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Quantitation of simvastatin and its β‐hydroxy acid in human plasma by liquid–liquid cartridge extraction and liquid chromatography/tandem mass spectrometry
Author(s) -
Zhao Jamie J.,
Xie Iris H.,
Yang Amy Y.,
Roadcap Brad A.,
Rogers J. D.
Publication year - 2000
Publication title -
journal of mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 1076-5174
DOI - 10.1002/1096-9888(200009)35:9<1133::aid-jms42>3.0.co;2-x
Subject(s) - chemistry , chromatography , cartridge , analyte , extraction (chemistry) , tandem mass spectrometry , solid phase extraction , mass spectrometry , sample preparation , liquid chromatography–mass spectrometry , high performance liquid chromatography , mechanical engineering , engineering
A sensitive and reliable procedure for the simultaneous determination of simvastatin (SV) and its active β‐hydroxy acid metabolite (SVA) in human plasma was developed and validated. The analytes were extracted simultaneously from 0.5 ml aliquots of human plasma samples by methyl tert ‐butyl ether (MTBE) via Chem Elut cartridge extraction [also called liquid–solid extraction (LSE) or liquid–liquid cartridge extraction (LLCE)], separated through a Kromasil C 18 column (50 × 2 mm i.d. 5 µm) and detected by tandem mass spectrometry with a turbo ionspray interface. Stable isotope‐labeled SV and SVA, 13 CD 3 ‐SV and 13 CD 3 ‐SVA, were used as internal standards. SV and SVA were detected in positive and negative ion modes, respectively, via within‐run polarity switching. The use of Chem Elut cartridges not only provided a simple and efficient means of plasma sample extraction but also successfully reduced the interconversion between SV and SVA to an undetectable (for lactonization of SVA) or negligible (<0.07%, for hydrolysis of SV) level. The method showed excellent reproducibility, with intra‐ and inter‐assay precisions <4.5% (RSD), and intra‐ and inter‐assay accuracy between 94% and 107% of nominal values, for both analytes. The extraction recoveries were 78% and 87% on average for SV and SVA, respectively. The analyte was found to be stable in plasma through three freeze (−70 °C)–thaw (4 °C) cycles and for at least 3 h under bench‐top storage condition in an ice‐bath (4 °C), and also in the reconstitution solution at 4 °C for at least 24 h. The method has a lower limit of quantitation (LOQ) of 50 pg ml −1 with a linear calibration range of 0.05–50 ng ml −1 for both analytes, and has proved to be very reliable for the analysis of clinical samples. Copyright © 2000 John Wiley & Sons, Ltd.