Determination of Cadmium and Lead in Concrete Roofing Tiles by Differential Pulse Anodic Stripping Voltammetric Method

Abstract

Differential pulse anodic stripping voltammetric method has been developed for determination of cadmium and lead released from concrete roofing tiles. The sample was extracted with water for 24 h according to the TIS 535-2540 standard method. An aliquot of 5 mL of the extracted solution and 5 mL of 4% v/v acetic acid solution were put in a voltammetric cell. Then, the solution was stirred at 2000 rpm and purged with nitrogen gas for 3 min before the deposition of the metals was carried out by applying a constant potential of -0.90 V versus Ag/AgCl to a hanging mercury drop electrode (HMDE) for 45 s. After that a differential pulse scanning waveform from -0.90 to -0.10 V was applied and a voltammogram was recorded. Peak current of cadmium and lead were measured at peak potentials of -0.555 and -0.364 V vs Ag/AgCl, respectively. Standard addition procedure was used for quantification. Relative standard deviation for 11 replicate determinations of 8 mgL-1 of both metals were in the range of 1.59 - 1.74%. Percentage recoveries obtained by spiking 8 mgL-1 of cadmium and lead to the sample solution were found to be 107% and with detection limit of 0.15 mgL-1 for both metals. It was found that contents of cadmium and lead released from the concrete roofing tile samples were in the range of < 0.15 - 0.49 mgL-1 and < 0.15 - 11.95 mgL-1, respectively, which are lower than the regulated values of the Thailand industrial standard (TIS 535-2540). The proposed method is simpler, more convenient and more sensitive than the standard method based on an atomic absorption spectrophototometry.