Flow injection spectrophotometric determination of isoproterenol using an avocado ( Persea americana) crude extract immobilized on controlled-pore silica reactor

An enzymatic reactor was constructed by the immobilization of polyphenol oxidase (PPO) from avocado ( Persea americana) crude extract in an inorganic support of controlled pore silica (CPS), after a previous step of silanization. This inorganic support has been used as an excellent carrier to immobilize this enzyme and the enzymatic reactor was used in a flow injection system for the determination of isoproterenol in pharmaceutical products. The procedure is based on the oxidation reaction of this drug with immobilized PPO and the product obtained was monitored at 492 nm. This system presented an analytical curve from 1.23×10 −4 to 7.38×10 −4 mol l −1 isoproterenol with a detection limit of 6.25×10 −5 mol l −1. Recoveries of isoproterenol between 98.5 and 103.1%, a relative standard deviation (R.S.D.) less than 1% ( n=10) and 36 determinations per h were obtained.