DIRECT DETERMINATION OF ARSENIC, CADMIUM, LEAD AND ZINC IN SOILS AND SEDIMENTS BY ELECTROTHERMAL VAPORIZATION AND INDUCTIVELY-COUPLED PLASMA EXCITATION SPECTROMETRY

The direct determination of volatile heavy metals (As, Cd, Pb and Zn) in soil and sediment samples by electrothermal vaporization and induct ively coupled plasma excitation atomic emission spectrometry (ETV-ICP- AES) has been demonstrated. By addition of toluene vapour to the inter nal furnace gas and sodium selenite to both solution standards and sol id samples the transport losses of analytes were considerably reduced. Three calibration methods, based on solution standards, addition of s tandard solutions to powder sample and variable mass of solid certifie d reference material have been investigated, and no characteristic dif ference was found in their performance. The relative deviations from t he certified concentrations range between -13 and +15% (most often les s than 7%), depending on the analyte. The background equivalent concen tration data were about 20-fold better for the solid sampling ETV than for the dissolution based pneumatic nebulization sample introduction method.