to separate the sample into two phases. Twenty-five microlitres
of 30% (w/v) ammonium thiocyanate and 25 ll of 20 mmol/l
iron (II) chloride were added to the mixture. The reaction mixture
was allowed to stand for 20 min at room temperature prior to
reading the absorbance at 500 nm. The blank was prepared in
the same manner, except distilled water was used instead of ferrous
chloride. A standard curve was prepared using cumene hydroperoxide
at concentrations ranging from 0.5 to 2 ppm. PV was
expressed as mg cumene hydroperoxide/kg dry sample.