Use of Sep-pak cartridges for urinary steroid extraction: evaluation of the method for use prior to gas chromatographic analysis.

A method is described for the rapid and quantitative extraction of free and conjugated steroids from urine using Sep-pak C18 cartridges. The method was evaluated by determining the efficiency of recovery of (1) radiolabeled steroid glucuronides, (2) radiolabeled steroids freed by enzymatic hydrolysis, (3) steroid sulphates, (4) selected reference neutral free steroids of varied structure and polarity, and (5) oestrogens. In all cases the cartridges gave results equal to or better than those obtained by solvent or Amberlite XAD-2 extraction methods. Each urine extraction could be completed in 2-3 minutes and no further purification of extracts was required prior to derivatisation and gas chromatographic analysis.