ABSTRACT
Probe electrospray ionization (PESI) is one of the typical types of ambient ionization technology, but its application in quantitative analysis is limited due to its poor sampling stability. Previously, we developed a new micro-pen electrospray ionization tandem mass spectrometry (μPen-ESI-MS/MS) method based on PESI. In this study, a μPen-ESI-MS/MS method to measure testosterone and dextromethorphan in liver microsome samples was developed and validated to further applicate in evaluating drug metabolism stability and CYP450 enzyme activity. A μPen-ESI-MS/MS method for detecting the CYP3A4 substrate testosterone and CYP2D6 substrate dextromethorphan in the liver microsome incubation system were developed, and the linearity, precision and accuracy of the method was validated. The validated method was further used to detect the metabolic stability of testosterone in the liver microsome incubation system. The results showed that the μPen-ESI-MS/MS had high efficiency with 0.3 min spraying time of each sample. The standard curve of the testosterone and dextromethorphan has good linearity (R2 > 0.99), the intra- and inter-batch accuracy of testosterone and dextromethorphan was 95.9%-109.3% and 90.5%-107.3%, respectively; the intra- and inter-batch precision was acceptable with RSD values of 2.4%-13.5% and 3.4%-12.1%. The half-lives of testosterone and dextromethorphan in the liver microsome incubation system were 12 min and 14 min, respectively. This study provided a rapid and sensitive μPen-ESI-MS/MS method for the assay of testosterone and dextromethorphan in liver microsome samples, and provided a new strategy for the evaluation of drug metabolism stability and CYP3A4/CYP2D6 activity.
ABSTRACT
In this study, hollow fiber membrane extraction combined with ambient ionization mass spectrometry ( AMS) was developed for the simultaneous determination of 7 perfluorinated compounds ( PFCs) in aqueous solution, including perfluoroheptanoic acid ( PFHpA ) , perfluorooctanoic acid ( PFOA ) , perfluorooctane sulfonate acid ( PFOS ) , perfluorononanoic acid ( PFNA ) , perfluorodecanoic acid ( PFDA ) , perfluoroundecanoic acid ( PFUdA) , and perfluorododecanoic acid ( PFDoA) . PFCs were detected in negative ion mode using selective reaction monitoring ( SRM) mode. The extraction time and the pH value of extraction solution were optimized. 13 C4-PFOS and 13 C4-PFOA were used as internal standards for quantitative analysis. The method showed good linearity with correlation coefficient values ( r2 ) greater than 0. 991 for the seven target PFCs. With the exception of PFHpA, the limit of detection ( LOD) for other six PFCs was within ranges from 0. 8 to 2. 7 ng/L while the limit of quantitative (LOQ) was from 2. 7 ng/L to 8. 9 ng/L. The enrichment factor of five PFCs was more than two hundred. The developed method was applied to detect the seven PFCs in tap water and Pearl River water, and they were all not detected. The recoveries were within the ranges of 88. 5%-108. 3% and 94. 2%-116. 7% when 40 ng/L and 400 ng/L PFCs were spiked into tap water, respectively. In terms of the Pearl River water, the recoveries were within the ranges of 75. 0%-102. 6% and 81. 2%-97. 6% when 40 ng/L and 400 ng/L PFCs were spiked, respectively.