Improvement to sample introduction in plasma spectrochemistry with biological and environmental applications and potential for arsenic speciation in waters by anodic stripping voltammetry

Abstract

Methods for the determination of trace elements in environmental and biological samples were developed and optimized. Parameters affecting sample introduction efficiency, matrix effects, sample throughput and tolerance to interfering species were evaluated for methods based on plasma spectrochemistry and electrochemistry. A method was developed for the determination of copper in the presence of β-2-microglobulin. A mass balance of copper was performed at the end of in vitro incubations which required method development to quantify copper in the liquid and solid portions of the incubation solutions, along with copper adsorbed and mass transferred into the walls of the incubation vessel. A flow injection method was developed to accommodate the small sample volume and high dissolved solids content to allow for the determination of copper by ICP-MS. A commercial introduction system was evaluated for the determination of trace elements in drinking waters and wastewaters by ICP-MS and ICP-OES. Parameters including increased throughput, reduced memory effects, increased stability and lower reagent consumption were evaluated as the system was successfully applied to U.S. EPA Methods 200.8 and 200.7, respectively. Particular attention was paid to the retention of mercury and sodium and long term stability during the analysis of samples containing high total dissolved salts. Results obtained with the new introduction system were compliant with EPA Methods 200.8 and 200.7 while increasing sample throughput two- or three-fold and significantly reducing memory effects. A method was developed for the enhancement of signals for trace elemental analysis by DRC-ICP-MS. Signal enhancement was evaluated as instrumental and reaction gas parameters were optimized. Background noise levels remained relatively unchanged as signal intensities were improved, resulting in improved signal to noise ratios. The developed method was successfully applied to the determination of gold in synthetic geological samples. A method was developed for the preconcentration and speciation of arsenic by anodic stripping voltammetry using ion exchange resins. Ion exchange and instrument parameters were optimized. The developed method was successfully applied to the determination of arsenic(III) and arsenic(V) in waters without interference from problematic species such as Cu(II). Suitable detection limits were obtained and the method was validated using a certified reference material