USE OF PARTICLE-LOADED MEMBRANES TO EXTRACT STEROIDS FOR HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHIC ANALYSES IMPROVED ANALYTE STABILITY AND DETECTION

Cortisol, cortisone, corticosterone, prednisone and prednisolone are extracted from serum using the novel particle-loaded octyl (C-8)-bonded silica in PTFE membrane. Extracts are directly injected, without further concentration, onto a narrow (2.0 mm) or conventional (4.6 mm) bore octyldecyl (C-18) HPLC column. Method performance data demonstrate linearity from 0.4 mu g/dl (low limit of detection) up to at least 60 mu g/dl. Extraction recoveries exceeded 85% and precision (between-run) R.S.D.s averaged <5%. Interferences were minimal and selectivity was improved over conventional immunochemical steroid assays. When compared to large particle sorbents packed in columns or to traditional liquid-liquid extractions, the membrane extracted steroids in less time, used less reagent, and had smaller elution volumes, thereby obviating steroid instability/adsorption problems associated with traditional concentrating techniques required to improve analytical sensitivity.