Simultaneous square wave anodic stripping voltammetric determination of Cr, Pb, Sn, Sb, Cu, Zn in presence of reciprocal interference: application to meal matrices

Abstract

An analytical procedure for simultaneously determining chromium(VI), lead(II), tin(II), antimony(III), copper(II) and zinc(II) by square wave anodic stripping voltammetry (SWASV) in matrices involved in foods and food chain as wholemeal, wheat and maize meal is described. The digestion of each matrix was carried out using a concentrated HCl–HNO 3–H 2SO 4 acidic attack mixture. Dibasic ammonium citrate buffer solution pH 6.5 was employed as the supporting electrolyte. The voltammetric measurements were carried out using, as working electrode, a stationary hanging mercury drop electrode (HMDE) and a platinum electrode and an Ag∣AgCl∣KCl sat electrode as auxiliary and reference electrodes, respectively. The analytical procedure was verified by the analysis of the standard reference materials Wholemeal BCR-CRM 189, Wheat Flour NIST-SRM 1567a and Rice Flour NIST-SRM 1568a. For all the elements in the certified matrix, the precision as repeatability, expressed as relative standard deviation ( s r) was of the order of 3–5%. The accuracy, expressed as relative error ( e) was generally of the order of 3–6%, while the detection limits were lower than 0.123 μg/g. In the presence of reciprocal interference, the standard addition method considerably improved the resolution of the voltammetric technique. Once set up on the standard reference materials, the analytical procedure was transferred and applied to commercial meals sampled on market for sale. A critical comparison with spectroscopic measurements is also discussed.