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Chromatographia - An LC-MS method is described for the determination of 4,4′-MDA (4,4′-methylene dianiline) in hydrolysed urine as a biomarker for exposure to 4,4′-MDI... 相似文献
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Trace analysis of airborne 1,6-hexamethylenediisocyanate and the related aminoisocyanate and diamine by glass capillary gas chromatography 总被引:1,自引:0,他引:1
A capillary gas chromatographic method was developed for the analysis of complex air mixtures of 1,6-hexamethylenediisocyanate, 1,6-hexamethyleneaminoisocyanate and 1,6-hexamethylenediamine. The method is based on derivatization in the sampling step of the reactive isocyanate groups to corresponding urethane groups by the alkaline ethanolic solvent and a subsequent derivatization of remaining amino groups to amide groups with heptafluorobutyric acid anhydride. The overall procedure, including sampling, gave a linear response at air concentrations of 3-300 micrograms/m3 for 1,6-hexamethylenediisocyanate with a precision of ca. 4% at 15 micrograms/m3 and a detection limit of ca. 0.2 microgram/m3 using nitrogen selective detection. In a field measurement of air concentrations in welding work on lacquered metal parts at a motor-car workshop, concentrations of 1,6-hexamethylenediisocyanate above 600 micrograms/m3 were found. Also 1,6-hexamethyleneaminoisocyanate and 1,6-hexamethylenediamine were found at concentrations of the order of 15% of the 1,6-hexamethylenediisocyanate concentration. 相似文献
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Daniel Karlsson Jakob Dahlin Åsa Marand Gunnar Skarping Marianne Dalene 《Analytica chimica acta》2005,534(2):263-269
A method for the determination of isocyanates as di-n-butyl amine (DBA) derivatives using tandem mass spectrometry (MS/MS) and electrospray ionisation (ESI) is presented. Multiple-reaction monitoring (MRM) of the protonated molecular ions and corresponding deuterium-labelled d9-DBA derivatives resulted in selective quantifications with correlation coefficients >0.998 for the DBA derivatives of isocyanic acid (ICA), methyl isocyanate (MIC), ethyl isocyanate (EIC), propyl isocyanate (PIC), phenyl isocyanate (PhI), 1,6-hexamethylene diisocyanate (HDI), 2,4-, 2,6-toluene diisocyanate (TDI), isophorone diisocyanate (IPDI), 4,4′-methylenediphenyl diisocyanate (MDI), 3-ring MDI, 4-ring MDI, HDI-isocyanurate, HDI-diisocyanurate, HDI-biuret and HDI-dibiuret. The instrumental precision for 10 repeated injections of a solution containing 0.1 μg ml−1 of the studied derivatives was <2%. Performing MRM of the product ion [DBA + H]+ (m/z = 130) from the protonated molecular ion resulted in the lowest detection limits, down to 10 amol (for TDI). Quantification of concentrations below 10−6 of the occupational exposure limit (OEL) for TDI during 10 min of air sampling was made possible. In an effort to control the formation of alkali adducts, addition of lithium acetate to the mobile phase and monitoring of lithium adducts was evaluated. Having lithium present in the mobile phase resulted in complete domination of [M + Li]+ adducts, but detection limits for the studied compounds were not improved. Different deuterium-labelled derivatives as internal standards were evaluated. (1) DBA derivatives of deuterium-labelled isocyanates (d4-HDI, d3-2,4-TDI, d3-2,6-TDI and d2-MDI), (2) d9-DBA derivatives of the corresponding isocyanates and (3) d18-DBA derivatives of the corresponding isocyanates. An increase in number of deuterium in the molecule of the internal standard resulted in an increase in instrumental precision and a decrease in correlation within calibration series. 相似文献
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Chantelle Human Dalene de Beer Magdalena Muller Marieta van der Rijst Marique Aucamp Andreas Tredoux Andr de Villiers Elizabeth Joubert 《Molecules (Basel, Switzerland)》2021,26(17)
Green rooibos extract (GRE), shown to improve hyperglycemia and HDL/LDL blood cholesterol, has potential as a nutraceutical beverage ingredient. The main bioactive compound of the extract is aspalathin, a C-glucosyl dihydrochalcone. The study aimed to determine the effect of common iced tea ingredients (citric acid, ascorbic acid, and xylitol) on the stability of GRE, microencapsulated with inulin for production of a powdered beverage. The stability of the powder mixtures stored in semi-permeable (5 months) and impermeable (12 months) single-serve packaging at 30 °C and 40 °C/65% relative humidity was assessed. More pronounced clumping and darkening of the powders, in combination with higher first order reaction rate constants for dihydrochalcone degradation, indicated the negative effect of higher storage temperature and an increase in moisture content when stored in the semi-permeable packaging. These changes were further increased by the addition of crystalline ingredients, especially citric acid monohydrate. The sensory profile of the powders (reconstituted to beverage strength iced tea solutions) changed with storage from a predominant green-vegetal aroma to a fruity-sweet aroma, especially when stored at 40 °C/65% RH in the semi-permeable packaging. The change in the sensory profile of the powder mixtures could be attributed to a decrease in volatile compounds such as 2-hexenal, (Z)-2-heptenal, (E)-2-octenal, (E)-2-nonenal, (E,Z)-2,6-nonadienal and (E)-2-decenal associated with “green-like” aromas, rather than an increase in fruity and sweet aroma-impact compounds. Green rooibos extract powders would require storage at temperatures ≤ 30 °C and protection against moisture uptake to be chemically and physically shelf-stable and maintain their sensory profiles. 相似文献
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Chromatographia - 1,6-Diaminohexane (DAH, 1,6-hexamethylene diamine) and isophorone diamine (IPDA) have been derivatized with trifluoroethyl chloroformate (TFECF) using a two-phase procedure.... 相似文献
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Dalene de Beer Gerold Jerz Elizabeth Joubert Victor Wray Peter Winterhalter 《Journal of chromatography. A》2009,1216(19):4282-4289
Isomangiferin was isolated from Cyclopia subternata using a multi-step process including extraction, liquid–liquid partitioning, high-speed counter-current chromatography (HSCCC) and semi-preparative reversed-phase high-performance liquid chromatography (HPLC). Enrichment of phenolic compounds in a methanol extract of C. subternata leaves was conducted using liquid–liquid partitioning with ethyl acetate–methanol–water (1:1:2, v/v). The enriched fraction was further fractionated using HSCCC with a ternary solvent system consisting of tert-butyl methyl ether–n-butanol–acetonitrile–water (3:1:1:5, v/v). Isomangiferin was isolated by semi-preparative reversed-phase HPLC from a fraction containing mostly mangiferin and isomangiferin. The chemical structure of isomangiferin was confirmed by LC–high-resolution electrospray ionization MS, as well as one- and two-dimensional NMR spectroscopy. 相似文献