Efficient determination of six fatty acid ethyl ethers in human whole blood by gas chromatography-mass spectrometry

Development of a simultaneous quantitation for short-, medium-, long-, and very long-chain fatty acids in human plasma by 2-nitrophenylhydrazine-derivatization and liquid chromatography-tandem mass spectrometry

Fatty acids (FA) have been important in clinical diagnosis for long, which makes the increasing need for a fast, reliable, and economic approach to determine FA of short-, medium-, long-, and very long-chain by widely available equipment and with high-throughput capacity. In the present work, 2‑nitrophenylhydrazine derivatization coupling with LC-MS/MS detection was utilized to simultaneously quantitate 18 FAs ranging from C4 to C26 in human plasma. The sample preparation protocol was optimized and extracting with diethyl ether‑potassium phosphate buffer twice was found as the highest efficiency along with economic feasibility. Under the optimized conditions, all the FA showed excellent linearity (R² > 0.999 for each), sufficient sensitivity (LOD 0.2-330 fmol and LOQ 2.3-660 fmol for all), favorable accuracy (recovery ranged from 98.1 ± 3.6% to 104.9 ± 5.5% with coefficient of variation no >8.6% for all), and negligible matrix effect. In the clinical application on 30 healthy subjects, compared with the previous HPLC-UV method, the developed method showed high reliability, as well as reduced time and reagent costs. The established method showed the potential to apply to not only diagnostic practice, but also nutritional and epidemiological studies.

Stability of Ethyl Glucuronide, Ethyl Sulfate, Phosphatidylethanols and Fatty Acid Ethyl Esters in Postmortem Human Blood

The lack of systematic studies on the stability of ethanol's non-oxidative metabolites in postmortem specimens restricts their use in forensic cases. This study aimed to compare the stability of ethyl glucuronide (EtG), ethyl sulfate (EtS), phosphatidylethanols (PEths) and fatty acid ethyl esters (FAEEs) in postmortem human blood. Three groups were established based on the level and source of ethanol: the blank group, the ethanol-spiked group and the ethanol-positive group. Each group contained six blood samples from different corpses. The samples in each group were placed at 37, 25, 4 and -20°C. Every 24 h for 7 days, 50 μL was collected from each sample. The levels of EtG, EtS, PEths and FAEEs were determined by liquid chromatography-mass spectrometry, and their stability was evaluated. EtG was not detected in the blank group, but it was found in samples in the ethanol-spiked group placed at 37°C, and it was degraded in the ethanol-positive group at 37 and 25°C. EtS showed no change in any of the groups. PEths were not detected in the blank group, but formation was found in the ethanol-spiked group at all temperatures. In the ethanol-positive group, PEth levels fluctuated at 37°C, decreased at 25°C and increased at -20°C. FAEEs were generated in the blank group and in the ethanol-spiked group at all temperatures. In the ethanol-positive group, FAEEs were degraded at 37 and 25°C but were generated at 4 and -20°C. EtS is a reliable biomarker of ethanol consumption, and EtG could be used as a biomarker at low temperatures (4 and -20°C), but PEths and FAEEs are not appropriate biomarkers of ethanol consumption.