Speciation of mercury in coal using HPLC-CV-AFS system: Comparison of different extraction methods

Abstract

We propose an extraction methodology to extract toxic mercury species including methylmercury (MeHg) and ethylmercury (EtHg) in coal by comparing different extraction methods (shaking, ultrasonic and microwave assisted extraction) using different extraction solvents (TMA, KOH/CH₃OH, HCl, and acidic CuSO₄/KBr). Microwave assisted extraction at the power of 90 W for 5 min using TMA (tetramethylammonium hydroxide) as the extractant provided the highest and the most satisfactory extraction efficiency for MeHg and EtHg. Speciation analysis of mercury was done by HPLC-AFS. The obtained concentrations in a certified reference material (CRM-580) were in good agreement with the certificated values. Ten coal samples from China were analyzed using the proposed method. MeHg was detected in most of the samples (6 out of 10) and EtHg was detected only in one. The concentrations were at the sub-ng level. Other forms of organomercuries might be found in the samples. Considering the high toxicities of organomercuries and the huge amount of coal consumption every year, people should be made more aware.