Simultaneous determination of lead, cadmium, copper and zinc in Infant formula by anodic stripping voltammetry

Abstract

Determination of trace elements in food is of great importance, as some of them have nutritional significance, whilst others are toxic. Long-term exposure to low levels of toxic metals could be important, especially in relation to children. Differential Pulse Anodic Stripping Voltammetry (DPASV) is applied to simultaneous determination of lead, cadmium, copper and zinc in dry ash infant formula in nitric acid at 450±50°C. Determination of the elements was made in acetate buffer (pH 4.7) with a scan rate of 60 mVs -1 and a pulse height of 50 mV by Hanging Mercury Dropping Electrode (HMDE). The solution was stirred during pre-electrolysis at -1150 mV (vs. Ag/AgCl) for 90 s and the potential was scanned form -1150 mV to +100 mV(vs. Ag/AgCl). Precision of the method, expressed by relative standard deviation for lead, cadmium, copper and zinc, was calculated as 4.5%, 3.5%, 3.2% and 5.6%, respectively. Under these conditions, the limits of detection were 0.005, 0.005, 0.01 and 0.05 mg/kg for lead, cadmium, copper and zinc, respectively. Concentrations of lead, cadmium, copper and zinc in one of the infant formulas available in Iran were 0.384±0.222, 0.359±0.215, 4.436±0.811 and 37.426±8.951 mg/kg (mean±SD), respectively. In our study the concentrations of lead and copper were found significantly higher than those of standard and labelled values (P<0.001), respectively. Therefore, infant formula manufacturers, by virtue of the role of their products in the infants’ nutrition, have been acutely aware for sometime of the need to guard against any heterogeniety and contaminants.