AFS Determination of Mercury in the Food-Additive Calcium Carbonate

Sample of the food-additive,calcium carbonate,was dissolved with HCl(5+95),and the content of mercury in the sample solution was determined by AFS.Experimental conditions,including lamp current negative high-voltage,height of atomizer,flow rate of carrier and shielding gas,concentration of the carrier medium and concentration of potassium borohydride,as well as the interferences of coexisting ions were studied and optimized.Linear relationship between values of fluorescence intensity and mass concentration of Hg was found in the range within 1.0 μg·L-1,with detection limit (3s/k) of 0.8 ng·L-1 .Test for precision was performed with 0.5 μg·L-1 Hg standard solution,the value of RSD (n=11) found was 0.95%.The proposed method was applied to the analysis of 2 calcium carbonate samples,and value of average recovery found by standard addition method was 103.5%.