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On-line preconcentration, speciation and determination of chromium by flame atomic absorption spectrometry(faas) and chemiluminescence

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2004
Sürdem, Sedat
Toxicological studies have shown that the degree of toxicity of some elements depends on the chemical form in which the element is present. Chromium (III) is considered as an essential micronutrient for human whereas chromium (VI) is a potentially carcinogenic agent. So the speciation of inorganic chromium in environmental samples is required for accurate assessment of pollution levels. The chromium content in natural water is usually very low, and a preconcentration is often necessary prior to the determination. A sensitive and selective preconcentration and speciation procedure is developed for the determination of trace and ultra trace amounts of chromium species by utilizing chemiluminescence (CL) and flame atomic absorption spectrometric (FAAS) techniques. The performances of amino silica-gel, amino sol-gel, mercapto silica-gel beads and metal oxides for solid phase extraction of chromium are examined either in column or batch type studies. Considering the advantage of concentrating Cr(III) and Cr(VI) ions separately simply by adjusting the pH of the medium, amino silica-gel resin is chosen in this study. The influences of different experimental parameters on the separation and preconcentration of chromium species such as pH, eluent concentration, flow rate, particle size of the resin are investigated. Chemiluminescence detection studies are performed by using the catalytic effect of Cr (III) on the reaction between luminol and hydrogen-peroxide and Cr (VI) is detected after reduction to Cr (III). Luminol and H2O2 concentrations and the pH of the medium are optimized to increase the sensitivity of the system. Chemiluminescence is inherently a very sensitive technique. When a preconcentration step is included in the CL mesurement of very low concentrations of chromium is possible to determine. Indeed, a 25-fold enhancement in sensitivity of chromium ions is