Ultra fast liquid chromatography-tandem mass spectrometry routine method for simultaneous determination of cyclosporin A, tacrolimus, sirolimus, and everolimus in whole blood using deuterated internal standards for cyclosporin A and everolimus.

Specific chromatographic methods for the measurement of cyclosporin A, tacrolimus, sirolimus, and everolimus blood levels in patients with organ transplants are time consuming when large numbers of samples must be processed. The authors developed a robust and fast (1 minute) online solid-phase extraction liquid chromatography/tandem mass spectrometry method for the simultaneous quantification of cyclosporin A, tacrolimus, sirolimus, and everolimus. After protein precipitation of the whole blood with zinc sulphate and methanol, the supernatant was loaded on a wide pore reversed-phase column and cleansed of potential interferences with high flow for 20 seconds. After column switching, the analytes were transferred within 20 seconds in the back-flush mode to a short phenyl-hexyl column. The valve was then returned to its initial position and the chromatographic separation performed within 20 seconds. In the meantime, the loading column was prepared for the next injection. Ammoniated adducts of protonated molecules were used as precursor ions for all analytes. Multiple-reaction mode transitions for each immunosuppressant and the internal standards were used for quantification. The working range of the method was 10-1500 microg/L for cyclosporin A, 1.0-44 microg/L for tacrolimus, 1.0-48 microg/L for sirolimus, and 1.2-48 microg/L for everolimus. Within and between-run assay coefficients of variation ranged from 1.8% to 13.0%. The described liquid chromatography/tandem mass spectrometry method shows best performance using the internal standards cyclosporin A-d4 for cyclosporin A, everolimus-d4 for everolimus and ascomycin for tacrolimus and sirolimus. In conclusion, the authors present a very fast, robust, and economical analytical method for therapeutic monitoring of multiple immunosuppressants in daily clinical practice.