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Journal articles on the topic 'Aqueous phase ethylation'

Author: Grafiati

Published: 4 June 2021

Last updated: 19 February 2022

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1

Bowles, Karl C., and Simon C. Apte. "Determination of methylmercury in sediments by steam distillation/aqueous-phase ethylation and atomic fluorescence spectrometry." Analytica Chimica Acta 419, no. 2 (September 2000): 145–51. http://dx.doi.org/10.1016/s0003-2670(00)00997-1.

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2

Michel, Pierre, and Bernard Averty. "Tributyltin analysis in seawater by GC FPD after direct aqueous-phase ethylation using sodium tetrathylborate." Applied Organometallic Chemistry 5, no. 5 (September 1991): 393–97. http://dx.doi.org/10.1002/aoc.590050505.

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3

Bowles, Karl C., Simon C. Apte, and Leigh T. Hales. "Determination of butyltin species in natural waters using aqueous phase ethylation and off-line room temperature trapping." Analytica Chimica Acta 477, no. 1 (January 2003): 103–11. http://dx.doi.org/10.1016/s0003-2670(02)01397-1.

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4

Liang, L., M. Horvat, and N. S. Bloom. "An improved speciation method for mercury by GC/CVAFS after aqueous phase ethylation and room temperature precollection." Talanta 41, no. 3 (March 1994): 371–79. http://dx.doi.org/10.1016/0039-9140(94)80141-x.

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5

Swan, H. B. "Aqueous Phase Ethylation Atomic Emission Spectroscopy for the Determination of Methylmercury in Fish Using Permeated Dimethylmercury Calibration." Bulletin of Environmental Contamination and Toxicology 60, no. 4 (April 1, 1998): 511–18. http://dx.doi.org/10.1007/s001289900655.

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6

Leermakers, M., H. L. Nguyen, B. Vanneste, S. Galletti, W. Baeyens, and S. Kurunczi. "Determination of methylmercury in environmental samples using static headspace gas chromatography and atomic fluorescence detection after aqueous phase ethylation." Analytical and Bioanalytical Chemistry 377, no. 2 (September 1, 2003): 327–33. http://dx.doi.org/10.1007/s00216-003-2116-6.

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7

Ritsema, R., T. de Smaele, L. Moens, A. S. de Jong, and O. F. X. Donard. "Determination of butyltins in harbour sediment and water by aqueous phase ethylation GC-ICP-MS and hydride generation GC-AAS." Environmental Pollution 99, no. 2 (1998): 271–77. http://dx.doi.org/10.1016/s0269-7491(97)00128-0.

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8

Trieu, An Quoc, Huy Phuong Tran, and Dong Van Nguyen. "Methods development for the determination of methyl mercury in sediment samples using gas chromatography with atomic fluorescence detection." Science and Technology Development Journal 16, no. 2 (June 30, 2013): 53–60. http://dx.doi.org/10.32508/stdj.v16i2.1452.

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An analytical method for methylmercury (MeHg) using gas chromatography with atomic fluorescence detection is studied. The instrumental system is made based on a old gas chromatograph interfaced with an atomic fluorescence detector which is specific to Hg, currently available in our lab. Operating parameters for the GC-AFS system are optimised and analytical performances of the system are verified by quality control chart for stability. MeHg in sediment is leached and extracted to dichloromethane (DCM) in the presence of nitric acid, potassium chloride and copper sulfate. DCM in the extract is purged and MeHg is back extracted to aqueous phase followed by ethylation with sodium tetraethylborate in acetate buffer pH 5.3 containing potassium oxalate. The ethylated MeHg is then extracted to hexane and injected to GC-AFS for quantitation. The instrumental detection limit and method detection limit are 0.5 pg MeHg and 0.029 ppb MeHg (as Hg), respectively. The method can be applied for the determination of MeHg in soil, sludge and sediment samples.

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9

Bloom, Nicolas. "Determination of Picogram Levels of Methylmercury by Aqueous Phase Ethylation, Followed by Cryogenic Gas Chromatography with Cold Vapour Atomic Fluorescence Detection." Canadian Journal of Fisheries and Aquatic Sciences 46, no. 7 (July 1, 1989): 1131–40. http://dx.doi.org/10.1139/f89-147.

