Determination and speciation of organotin compounds by gas chromatography—microwave induced plasma atomic emission spectrometry

Abstract

An optimized analytical method for the determination of organotin compounds in environmental samples is described. After derivatization the resulting compounds were measured with a hyphenated technique, gas chromatography coupled with element-selective detection by helium atmospheric pressure microwave induced plasma atomic emission spectrometry (GC—MIP-AES). The sensitivity of the most intensive emission lines in the range of 180–350 nm was investigated. The best results were obtained by using the 326.23 nm line. The influence of the reagent gases (H 2,O 2) on the signal intensity was determined. After the optimization of the source conditions a calibration was realized on the base of a multicomponent standard solution, prepared by pentylation of organotin salts. A detection limit of 0.8 pg Sn could be achieved. Measurements of the sensitivity on mixtures of organotin compounds with different alkylation showed a dependence of the grade of pentylation. This could be caused by plasma effects (formation of CO and OH molecular bands). The proposed method was applied to the analysis of organotin compounds in a sediment of the Elbe river. Furthermore, a new arrangement of GC—MIP-AES was studied. It consists of a gas chromatography, directly coupled to a newly designed MIP (without interface) and a quartz fibre optics to transmit the emitted light to the spectrometer. Parameters, such as gas flow, power of the microwave generator, distance of the capillary column to the plasma, were optimized.