Sensitive determination of selenium by inductively coupled plasma mass spectrometry with flow injection and hydride generation in the presence of organic solvents

Abstract

Parameters for selenium determination in inductively coupled plasma mass spectrometry (ICP-MS) by pneumatic nebulization and flow injection with hydride generation (FI-HG-ICP-MS) have been compared. The effect of organic solvents (methanol, ethanol, propanol, acetone and acetonitrile) on the Se response has been evaluated with both sample introduction modes. Results show that the addition of alcohols leads to an important reduction of polyatomic interferences (⁴⁰Ar³⁷Cl, ⁴⁰Ar³⁸Ar, ⁴⁰Ar₂H₂) and to a 10-fold enhancement of the Se signal. The effect of the solvent on both signal enhancement and reduction of the interference mechanisms are discussed. Under optimized operating conditions (NaBH₄= 0.2%, pH1, methanol load = 6%), selenium determination by FI-HG-ICP-MS gives detection limits (3 s_b) of 1 pg for a 200 µl sample loop with an average RSD of <2% under routine conditions. This system has been validated by participation in a certification campaign throughout Europe for inorganic selenium. It has also been applied to the direct determination of dissolved Se^IV in natural estuarine waters.