Direct injection versus liquid-liquid extraction for plasma sample analysis by high performance liquid chromatography with tandem mass spectrometry

✍ Scribed by Mohammed Jemal; Mike Huang; Xiaohui Jiang; Yan Mao; Mark L. Powell

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 131 KB
• Volume: 13
• Category: Article
• ISSN: 0951-4198
• DOI: 10.1002/(sici)1097-0231(19991115)13:21<2125::aid-rcm763>3.0.co;2-h

✦ Synopsis

Direct injection versus liquid-liquid extraction for post-dose human plasma sample analysis by high performance liquid chromatography with tandem mass spectrometry (LC/MS/MS) have been studied using a drug candidate compound. For the direct-injection method, an Oasis 1 HLB column (1 Â 50 mm, 30 mm) was used as the on-line extraction column and a conventional Waters symmetry C18 column (3.9 Â 50 mm, 5 mm) was used as the analytical column. Each plasma sample (100mL) was mixed with 100 mL of a working solution of the internal standard in aqueous 0.05 M ammonium acetate (pH 6.9), and portions (10 mL) of these samples were then injected into the LC/MS/MS system. For the liquid-liquid extraction method, a YMC Basic C18 column (2.0 Â 50 mm, 5 mm) was used as the analytical column. Each sample (0.5 mL) was extracted with methyl tert-butyl ether and the extract was reconstituted and injected into the LC/MS/MS system. The total analysis time for both methods was 2.0 min per sample. The accuracy, inter-day precision and intra-day precision obtained from the quality control samples were within 8% for both methods. The analysis results of post-dose human plasma samples showed that the deviations of 91% of the concentrations obtained using the direct-injection method were within AE20% from the concentrations obtained using the liquid-liquid extraction method, and the overall average percentage deviation was À1.5%. The results showed that the two methods were equivalent in terms of total chromatographic run time, accuracy and precision. However, for a batch of 100 samples, the sample preparation time for the direct-injection method was only about 25% of the time required for liquid-liquid extraction. This decrease in sample preparation time resulted in the doubling of the overall sample analysis throughput.