Abstract
A novel online combustion system was developed for the quantification of metals (Ag, Cd, Cr, Fe, La, Li, Mg, Ni, Pb, Y, Zn, and Zr) in volatile organic solvents such as acetone, methyl isobutyl ketone (MIBK), chloroform, dichloromethane, tetrachloroethane or trichloro-trifluoroethane. After combusting the sample aerosol in a commercial carbon analyzer oven in an oxygen-rich atmosphere, carbon dioxide and remaining oxygen were removed from the gas stream prior to the introduction into an inductively coupled plasma optical emission spectrometer (ICP-OES). The proposed combustion/carbon removal approach allowed stable operation of the ICP even when introducing highly volatile solvents that otherwise would have immediately extinguished the plasma. Analyte signals in halogenated solvents were found to be significantly higher than in non-halogenated ones and non-linear calibration functions were observed for all investigated analytes below 5 mg kg−1. Though a stable operation of the plasma was possible, the analyte signal intensities obtained in water were, depending on the element and the solvent, between 1.5 and 2800 times higher than in halogenated solvents.
Highlights
The introduction of volatile organic substances into the inductively coupled plasma (ICP) can be troublesome
Reduced plasma stability, structured plasma background from molecular species (e.g. C2 or CN bands), spectral interference by carbon and soot formation on the torch or the injector are some of the problems regularly encountered in inductively coupled plasma optical emission spectrometer (ICP-OES) when introducing larger quantities of carbon
Several factors contribute to these problems: for pneumatic nebulizers the nebulization efficiency of many organic solvents is much higher than for water because of the differences in density, viscosity and surface tension.[1,2]
Summary
The introduction of volatile organic substances (e.g. solvents) into the inductively coupled plasma (ICP) can be troublesome. The introduction of molecular gases like oxygen is known to affect the excitation properties of the ICP.[24] Compared to other approaches, where a small amount of oxygen[25,26] (a few mL minÀ1) was added to the intermediate or inner gas ow of the torch to avoid soot deposition, the setup used in this work operated at a much higher oxygen concentration to facilitate complete combustion and avoid soot-induced clogging of the oven.
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