A portable capillary electropherograph equipped with a cross‐sampler and a contactless‐conductivity detector for the detection of the degradation products of chemical warfare agents in soil extracts

Abstract

A fully portable CE device equipped with a capacitively coupled contactless-conductivity detector and a cross-injection device is put to the test in laboratory conditions. The portable device is capable of working on batteries for at least 4 h. After that, its performance is strongly affected by the drop in the high-voltage output and analysis may be interrupted if its length exceeds a reasonable time. The concentration of the BGE affects both ionic strength and conductivity. Choosing an optimal concentration of BGE is therefore about finding a good compromise between selectivity and sensitivity. All experiments were performed using a mixture of histidine and MES with a concentration of 15 mM as BGE. The performance of the cross-injection device is optimized by the use of internal standards. Satisfactory reproducibility is gained as the RSD of peak areas is reduced to 8% or less. LODs for different phosphonic acids are in the range of 2.5-9.7 microM. For the analysis of adsorption of phosphonic acids in sand and loamy soil samples, calibration curves are constructed. Linearity in a measured concentration range of 10-100 microM is excellent, as the squares of correlation constants are approximately 1. The concentration analysis of phosphonic acids in soil extracts demonstrates that their adsorption curves in sand and loamy soil follow different adsorption isotherms.