Development of Hydride Generation/Low-Pressure Helium ICP-MS for the Determination of Selenium

Abstract

Low-pressure helium ICP-MS provides some advantages including effective ionization, negligible spectral interference and low consumption of plasma gases. The conventional nebulizers, however, are not useful for introducing aqueous sample solutions. In the present study, therefore, hydride generation was examined as a sampling technique for the determination of selenium. Traces of selenium in a stream (0.5 mL min^-1) of aqueous solution were converted into selenium hydride in coiled PVC tubes (4 mm i. d.×0.5 m and 4 mm i. d.×1.5 m) with 2 mol dm^-3 HCl and 1 w/v% NaBH₄ aqueous solution. The volatile hydride was separated from the solution and transferred into a low-pressure helium ICP through a glass capillary tube (0.2 mm i. d.×40 mm) with the aid of helium carrier gas at a flow rate of 100 mL min^-1. The mass spectra obtained show that ⁸⁰Se⁺ (generated from the most abundant isotope)is successfully determined with the excellent S/B ratio, otherwise not measured as is the case with conventional argon ICP due to serious isobaric interference.