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A technique is presented, which allows the rapid and precise determination of methylmercury in aqueous samples. The sample is first reacted with sodium tetraethylborate, to convert the nonvolatile monomethyl mercury to gaseous methylethylmercury. The volatile adduct is then purged from solution, and recollected on a graphitic carbon column at room temperature. The methylethylmercury is then thermally desorbed from the column, and analyzed by cryogenic gas chromatography with cold vapour atomic fluorescence detection. The method allows the simultaneous determination of labile Hg(II) species, through the formation of diethylmercury, and of dimethylmercury, which is not ethylated. The methylmercury detection limit is about 0.6 pg Hg, or 0.003 ng∙L−1 for a 200-mL sample. The technique has been successfully applied directly to a wide variety of freshwater samples and alkaline tissue digestates. Seawater is analyzed following a simple extraction step to separate the methylmercury from the interfering chloride matrix. Analyses of natural surface waters have shown methylmercury levels typically in the range of 0.02–0.10 ng∙L−1, with values as high as 0.64 ng∙L−1 in a polluted urban lake. Waters collected from the anoxic bottom waters of a stratified remote lake have shown methylmercury levels as high as 4 ng∙L−1 as Hg.

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10

ST. PIERRE, JAMIE, SEDAT BEIS, and ADRIAAN VAN HEININGEN. "Pyrolysis of hardwood soda-anthraquinone spent pulping liquor." October 2015 14, no. 10 (November 1, 2015): 639–48. http://dx.doi.org/10.32964/tj14.10.639.

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A lignin-rich feedstock, soda-anthraquinone spent pulping liquor, was pyrolyzed in a kiln reactor. The liquor was prepared from mixed northern hardwood chips at a liquor-to-wood ratio of 3.5 L/kg, 16% effective alkali, and an H-factor of 1000 h. The spent liquor was pyrolyzed at 500°C as is, after oxygen oxidation, and with addition of sodium formate to determine the effect on bio-oil yield and product distribution. Contrary to bio-oil from sawdust, a clear phase separation of the liquid product into an aqueous layer and a denser organic layer is obtained. The predominant products found in the organic layer collected after pyrolysis are phenols with varying degrees of methylation and ethylation. The organic yield appears to go through a maximum (32 wt% on spent liquor organics) at around 25 wt% formate added on spent liquor dry solids and subsequently decreases at greater charges. Oxidation of the spent liquor prior to pyrolysis appears to have a detrimental effect on the organic yield.

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11

Liang, L., N. S. Bloom, and M. Horvat. "Simultaneous determination of mercury speciation in biological materials by GC/CVAFS after ethylation and room-temperature precollection." Clinical Chemistry 40, no. 4 (April 1, 1994): 602–7. http://dx.doi.org/10.1093/clinchem/40.4.602.

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Abstract We developed a method for the simultaneous determination of monomethyl mercury (MMHg), inorganic mercury [Hg(II)], and total mercury (THg) in biological materials. A variety of biological materials can be digested in methanolic KOH solution. The MMHg and Hg(II) present are converted to volatile ethyl derivatives, methylethyl mercury and diethyl mercury, by an aqueous-phase ethylation reaction with sodium tetraethylborate. The ethyl derivatives are precollected onto a trapping column at room temperature, in case of disconnection with the separation/detection system, and then thermally desorbed into a packed isothermal gas chromatography (GC) column. Eluted organo-Hg compounds from the GC column are decomposed into Hg0, and detection is completed by cold vapor atomic fluorescence spectrometry (CVAFS). Pure standard solutions can be used for calibration. The sum of MMHg and Hg(II) obtained by this method equals the THg value obtained by digestion with HNO3 and H2SO4, reduction with SnCl2, and single-stage amalgamation/CVAFS for all biological materials studied. Absolute detection limits are 0.6 pg and 1.3 pg of Hg as MMHg and Hg(II), respectively, corresponding to 0.3 ng and 0.6 ng/g (wet) of sample.

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12

Kadlecova, Milada, Mirna Daye, and Baghdad Ouddane. "Improvement in Determination of Methylmercury in Sediments by Headspace Trap Gas Chromatography and Atomic Fluorescence Spectrometry after Organic Extraction and Aqueous Phase Ethylation." Analytical Letters 47, no. 4 (March 3, 2014): 697–706. http://dx.doi.org/10.1080/00032719.2013.848364.

