Thermospray device of improved design for application in ICP-MS

Abstract

A new thermospray device for sample introduction in ICP-MS has been developed. Three design principles were followed in order to minimize blank values which originate from chemical erosion of the utilized materials: the aerosol comes exclusively in contact with chemically inert materials; a fused silica capillary is used instead of the usually applied steel capillary; and a double desolvation system is applied for an effective reduction of the solvent load to the plasma. With careful optimization of the temperature of the capillary, aerosol gas flow rate, sample uptake rate, operation of the desolvation system and the ICP, a considerable improvement was achieved. Blank values in the mass region of Fe, as appear with steel capillaries, were reduced by orders of magnitude, so that this important region became accessible for analytical determination with satisfying detection limits. Sensitivity was improved by a factor of about 20 for the elements measured in comparison with two commercial pneumatic nebulization systems and ICP-MS instruments with low and high resolution. Standard deviations of ⩽3.8%, and about 10 times lower detection limits in the mean were achieved for a variety of elements in comparison with pneumatic nebulization. In spite of remaining restrictions from blank values, detection limits at pg ml^–1 levels and below were realized for several elements.