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Evaluating Phthalate Contaminant Migration Using Thermal Desorption?Gas Chromatography?Mass Spectrometry (TD?GC?MS).

ABSTRACT: This study describes a methodology for evaluating regulatory levels of phthalate contamination. By collecting experimental data on short-term phthalate migration using thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS), the migration of di(2-ethylhexyl) phthalate (DEHP) from polyvinyl chloride (PVC) to polyethylene (PE) was found to be expressed by the Fickian approximation model, which was originally proposed for solid (PVC)/liquid (solvent) migration of phthalates. Consequently, good data correlation was obtained using the Fickian approximation model with a diffusion coefficient of 4.2 × 10^-12 cm²/s for solid (PVC)/ solid (PE) migration of DEHP at 25 °C. Results showed that temporary contact with plasticized polymers under a normal, foreseeable condition may not pose an immediate risk of being contaminated by phthalates at regulatory levels. However, as phthalates are small organic molecules designed to be dispersed in a variety of polymers as plasticizers at a high compounding ratio, the risk of migration-related contamination can be high in comparison with other additives, especially under high temperatures. With these considerations in mind, the methodology for examining regulatory levels of phthalate contamination using TD-GC-MS has been successfully demonstrated from the viewpoint of its applicability to solid (PVC)/solid (PE) migration of phthalates.

SUBMITTER: Ouchi Y

PROVIDER: S-EPMC6523191 | biostudies-literature | 2019 Apr

REPOSITORIES: biostudies-literature

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Project description:BackgroundMeasuring concentrations of metabolites of estradiol and progesterone in urine, instead of measuring serum concentrations, is common in research and also is used in patient care. The primary aim of this study was to demonstrate that analysis of urine samples dried on filter paper by gas chromatography with tandem mass spectrometry (GC-MS/MS) provides results similar to serum analyzed by radioimmunoassay (RIA). Secondary aims were to show that collection of four samples during the day (4-spot method) can be substituted for a 24-h collection, and that analysis of urine from dried samples is equivalent to liquid urine samples.MethodsThis prospective observational study compared results of urine and serum analyses. Urine samples from women throughout the menstrual cycle and single samples from postmenopausal women were evaluated. Urine was collected onto filter paper and dried. Dried urine was extracted, hydrolyzed, and derivatized prior to analysis by GC-MS/MS. Hormone concentrations were normalized to creatinine. Single samples were used to compare results of 24-h urine collection to the 4-spot method from a separate population of women and men. A subset of these samples were used to compare results from dried urine to liquid urine.ResultsThe primary study showed good reliability in the comparisons between the dried urine and serum assays. During the menstrual cycles of a subset of four women, urine metabolite concentrations followed the same pattern as serum concentrations. Comparison of 4-spot to 24-h urine collections and of dried to liquid urine measurements had intraclass correlation coefficients (ICC) greater than 0.95, indicating excellent agreement.ConclusionsFor estradiol and progesterone, the dried urine assay is a good surrogate for serum testing. The 4-spot method can be used instead of 24-h urine collections and dried urine results are comparable to liquid urine. The dried urine assay is useful for some clinical assessments of hormone disorders and may be useful in large epidemiologic studies due to ease of sample handling.

Project description:It has become increasingly important to qualitatively and quantitatively assess the volatile metabolites in a range of bodily fluids for use in monitoring health. There has been relatively little work on the quantitative analysis of compounds, particularly with respect to the effects of ethnicity or geographic location. A novel method for the quantification of compounds in stool using 13C labelled compounds as internal standards is presented. Using thermal desorption gas chromatography mass spectrometry, stool samples from 38 healthy volunteers were analysed. The 13C labelled compounds, acetone, ethyl butanoate, ethanoic acid, butanoic acid, 3-methylbutanoic acid, and indole, were added as internal standards. This process mimics the solubility characteristics of the compounds and thus the method was able to quantify the compounds within the solid stool. In total, 15 compounds were quantified: Dimethyl sulphide (26⁻25,626 ng/g), acetone (442⁻3006 ng/g), ethyl butanoate (39⁻2468 ng/g), ethyl 2-methylbutanoate (0.3⁻180 ng/g), dimethyl disulphide (35⁻1303 ng/g), 1-octen-3-one (12 ng/g), dimethyl trisulphide (10⁻410 ng/g), 1-octen-3-ol (0.4⁻58 ng/g), ethanoic acid (672⁻12,963 ng/g), butanoic acid (2493⁻11,553 ng/g), 3-methylbutanoic acid (64⁻8262 ng/g), pentanoic acid (88⁻21,886 ng/g), indole (290⁻5477 ng/g), and 3-methyl indole (37⁻3483 ng/g). Moreover, by altering the pH of the stool to pH 13 in conjunction with the addition of 13C trimethylamine, the method was successful in detecting and quantifying trimethylamine for the first time in stool samples (range 40⁻5312 ng/g). Statistical analysis revealed that samples from U.K. origin had five significantly different compounds (ethyl butanoate, 1-octen-3-ol, ethanoic acid, butanoic acid, pentanoic acid, and indole) from those of South American origin. However, there were no significant differences between vegetarian and omnivore samples. These findings are supported by pre-existing literature evidence. Moreover, we have tentatively identified 12 compounds previously not reported as having been found in stool.

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Evaluating Phthalate Contaminant Migration Using Thermal Desorption?Gas Chromatography?Mass Spectrometry (TD?GC?MS).

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