Recent achievements in chemical hydride generation inductively coupled and microwave induced plasmas with optical emission spectrometry detection

Abstract

Although more than 30 years has already passed since hydride generation (HG) via the reaction with NaBH₄ (THB) was combined with inductively coupled plasma (ICP) and microwave induced plasma (MIP), and applied in optical emission spectrometry (OES) for measurements of As, Bi, Ge, Pb, Se, Sb, Sn and Te, it is still the technique of choice in lots of analytical tasks requiring determinations of trace and ultratrace levels of these elements. But even now, HG offers plenty of room for development and progression. The last couple of years brought several achievements that revitalize HG and open new areas of its application for ICP- and MIP-OES methods. New universal sample introduction interfaces, capable of operating as both conventional spray chambers for pneumatic nebulization (PN) and reaction cells and gas-liquid phase separators (GLSs) for HG, have made possible real simultaneous determinations of hydride and non-hydride elements. The scope of HG utilizing the reaction with THB has additionally been expanded to transition and noble metals, i.e., Ag, Au, Cu, Mn, Ni, Pd, Pt, Rh, Zn and other elements, which vapor species, possibly nanoparticles of reduced elemental forms, are formed and transported into the plasma prior to detection by OES. It also seems that HG is well suited for determinations of hydride and non-hydride forming elements from slurried sample solutions with no necessity for tedious and time-consuming preparations of samples aimed on their complete decomposition. Operation of HG in a flow injection (FI) mode and use of microcolumns (MCs) loaded with different sorbents was found to be very suitable for pre-concentration of hydride forming elements and their separation from transition metal ions being encountered as serious interferents in HG. By combining HG with high performance liquid chromatography (HPLC) or capillary electrophoresis (CE), speciation analysis of hydride forming elements was possible. This present review provides a literature survey on achievements in HG for ICP- and MIP-OES detection that have been made over the last few years. Different aspects of this technique, including design of HG reaction and separation systems, chemical reaction conditions, accompanying chemical interferences, means of their reduction, procedures of sample treatment for determinations of total concentrations and speciation forms of hydride and non-hydride forming elements in relevant samples, and figures of merit achievable with ICP and MIP, are described and discussed.