DEVELOPMENT OF A SEQUENTIAL INJECTION ANALYSIS (SIA) FLOW SYSTEM FOR THE DETERMINATION OF ZINC IN POWDERED MILK AND INFANT FORMULAE

The development and optimization of a sequential injection analysis (SIA) flow system is presented for the determination of zinc in milk powder and infant formulae. The determination is based on the reaction of Zn(II) with zincon at pH 9 in the presence of sodium citrate to mask the interfering matrix with spectrophotometric detection at 612 nm. The system was optimized by multivariate experiments. The validated system presented a linear range from 0.4 to 10 mg L-1 and the precision of the method was better than 5% (s(r)(%), n = 10). The detection limit was 0.13 mg L-1. The results obtained using the proposed and reference methods were found to be statistically equivalent. The sampling frequency was 75 samples per hour and the sample and reagent consumption of 0.24 mL per determination. The proposed method was accurate, simple, fast and according to the principles of green chemistry generating just 0.24 mL of chemical waste.