Determination of toxic elements (As, Bi, Cd, Pb, Sb, Se, Te) in spent automobile catalysts by high-resolution continuum source graphite furnace atomic absorption spectrometry with and without chemical separation: Precise method development and validation
Description
This work first describes the development, optimization, and validation of high-resolution continuum source graphite furnace atomic absorption spectrometry (HR CS GFAAS) for the determination of TE As, Bi, Cd, Pb, Sb, Se, Te in spent autocatalysts. HR CS GFAAS enables fast and reliable determination of these TE, and this method can be employed in recycling and transboundary movement of spent autocatalysts. A fast and efficient microwave digestion method was developed for the simultaneous transfer of analytes from autocatalysts into solution. The possibility of direct HR CS GFAAS determination of analytes from solution of spent autocatalysts was evaluated. For this purpose, the matrix effect of the samples on the HR CS GFAAS determination was examined. Due to the high concentrations of Pb in the samples (up to 0.5 % of the weight), it can be determined by HR CS GFAAS, after diluting the initial sample by no less than 25 times, which makes it possible to minimize the influence of the matrix. High precision method of direct HR CS GFAAS determination of Pb was developed (RSD not higher than 3 % in the concentration range 0.0005-0.5 % weight). Original in-house developed granular heterochain polymer S, N-containing hybrid sorbent was synthesized to determine other analytes. We investigated the effect of acidity of chemical environment (0.1-3M HCl), effect of extraction time (10-90 min), sorption capacity and selectivity, and the matrix effect of the sorbent on the determination of analytes. It was found that As, Bi, Cd, Sb, Se, Te could be quantitatively (degree of sorption 95-100 %) and simultaneously concentrated and separated from other elements of spent automobile catalysts, within 40 minutes. The sorption capacity of the sorbent for the determined TE varies from 0.05 to 0.15 g g-1. It was demonstrated that the sorbent does not sorb Al, Mg, Ce, Zr, Ti, Mn, Si; it partially sorbs Ni (degree of sorption no more than 0.5%) and Fe (degree of sorption ~ 1%). The matrix effect of the sorbent on the determination of analytes was not identified. Based on these findings, an advanced HR CS GFAAS method for TE determination was developed (RSD not higher than 4 % in the concentration range 1•10-6-1•10-3 % weight). The analytical possibilities of this advanced HR CS GFAAS were also studied. Limits of quantification (LOQ) (μg L-1) were: 0.5 (As), 0.8 (Bi), 0.006 (Cd), 0.8 (Pb), 0.5 (Sb), 0.6 (Se) and 0.7 (Te). Correlation coefficients were 0.9988, 0.9997, 0.9981, 0.9995, 0.9997, 0.9979 and 0.9996 respectively, for As, Bi, Cd, Pb, Sb, Se and Te. Linear range (μg L-1) was: LOQ-300; LOQ-100; LOQ-10; LOQ-100; LOQ-250; LOQ-300; LOQ-250 for As, Bi, Cd, Pb, Sb, Se and Te, respectively.