An improved method for the determination of aryl-4-hydroxylase activity

An improved method for separation of tritiated benzo[a]pyrene from tritiated water in the aryl‐4‐hydroxylase assay is presented. Quantitative retention of benzo[a]pyrene was obtained with mixed cellulose acetate and nitrate filters. Enzymatic activities obtained with this modification agreed well with those determined using the standard charcoal column extraction. This modification greatly reduces the time required to perform this assay, and allows for the determination of enzyme activity in a large number of samples.