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Composition Characterization of Fatty Acid Zinc Salts by Chromatographic and NMR Spectroscopic Analyses on Their Fatty Acid Methyl Esters.

ABSTRACT: To implement EU REACH- (Registration, Evaluation, and Authorization of Chemicals-) like chemical legislations in various countries of which the purpose is human and environment safety, the first step is substance identification followed by the hazard and risk assessments. Although both structural and composition identifications are required, the latter can more importantly result in the essential data to fill out the required substance information such as purity and concentrations of constituents, as well as impurities. With fatty acid zinc salts (FAZSs) as an exemplary industrial chemical of which chromatographic and nuclear magnetic resonance (NMR) analyses were impossible due to their insolubility in water and any organic solvents, the composition characterization was tried by preparing their fatty acid methyl esters (FAMEs) using the conc. HCl/methanol/toluene method. This acid-catalyzed methyl esterification was optimized with zinc stearate as a surrogate substance. Gas chromatography-mass spectrometry (GC-MS) and NMR analyses on methyl-esterified products revealed that the optimum conditions were at 90°C for 10?min or 45°C for 30?min with two equivalent HCl as well as at 45°C for 10?min with five equivalent HCl. Almost all zinc stearates were converted into the corresponding fatty acids with 97-99% conversion rates. Free fatty acids (FFAs) were detected in extracted ion chromatograms of pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) in the methyl-esterified products with incomplete conversions of 73?79%. The optimized conc. HCl/methanol/toluene method of direct one-step reaction from FAZSs was compared with the two-step NaOH saponification/BF3-methanol method after acidic hydrolysis of FAZSs. The mechanism of fatty acid zinc salts into free fatty acids and fatty acid methyl esters was suggested with the evidence of the formation of Zn(OH)2.

SUBMITTER: Park KS

PROVIDER: S-EPMC6942835 | biostudies-literature | 2019

REPOSITORIES: biostudies-literature

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Composition Characterization of Fatty Acid Zinc Salts by Chromatographic and NMR Spectroscopic Analyses on Their Fatty Acid Methyl Esters.

Park Kwang Seo KS Kim Yun Ju YJ Choe Eun Kyung EK

Journal of analytical methods in chemistry 20191223

To implement EU REACH- (Registration, Evaluation, and Authorization of Chemicals-) like chemical legislations in various countries of which the purpose is human and environment safety, the first step is substance identification followed by the hazard and risk assessments. Although both structural and composition identifications are required, the latter can more importantly result in the essential data to fill out the required substance information such as purity and concentrations of constituent ...[more]

PMID: 31929937

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Project description:Nonalcoholic fatty liver disease (NAFLD) is a growing health problem, and a major challenge in NAFLD management is identifying which patients are at risk of progression to more serious disease. Simple measurements of liver fat content are not strong predictors of clinical outcome, but biomarkers related to fatty acid composition (ie, saturated vs. unsaturated fat) may be more effective. MR spectroscopic imaging (MRSI) methods allow spatially resolved, whole-liver measurements of chemical composition but are traditionally limited by slow acquisition times. In this work we present an accelerated MRSI acquisition based on spin echo single point imaging (SE-SPI), which, using appropriate sampling and compressed sensing reconstruction, allows free-breathing acquisition in a mouse model of fatty liver disease. After validating the technique's performance in oil/water phantoms, we imaged mice that had received a normal diet or a methionine and choline deficient (MCD) diet, some of which also received supplemental injections of iron to mimic hepatic iron overload. SE-SPI was more resistant to the line-broadening effects of iron than single-voxel spectroscopy measurements, and was consistently able to measure the amplitudes of low-intensity spectral peaks that are important to characterizing fatty acid composition. In particular, in the mice receiving the MCD diet, SE-SPI showed a significant decrease in a metric associated with unsaturated fat, which is consistent with the literature. This or other related metrics may therefore offer more a specific biomarker of liver health than fat content alone. This preclinical study is an important precursor to clinical testing of the proposed method. MR-based quantification of fatty acid composition may allow for improved characterization of non-alcoholic fatty liver disease. A spectroscopic imaging method with appropriate sampling strategy allows whole-liver mapping of fat composition metrics in a free-breathing mouse model. Changes in metrics like the surrogate unsaturation index (UIs) are visible in mice receiving a diet which induces fat accumulation in the liver, as compared to a normal diet; such metrics may prove useful in future clinical studies of liver disease.

Dataset Information

Composition Characterization of Fatty Acid Zinc Salts by Chromatographic and NMR Spectroscopic Analyses on Their Fatty Acid Methyl Esters.

Publications

Composition Characterization of Fatty Acid Zinc Salts by Chromatographic and NMR Spectroscopic Analyses on Their Fatty Acid Methyl Esters.

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