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 ro le in biological and environmental samples. For example, arsenic is wi dely dispersed in the environment by emission of about 32.10(6) kg/yea r as a result of anthropological inputs. The feasibility of species an d multi-element determinations after ion chromatographic separation wa s investigated using inductively coupled plasma atomic emission spectr ometry (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 o f 1 mM p-hydroxybenzoate-0.4 mM benzoate at pH 8.5 the analyte ions we re transferred to the hydride forms. The analyte gas was separated fro m the aquatic phase by a laboratory-made low-volume gas-liquid separat ion chamber. With optimized reagent concentrations of sodium borohydri de and hydrochloric acid the efficiency of the hydride generation of t he 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 pa rameters of the plasma, e.g. plasma power, argon gas flows and emissio n lines were optimized to achieve a high sensitivity of the ICP detect ion. The comparison of the sensitivities and reproducibilities shows t he improvement by ICP-AES detection.