Solid-PhaseExtractionand LiquidChromatographyfor ImprovedAssayof Cyclosporinein Whole Bloodor Plasma

In this simple, precise, accurate, and specificisocraticliquid chromatographicprocedurefordeterminingcyclosporine,the cyclosporine is extracted from 1 mL of whole blood or from plasma, with 500 of cyclosponn D added per liter as internal standard, by elution from a Bond-Elut’ ” C18 extrac-tion column with 300 L of a mixtureof ethanol and tetrahy-drofuran. A 10O-L aliquot of the eluate, injected onto a cyano-phase analytical column, is eluted with a mixture of acetonitrile and pH 7.0 phosphate buffer at a flow rate of 1.0 mL/min and at 50 #{176}C.Detection is at 210 nm. The chromatog-raphy is complete in <14.0 mm. The method can measure <10.0 &g/L. Analytical recovery of cyclosporine added to whole blood ranged from 99 to 109 % for concentrationsup to 2000 pg/L. Between-runCVs ranged from 6.4 to 6.6%. None of numerousdrugsand steroidstested interfered.Resultsb