Abstract:

Alcohol intake is an important risk factor for cardiovascular disease, liver disease, and diabetes. The accurate and objective evaluation of alcohol intake is important for disease prevention and intervention, as well as alcohol intake monitoring. Phosphatidylethanol (PEth) is a potential clinical biomarker of alcohol consumption. Monitoring PEth levels can provide an objective and quantitative basis for alcohol intake studies. Unlike other current alcohol biomarkers, PEth can only be produced in the presence of alcohol. Therefore, PEth is highly specific for alcohol intake and not affected by confounding factors, such as age, gender, hypertension, kidney disease, liver disease, and other comorbidities. Because of its long half-life and high specificity for alcohol intake, PEth may be used as a tool for monitoring drinking behavior in the clinical, transportation, and other fields. Given rapid developments in mass spectrometry technology over the past decade, liquid chromatography-tandem mass spectrometry (LC-MS/MS) has become the preferred method for PEth detection. However, most current LC-MS/MS methods focus on the determination of one or several PEth homologs, and the number of PEth homologs that can be determined simultaneously is relatively limited. Moreover, the detection capacity of the available methods remains insufficient, and their analytical sensitivity for some PEth homologs must be further improved. In this study, a novel LC-MS/MS method based on an intelligent scheduled time-zone negative multiple reaction monitoring acquisition technology (Scheduled-MRM) was developed. The technology monitors two ion channels in each PEth to ensure reliable results and can quantify 18 PEth homologs in human whole blood simultaneously. Methanol-methyl tert-butyl ether-water was used as the extraction system. An XBridge C18 column (100 mm×2.1 mm, 3.5 μm) was selected for gradient elution with 2.5 mmol/L ammonium acetate isopropanol solution and 2.5 mmol/L ammonium acetate aqueous solution-acetonitrile (50:50, v/v) as the mobile phases. Negative electronic spray ionization in scheduled-MRM mode was applied for MS/MS detection. The method was validated to have a linear range of 10-2500 ng/mL with correlation coefficients greater than 0.9999. The limits of detection and quantification were 0.7-2.8 and 2.2-9.4 ng/mL, respectively, and the spiked recoveries ranged from 91.0% to 102.2%. The method was confirmed to be simple, rapid, and precise, and subsequently validated for the measurement of 18 PEth homologs in human blood. Scheduled-MRM can assign a suitable scan time to each ion channel and effectively reduce the number of concurrent ion pairs monitored per unit time. This technology overcomes the problem of insufficient dwell time caused by an excessive number of ion channels, thereby avoiding the redundant monitoring of non-retention times. Scheduled-MRM significantly improved the detection sensitivity, data acquisition quality, and signal response of the proposed method. Whole blood samples from 359 volunteers with regular drinking habits were analyzed using this method. The total PEth concentrations ranged from 51.13 ng/mL to 2.89 μg/mL, with a mean of 363.16 ng/mL. PEth 16:0/18:1 and 16:0/18:2 were the two most abundant homologs, with mean concentrations of 74.21 and 48.75 ng/mL, accounting for approximately 20.43% and 13.42%, respectively, of the total PEth. Spearman correlation analyses showed that the PEth homologs correlated well with each other, γ-glutamyltransferase, a clinically available biological marker of alcohol, and other clinical biochemical parameters related to liver and kidney function. Overall, the method was demonstrated to be sensitive, precise, and accurate; thus, it may be an effective tool for monitoring alcohol intake in the clinical and other fields.

Key words: high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS), intelligent scheduled time-zone acquisition technology, phosphatidylethanol (PEth), alcohol intake monitoring