Enzymic determination of peroxides in non-aqueous media

A fast enzymic flow injection procedure was developed for the determination of peroxides in non-aqueous samples, The biochemical reaction is effected in a flow injection system using a non-covalently immobilized horseradish peroxidase reactor, followed by spectrophotometric monitoring of p-anisidine, The method provides a limit detection of 0.9 mu M for hydrogen peroxide, 2.6 mu M for tert-butyl hydroperoxide and 2.0 mu M for benzoyl peroxide with a maximum sampling frequency of 60 h(-1). The enzyme reactor exhibits enhanced stability in water-saturated toluene, being stable for more than 4 months, and during this period an average number of 250 reactions can be performed with 1 mg of enzyme (220 purpurogallin units). The method permits the determination of peroxide in olive oil and margarine samples without any chemical pre-treatment or extraction of the sample. An average recovery of 98% was found for the determination of hydrogen peroxide in 12 different types of olive oil samples spiked with known amounts of H2O2, indicating the applicability of the procedure to real sample analysis. The procedure was also applied to the determination of H2O2 in four olive oils and a margarine sample and the results were comparable to those obtained by the reference method.