Simultaneous on-line extraction and analysis of sirolimus (rapamycin) and ciclosporin in blood by liquid chromatography electrospray mass spectrometry

We developed a sensitive and specific semi-automated liquid chromatography- electrospray mass spectrometric (HPLC-ESI-MS) assay for the simultaneous qu antification of sirolimus and ciclosporin in blood. Following a simple prot ein precipitation step, the supernatants were injected into the HPLC system and extracted on-line. After column switching, the analytes were backflush ed from the extraction column onto the analytical narrow-bore column and el uted into the ESI-MS system. The assay was linear from 0.4 to 100 mu g/l si rolimus and from 2 to 1500 mu g/l ciclosporin. The mean recoveries of sirol imus and ciclosporin were 98 and 96%, respectively. The mean interday preci sion/accuracy was 8.6%/-4.8% for sirolimus and 9.3%/-2.9% for ciclosporin. (C) 1999 Elsevier Science B.V. All rights reserved.