Determination of arsenic, selenium and lead by electrothermal vaporization inductively coupled plasma mass spectrometry using iridium-coated graphite tubes

Iridium is proposed as a chemical modifier for the determination of Pb, As and Se by electrothermal vaporization inductively coupled plasma mass spectrometry. Iridium can be pipetted into the tube as a solution prior to the analytical or sample solution or the tube can be pre-treated with an Ir solution followed by the application of a heating program, forming an Ir coating, The latter procedure is preferred, since the modifier can be cleaned in the tube. More than 100 measurement-cycles can be performed with the same Ir coating, if resloping of the analytical curve is carried out for As and Se. For Pb, there is no need for resloping. A pyrolysis temperature up to 1300 degrees C can be used. The Ir-coated tube mas successfully applied to the determination of Pb, As and Se in several certified reference materials, viz., mater, estuarine mater and urine, For the urine sample, the analyte additions method was used, whereas for the water samples, external calibration was applied.