The application of an argon/nitrogen inductively-coupled plasma to the analysis of organic solutions

A 4-kW argon/nitrogen inductively-coupled plasma (ICP) is used for multielement trace determinations in organic solutions. After optimization of the pneumatic nebulizer and ICP parameters, trace determinations at sub-mug/ml concentrations with relative standard deviations of 1% are possible. The first application described is the determination of a series of metals (Cd, Cu, Fe, Mn, Zn) after their isolation from the sample matrix by extraction of the ammonium pyrrolidinedithiocarbamate complexes into methyl isobutyl ketone. Alkali and alkaline-earth metal salts at 50-g/l. concentrations do not affect the method, which can be applied to trace determinations in industrial waste waters having high salt contents. The second application is the multielement analysis of oils. The samples are diluted 1:10 with xylene, and the detection limits for Al, Cu, Fe, Mg, Mn, Si and Zn are in the sub-mu/g range. The superior detection power of spectrographic ICP methods in comparison with photoelectric techniques using a monochromator and a polychromator is discussed. Oils of different viscosities can be analysed with use of the same calibration graphs. From experiments with a computer-controlled polychromator with background measurement facilities, it is concluded that the accuracy is improved if background measurements are made at wavelengths near the analytical lines, for each sample independently.