Simultaneous Liquid-Chromatographic Determination of Prednisone and Prednisolone in Plasma

This high-performance liquid-chromatographic (HPLC) meth-od for simultaneous determination of prednisone and its metabolite, prednisolone, in plasma is a modification of the method of Frey et al. (Clin Chem 1979;25:1944-7). Heparin-ized plasma (1.0 mL) with 0.1 mL of internal standard solution (1 1-deoxy-1 7-hydroxycorticosterone, 2 mg/L) is ex-tracted with 7.0 mL of dichioromethane, then washed Se-quentially with 0.1 mol/L HCI, 0.1 mol/L NaOH, and de-ionized water, 2.0 mL each. The extract is evaporated and the residue reconstituted with 75 p.L of mobile phase, meth-anol/H20 (40/60 by vol). Thirty microliters of this is injected onto a reversed-phase C6 column, which is eluted at 1.4 mLlmin. Analytical recoveries of prednisone and predniso-lone were 94-98 % and 1 02-1 06%, respectively. Day-to-day precision (CV) was 3.8 % for prednisone, 6. 1 % for predniso