Automated, fast and sensitive quantification of drugs in blood by liquid chromatography-mass spectrometry with on-line extraction: immunosuppressants

We developed a universal LC-mass spectrometry assay with automated online e xtraction (LC/LC-MS) to quantify the immunosuppressants cyclosporine, tacro limus, sirolimus and SDZ-RAD alone or in combination in whole blood. After protein precipitation. samples were loaded on a C-18 extraction column, wer e washed and, after activation of the column-switching valve, were backflus hed onto the C-8 analytical column. [M+Na](+) ions were detected in the sel ected ion mode. For tacrolimus, sirolimus and SDZ-RAD, the assay was linear from 0.25 to 100 mug/l and for cyclosporine from 7.5 to 1250 mug/l (all (r )2>0.99). Analytical recovery was >85% and, in general, inter-day, intra-da y variability for precision and accuracy were <10%. (C) 2000 Elsevier Scien ce B.V. All rights reserved.