Effect of sheathing the sample aerosol with hydrogen, nitrogen or water vapour on the analytical performance of solid sampling electrothermal vaporisation coupled to inductively coupled plasma optical emission spectrometry

Abstract

The effect on the analytical performance of solid sampling (SS) electrothermal vaporisation (ETV) coupled to inductively coupled plasma optical emission spectrometry (ICPOES) of introducing H₂, N₂ or water vapour into the central gas flow of the ICP torch via a sheathing device was evaluated. In the latter case, water exiting the spray chamber of a pneumatic nebulisation system was pre-evaporated through infrared heating of the sheathing device and base of the torch to 400 °C. Sensitivity and detection limit upon sheathing the aerosol with H₂, N₂ or water vapour were significantly improved for the 11 elements monitored compared to those with conventional SS-ETV-ICPOES. The greatest improvement in sensitivity and detection limit was obtained with a N₂ sheath: sensitivity improved 1.2–4 fold while detection limit improved 2–13 fold, depending on the element. The improvement of SS-ETV-ICPOES sensitivity and detection limit with sheathing gas or water vapour do not degrade accuracy, as verified through the multi-elemental analysis of a standard reference material (SRM) of soil using external calibration with another soil SRM and internal standardisation with Ar 763.511 nm emission line to compensate for sample loading effects on the plasma.