A simple and rapid microwave-assisted extraction method using polypropylene tubes for the determination of total mercury in environmental samples by flow injection chemical vapour generation inductively coupled plasma mass spectrometry (FI-CVG-ICP-MS)

Abstract

Presented here is the development of a simple, rapid and cost-effective microwave-assisted extraction (MAE) method using closed polypropylene tubes (PP) and a domestic microwave oven for the determination of total mercury in a wide variety of environmental samples (coal, coal-fly ash, sediments and sludges). Extraction of mercury was achieved using microwave energy with a mixture of HNO₃–thiourea as extractant for subsequent determination by flow injection chemical vapour generation inductively coupled plasma mass spectrometry (FI-CVG-ICP-MS). Two types of reference materials certified for mercury; Coal fly ash NIST-1633b and estuarine sediment ERM-CC-580 were taken to optimize extraction parameters such as microwave power, extraction time and sample amount for the quantitative recovery of mercury. The supernatant obtained upon centrifugation was used for analysis. Quantitative recoveries of mercury were obtained using 30% HNO₃–0.02% thio-urea mixture with 30 s irradiation time at a microwave power of >640 W for 500 mg sample weight. The results obtained here were in good agreement with the certified values with an overall precision of better than 5% in all the cases. The limit of detection of the proposed method in conjunction with FI-CVG-ICP-MS was obtained to be 0.9 ng g⁻¹. A closed-microwave extraction procedure based on US EPA method (3051A) was used for the determination of mercury for comparison purposes. The optimized MAE procedure was successfully applied to real samples.