Modification of the Method for Determination of Total Mercury in Coal by Oxygen Flask Combustion

Modification of the method for determination of total mercury in coal by oxygen flask combustion was proposed. Coal sample was burned in a crucible heated electrically by nichrome wire in an oxygen flask. Mercury vapour evolved was absorbed in a solution of potassium permanganate in sulfuric acid (1+9). The divalent mercury ion in the solution after reduction of permanganate with hydroxylamine hydrochloride solution was ready for determination of its content by FI-HG-AAS (cold vapour). Linearity between the absorbance and concentration of mercury (expressed as μg·L-1) was obtained with a correlation coefficient of 0.999 7. In analyzing 10 portions of the same sample by the method proposed,average value of mercury content found was 0.558 μg·L-1 with RSD (n=10) of 4.8%. Test for recovery was made by addition of standard mercury solutions of 3 different concentrations to a same coal sample,and results obtained were in the range of 91.4%-97.3%. It was proved that this method is feasible for the routine analysis of large number of samples.