Non-aqueous enzymatic flow injection determination of cholestanol in sediments

A procedure was developed for the spectrophotometric determination of cholestanol in sediments based on its extraction with chloroform-methanol (2 + 1 v/v), dissolution of the extracts, after preconcentration, in pH 7.0 buffer-saturated toluene containing 10(-3) M p-anisidine and enzymatic determination in non-aqueous media using a bienzymic reactor consisting of 1 mg of cholesterol oxidase and 1 mg of horseradish peroxidase non-covalently co-immobilized on controlled pore glass beads. A limit of detection of 2.0 x 10(-6) M was obtained under the optimum experimental conditions and recoveries of 95-118% were obtained in the analysis of water and beach sediment samples spiked with cholestanol at concentration levels of 0.4-1.0 mg g(-1). This method can also be employed for the determination of cholesterol in sediment extracts, the analytical sensitivity for cholestanol being half that for cholesterol, and studies were carried out in order to determine accurately both compounds in the same sample.