Trace metal analysis of fresh and canned food samples by anodic stripping voltammetry

Abstract

The objectives of this study were to develop the parameters of an electroanalytical method, DPASV, for the determination of trace elements Zn, Cu, Pb and Cd in fresh and canned food samples, and to compare the new method with the conventional one, ICP-OES. Fresh fish samples were purchased from the local markets of Gelibolu, Çanakkale, and from groceries in Istanbul. Fish and vegetable samples in canned packages were analyzed. Samples were weighed in three replicates of about 1.50 – 2.00 g, and air dried. Samples were digested in nitric acid (HNO3) and nitric acid/perchloric acid (HNO3/HClO4) mixture (5/1, v:v). HNO3/HClO4 combination was found to be the most suitable to destroy the organic components of the food samples. DPASV parameters were optimized at 120 s of deposition time with Hanging Mercury Drop Electrode (HMDE), and 10 s of equilibration time and 1.8 s of voltage step time with Static Mercury Drop Electrode (SMDE). Supporting electrolytes of varying compositions at different pH levels (1.92, 4.60, and 8.40) were tested. Oxalate buffer, pH of 1.92, yielded the most precise and the accurate voltammetric peaks. In the presence of relatively high Zn and Cu concentrations, DPASV analyses were run separately by adjusting the corresponding deposition potential, and the mode of the mercury electrode. In the presence of relatively high Cu concentrations, DPASV analyses were done separately with the addition of a complexing agent, ethylenediaminetetraacetic acid (EDTA) at various concentration levels. Results of the ICP-OES and DPASV analyses were compared with each other; data sets were statistically analyzed with paired t-test. Statistical analysis at 95% confidence level showed that the results of the two methods were similar except the Pb contents of fresh and canned fish samples. Also, trace element concentrations in the food samples were investigated whether the recorded amounts were within the limits that were legislated by World Health Organization, European Union, and Turkish Food Codex or not.