Purge-and-Trap Isothermal Multicapillary Gas Chromatographic Sample Introduction Accessory for Speciation of Mercury by Microwave-Induced Plasma Atomic Emission Spectrometry

Abstract

A compact device based on purge-and-trap multicapillary gas chromatography was developed for sensitive species-selective analysis of methylmercury and Hg2+ by atomic spectrometry. The operating mode includes in situ conversion of the analyte species to MeEtHg and HgEt2 and cryotrapping of the derivatives formed in a 0.53-mm-i.d. capillary, followed by their flash (< 30 s) isothermal low-temperature separation on a minimulticapillary (22 cm) column. The very low detection limits obtained (0.01 pg mL-1 of Hg for methylmercury) are due to the narrow injection band and reduced peak broadening in a bundle of 0.038-mm capillaries at high flow rates (> 60 mL min-1) compatible with an MIP AES detector (no dilution with a makeup gas is required). Developments regarding each of the steps of the analytical procedure and effects of operational variables (sample volume, purge flow, trap temperature, separation conditions) are discussed. The device allows speciation of MeHg+ and Hg2+ down to 5 pg g-1 in urine and, after a rapid microwave-assisted hydrolysis, down to 0.1 ng g-1 in solid biological samples with a throughput of 6 samples/h. The analytical protocols developed were validated by the analysis of DORM-1 (dogfish muscle), TORT-1 (lobster hepatopancreas), and Seronorm urine certified reference materials.