Comparison of pyrolysis and microwave acid digestion techniques for the determination of mercury in biological and environmental materials

Microwave digestion reduction-aeration and pyrolysis combined with cold vapour atomic absorption and cold vapour atomic fluorescence are compared for the determination of total mercury in several biological and environmental matrices. The biological samples were digested in a mixture of HNO3/H2O2, the environmental samples in a mixture of HNO3/HClO4. After reduction with SnCl2, the mercury was collected by two-stage gold amalgamation. After microwave digestion reduction-aeration, detection limits of 1.4 ng g(-1) and 0.6 ng g(-1) were obtained for cold vapour atomic absorption spectrometry (CVAAS) and cold vapour atomic fluorescence spectrometry (CVAFS), respectively, for 250 mg of environmental samples. For biological samples (500 mg) the detection limits were 0.7 ng g(-1) (CVAAS) and 0.4 ng g(-1) (CVAFS). After pyrolysis, detection limits of 3.5 ng g(-1) and 1.6 ng g(-1) for CVAAS and CVAFS, respectively, were obtained for a 10 mg sample. Pyrolysis can only be applied when the organic content of the sample is not too high. Accurate results were obtained for 8 certified reference materials of both environmental and biological origin. In addition, a real sludge sample was analysed.