Semi-automated high-performance liquid chromatographic determination of cyclosporine A in whole blood using one-step sample purification and column-switching.

A highly sensitive and semi-automated high-performance liquid chromatographic method, utilizing acetonitrile protein precipitation and column-switching, is described for the determination of cyclosporine A in whole blood. Following a rapid manual acetonitrile treatment of the blood samples, the supernatant is loaded automatically onto a 5-micron high-speed protein separation column without any further clean-up operations. The fraction containing cyclosporine A is switched to a 3-micron C18 reversed-phase high-speed column by a microprocessor-controlled column-switching unit for final separation and detection by absorption at 214 nm. Minimal sample handling and efficient separation resulted in a high recovery (75 +/- 3%) of cyclosporine A from blood and a detection limit as low as 2 micrograms/l with a highly reproducible and linear response up to 2500 micrograms/1 using 0.5 ml of sample. A separation cycle including regeneration of the first column is finished in 15 min, and this system was used continuously for ca. 1000 blood samples from heart, liver, kidney, pancreas and bone marrow recipients without change in separation parameters or material replacement. The method described allows accurate and very fast daily routine monitoring of cyclosporine A in large numbers of blood samples from transplant recipients.