SPECIATION OF ARSENIC AND SELENIUM-COMPOUNDS BY ION CHROMATOGRAPHY WITH INDUCTIVELY-COUPLED PLASMA-ATOMIC EMISSION-SPECTROMETRY DETECTION USING THE HYDRIDE TECHNIQUE

Different forms (species) of arsenic and selenium play an important role in biological and environmental samples. For example, arsenic is widely dispersed in the environment by emission of about 32.10(6) kg/year as a result of anthropological inputs. The feasibility of species and multi-element determinations after ion chromatographic separation was investigated using inductively coupled plasma atomic emission spectrometry (ICP-AES) as an atomic spectrometric detection technique. After the separation of arsenic(III), arsenic(V), dimethylarsinic acid and selenium(IV) on an ion-exchange column PRP X-100 with a mobile phase of 1 mM p-hydroxybenzoate-0.4 mM benzoate at pH 8.5 the analyte ions were transferred to the hydride forms. The analyte gas was separated from the aquatic phase by a laboratory-made low-volume gas-liquid separation chamber. With optimized reagent concentrations of sodium borohydride and hydrochloric acid the efficiency of the hydride generation of the investigated compounds is in the range of 85 to 96%. Compared with the pneumatic nebulization, the sensitivity was increased by a factor of 50 using on-line post-column hydride formation. In addition, the parameters of the plasma, e.g. plasma power, argon gas flows and emission lines were optimized to achieve a high sensitivity of the ICP detection. The comparison of the sensitivities and reproducibilities shows the improvement by ICP-AES detection.