic assays. Cell surface advanced glycation end product binding to RAGE was studied using PC3 cell adhesion assay. Results: Homophilic binding of RAGE was mediated by V1- and modulated by C2-domain in bead aggregation assay. Dimerisation of RAGE on the living cell surface was inhibited by heparin. Sulphated K5 carbohydrate fragments inhibited RAGE binding to amyloid β-peptide and HMGB1. The inhibition was dependent on the level of sulfation and the length of the carbohydrate backbone. α-d-Glucopyranosiduronic acid (glycyrrhizin) inhibited RAGE binding to advanced glycation end products in PC3 cell adhesion and protein binding assays. Further, glycyrrhizin inhibited HMGB1 and HMGB1 A-box binding to heparin. Conclusions: Our results show that K5 polysaccharides and glycyrrhizin are promising candidates for RAGE targeting drug development.

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Pawar, Vijaykumar, and Harinath More. "HPLC Method Validation for Quantification of Lisinopril." INTERNATIONAL JOURNAL OF PHARMACEUTICAL QUALITY ASSURANCE 14, no. 02 (June 25, 2023): 298–302. http://dx.doi.org/10.25258/ijpqa.14.2.10.

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This study aimed to develop a straightforward, sensitive, exact, quick, and accurate reverse phase high performance liquid chromatography (RP-HPLC) method for figuring out how much lisinopril is in pharmaceutical gels and other large amounts of medication. Agilent Zorbax Bonus-RP column (250 x 4.6 mm, 5μ) was used for the chromatographic separation. “A mobile phase composed of methanol and trifluoroacetic acid (50:50 v/v) was used to develop the analytical procedure. The flow was found to be occurring at a rate of 1-mL/min and with a wavelength of 215 nm. The retention time was 2.28 min. In a concentration range from 3–7 μg/mL (r2=0.998), the drug’s response was determined to be linear. The LoQ was 1.11 μg/mL, while the LoD was 0.36 μg/mL. Lisinopril’s %assay was determined to be 98.22%, while assays for the other medicines in the commercial formulation showed no interference from the excipients. This method functions well and can be applied to routine analysis.

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Journal articles on the topic 'Chromatographic assays'

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