Construction and Validation of a GC-ICP-MS Instrument for the Analysis of Organometals and other Trace Element Species

Alexander W. Kim

PhD – September 1993

Department of Environmental Sciences, University of Plymouth

in collaboration with

British Petroleum plc, U.K.

A capillary gas chromatography - inductively coupled plasma - mass spectrometry (GC-ICP-MS) method has been successfully developed for the separation and determination for a range of environmentally important organometallic species and metal complexes. The coupled technique gave reliable quantitative and qualitative chemical speciation information, providing detection limits in the low pg s-1 range, Gaussian peak shapes, good linear response, high chromatographic resolution, high signal to noise ratio and few polyatomic interferences.

The study involved the construction of progressively improved transfer lines and ICP torch designs. The final transfer line design which enabled a direct interface of the GC to the ICP-MS was of simple construction, strong, inexpensive, required a relatively short installation time (2 hours) and was capable of operation over a large temperature range (ambient to 550C). To enable ease of installation the ICP-MS was modified by removing a panel from the hood and torch box, through which the transfer line could pass. The ICP-MS was tuned using a cold mercury vapour generator.

Analysis of compounds with a relatively high retention index (RI) of up to 3422 was achieved using high temperature (HT) GC-ICP-MS. The transfer line was capable of eluting metalloporhyrins (RI>6000). However due to condensation effects within the ICP torch the analysis of metalloporphyrins using HTGC-ICP-MS was not achieved.

Following the development of the GC-ICP-MS system Figures of Merit were established for tetraethyllead, five organotin compounds, diethylmercury and metal containing complexes (ferrocene and nickel diethyldithiocarbamate).

The coupled technique was successfully applied to the determination of organometallic species in standard reference materials. These included tetraethyllead (in fuel) and organotin compounds (in two harbour sediments). Calibration techniques used were external calibration, standard additions and internal standards. The values obtained were in agreement with the certificate values within the confidence limits of the measurements.

With the eventual objective of extending this system to the determination of geologically important metalloporphyrin species, a HTGC method was developed. Retention indices for a range of authentic porphyrins standards were measured and the analysis of a porphyrin - containing shale is also described.

Copyright 1993 A.W. Kim. All rights reserved.

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