Determination of selenium in garlic by cathodic stripping voltammetry

The selenium content in a garlic sample was determined on hanging mercury drop electrode (HMDE) using cathodic stripping voltammetry (CSV). In this method the dried garlic sample was digested in HNO3:HClO4 (1:1) by wet-digestion procedure. The CSV voltammogram in 0.1 M HCl solution showed a peak for Se at −0.56 V. Effect of deposition potential, deposition time and sweep rate on this peak were tried to determine the optimum experimental conditions. A deposition potential of −0.2 V was applied for 120 s while stirring the solution by passing nitrogen and followed a potential scan of 50 mV/s in a negative direction. The standard addition method was used to determine selenium in the sample. The linear domain range of Se (IV) was 2.0×10−8–6.0×10−7 M with a correlation coefficient of 0.9985. This method was used for the first time for the determination of selenium in garlic sample without any separation procedure and preconcentration techniques such as ion exchange, solvent extraction or hydride generation. The amount of selenium determined in three different samples from three different regions were 370±26 (n=5), 485±35 (n=4) and 365±46 (n=4) ng/g (dry-weight) with relative standard deviations of 7.0, 7.2 and 12.6%, respectively.