Determination of zinc in pharmaceutical products by use of a sequential injection analysis system

A sequential injection analysis (SIA) system is proposed for the determination of zinc in pharmaceutical samples. The method is based on the spectrophotometric detection of zinc using xylenol orange as a colour reagent at 568 nm. The system can be used to monitor zinc at a frequency of 30 samples h(-1) with an average recovery of +/-98.5% and a relative standard deviation of less than 1%. A linear relationship between peak height and zinc concentration is obtained between 10 and 60 mg L(-1). The results obtained are in good agreement with those obtained by use of a standard method.