A direct method for the determination of selenium and lead in cow's milk by differential pulse stripping voltammetry

The selenium and lead contents in milk samples from Turkey were determined using a hanging mercury drop electrode(HMDE) and differential pulse cathodic stripping voltammetry (DPCSV) and differential pulse anodic stripping voltammetry( DPASV), respectively. In this method, the milk samples were digested in HNO3 : HClO4 (1:1)mixture by a wet digestion procedure. The DPCSV of milk samples in 0.1 M HCl solution showed a peak for selenium at -0.56 V, and DPASV for lead showed a peak at -0.35 V. A deposition potential of -0.2 V for selenium, and -0.5 V for lead were suitable. The standard addition method was used to determine selenium and lead in the sample. The linear domain range was 75-1.2 mu g/l for selenium with a correlation coefficient of 0.9981 and 185-8.7 mu g/l for lead with a correlation coefficient of 0.9945. The proposed method provides a simple and suitable procedure for the determination of trace amounts of selenium and lead. In this method, there is no need for sophisticated instruments and tedious separation procedure. Selenium and lead contents of milk samples from three distinct regions of Turkey were obtained between 21.5-69.4 and 22.1-59.2 mu g/l (n = 4-5), with the relative standard deviations of 10.3-10.7 and 6.8-9.9%, respectively. (C) 2000 Elsevier Science Ltd. All rights reserved.