Mercury determination in sediments by CVAAS after on line preconcentration by solid phase extraction with a sol-gel sorbent containing CYANEX 471X®

Abstract

The development of a preconcentration method for the measurement of trace levels of mercury in digested sediments is described. Solid phase extraction (SPE) was used for the preconcentration of mercury coupled on-line by means of a flow injection (FI) system followed by cold vapour atomic absorption spectrometry (CVAAS) detection. The SPE was carried out through a column packed with a sorbent material containing triisobutylphosphine sulfide (CYANEX 471X®) as mercury extractant and prepared by the sol-gel process. The effects of FI variables (argon, eluent, and reductant flow rates, loading and elution times) as well as the eluent concentration on the analytical performance of the method were evaluated. The proposed method was validated under the optimum conditions. The calibration graph was linear from 0.05 µg L⁻¹ to 3.0  µg L⁻¹ of Hg. The detection limit (DL), based on three times the standard deviation of the blank measurement criterion, was 24 ngL⁻¹. The repeatability was 1.5% and 1.8% RSD (n = 10) at concentrations of 0.5 and 1  µg L⁻¹ of Hg, respectively. Method enrichment factors of 16 with a productivity of 30 samples h⁻¹ or 32 with a productivity of 17 samples h⁻¹ were achieved under selected conditions. Certified reference materials, inductively coupled plasma mass spectroscopy (ICP-MS) and cold vapour atomic fluorescence spectrometry (CVAFS), were used to evaluate the accuracy of the proposed method.

Keywords:

• mercury
• preconcentration
• sol-gel
• sediments
• cold vapour atomic absorption spectrometry

Acknowledgements

The authors wish to thank the financial support given by CONACyT (Project 38061-U and scholarship), DGEP-UNAM, PAEP-UNAM, DGAPA (Project IN106802) and CENAM. Thanks are also due to CNA (Comisión Nacional del Agua) of Queretaro, México for sampling technical support, and Centro Experimental Oaxaca del Consejo de Recursos Minerales for the CVAFS mercury measurements.