A simple liquid–liquid extraction with hexane for low-picogram determination of drugs and their metabolites in plasma by high-performance liquid chromatography with positive ion electrospray tandem mass spectrometry

✍ Scribed by Yuan-Qing Xia; Daisy B. Whigan; Mohammed Jemal

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 246 KB
• Volume: 13
• Category: Article
• ISSN: 0951-4198
• DOI: 10.1002/(sici)1097-0231(19990815)13:15<1611::aid-rcm683>3.0.co;2-c

✦ Synopsis

Four sensitive, specific and accurate methods, based on high-performance liquid chromatography (HPLC) with positive ion electrospray tandem mass spectrometry (MS/MS) coupled with liquid-liquid extraction (LLE), have been developed and validated for the low-picogram determination of two drug candidates and a metabolite (compounds I-III) in human, monkey and rat plasma. In the LLE procedure, hexane or a mixture of hexane and methyl t-butyl ether was used to isolate these compounds from plasma of the different species after basification of each biological sample with sodium carbonate. The reconstituted extracts were then injected into a positive ion electrospray LC/MS/MS system for the quantitative analysis. The lower limit of quantitation of the methods ranged from 20 to 200 pg/mL. The use of hexane for the LLE proved to be simple, rapid and reproducible, and provided very clean extracts with little interference. The inter-and intra-day precision for the four methods was within 9%, and the accuracy was in the range 94-107%. The effect of pH on the isomerization of I (E-isomer) to its Z-isomer (II) showed that the rate of isomerization increased with decrease in pH and that there was no isomerization at pH !6.