Modification of the CV-AFS Determination of Total Mercury in Sediments

In the determination of total mercury in sediments by the GB method (GB/T 22105.1-2008), modification of the method of sample digestion was made in 2 respects: ① instead of heating in water-bath, the sample was soaked in mixed acid of HCl-HNO3 (3+1) overnight, and then made up to 50 mL directly with H2O. The supernatant was taken for the CV-AFS determination of total mercury; ② mercury(Ⅱ) in the sample solution was shown to be stable for at least 3d, and no addition of preservative and diluent was necessary. Linear relationship between values of fluorescence intensity and mass concentration of total mercury was obtained by the modified procedure in the range within 4.00 ng·L-1, with detection limit (3S/N) of 0.011 ng·L-1. In the determination of total mercury in sediments, precision was tested, giving values of intraday (n=6) and interday RSD′s (n=5) in the ranges of 1.1%-3.7% and 5.9%-7.0% respectively. As verified by t-test, no significant difference was found between the results found by the present method and the GB method.