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13

Cai, Y., and J. M. Bayona. "Simultaneous Speciation of Butyl-, Phenyl-, and Cyclohexyltin Compounds in Aqueous Matrices Using Ethylation Followed by Solid-Phase Trace Enrichment, SFE, and GC Determination." Journal of Chromatographic Science 33, no. 3 (March 1, 1995): 89–97. http://dx.doi.org/10.1093/chromsci/33.3.89.

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14

Bloom, Nicolas S. "On the Chemical Form of Mercury in Edible Fish and Marine Invertebrate Tissue." Canadian Journal of Fisheries and Aquatic Sciences 49, no. 5 (May 1, 1992): 1010–17. http://dx.doi.org/10.1139/f92-113.

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Total mercury, monomethylmercury (CH3Hg), and dimethylmercury ((CH3)2Hg) in edible muscle were examined in 229 samples, representing seven freshwater and eight saltwater fish species and several species of marine invertebrates using ultraclean techniques. Total mercury was determined by hot HNO3/H2SO4/BrClldigestion, SnCl2 reduction, purging onto gold, and analysis by cold vapor atomic fluorescence spectrometry (CVAFS). Methylmercury was determined by KOH/methanol digestion using aqueous phase ethylation, cryogenic gas chromatography, and CVAFS detection. Total mercury and CH3Hg concentrations varied from 0.011 to 2.78 μg∙g−1 (wet weight basis, as Hg) for all samples, while no sample contained detectable (CH3)2Hg (<0.001 μg∙g−1 as Hg). The observed proportion of total mercury (as CH3Hg) ranged from 69 to 132%, with a relative standard deviation for quintuplicate analysis of about 10%; nearly all of this variability can be explained by the analytical variability of total mercury and CH3Hg. Poorly homogenized samples showed greater variability, primarily because total mercury and CH3Hg were measured on separate aliquots, which vary in mercury concentration, not speciation. I conclude that for all species studied, virtually ail (>95%) of the mercury present is as CH3Hg and that past reports of substantially lower CH3Hg fractions may have been biased by analytical and homogeneity variability.

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15

Morrison, Kenneth A., and Carl J. Watras. "Mercury and methyl mercury in freshwater seston: direct determination at picogram per litre levels by dual filtration." Canadian Journal of Fisheries and Aquatic Sciences 56, no. 5 (May 1, 1999): 760–66. http://dx.doi.org/10.1139/f99-029.

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Here, we describe a method for directly determining sestonic mercury in lake waters at concentrations ranging down to 0.12 ng Hg/L (total Hg) and 0.01 ng MeHg/L (monomethyl mercury) in a 250-mL water sample. Detection limits for the method are 30 pg of Hg and 3.0 pg of MeHg, reported as three times the standard deviation of a procedural blank. The method involves dual filtration using ultraclean 47-mm-diameter, 0.45-µm pore size cellulose nitrate filters in an all-Teflon® filter stack. Lake water is pumped directly through a primary filter that traps suspended seston particles and then through a secondary filter that is used to estimate the integrated reagent, filter, and sorption blank. Both filters are analyzed for Hg or MeHg and the primary filter is corrected by subtracting the secondary blank. Sestonic Hg is determined after acid digestion and wet oxidation of the filters with BrCl, reduction with NH2OH-HCl followed by SnCl2, and purging via N2 onto dual gold traps for detection via cold-vapor atomic fluorescence spectroscopy. Sestonic MeHg is determined after acid distillation of the filters, aqueous-phase ethylation, purging onto Tenax®, isothermal gas chromatography separation, and detection by cold-vapor atomic fluorescence spectroscopy. The method was tested on a variety of lakes in Wisconsin, Florida, and Washington. The blank-corrected mass of sestonic mercury collected from these lakes onto primary filters ranged from 30 to 340 pg Hg and from 3 to 23 pg MeHg. The corresponding concentrations of mercury in the seston were 22-790 ng Hg/g dry weight and 3-75 ng MeHg/g dry weight. The method allowed us to demonstrate a clear negative dependence of sestonic mercury concentrations (weight:weight) on pH in Wisconsin lakes.

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