1979 Volume 28 Issue 11 Pages 695-699
A method for the selective determination of inorganic and organic mercury in aqueous solution is described. The method is based on the selective reduction of inorganic mercury with NaBH4 in an alkaline solution (pH 10), and based on the finding that both inorganic and organic mercury compounds are decomposed and reduced by a combined use of Fe(III) and NaBH4 in an aqueous solution of pH 28. The determination procedures are as follows: (A) Determination of inorganic mercury; An aliquot (100 ml) of sample solution was taken into a reaction vessel, and the pH of the solution was adjusted to 1012 with 1 N sodium hydroxide. To the solution 2 ml of 1% (w/v) NaBH4 solution was added, and the mixture was stirred for 5 min. Then the evolved mercury vapor was measured with an atomic absorption spectrophotometer. (B) Determination of total mercury; An aliquot (100 ml) of the sample solution was taken into the reaction vessel, and the pH of the solution was adjusted to 23 with 1 N sulfuric acid. To the solution 2 ml of 1×103 ppm Fe (III) and 2 ml of NaBH4 solutions were added successively, and the mixture was stirred for 5 min. Then the evolved mercury vapor was measured with the atomic absorption spectrophotometer. The organic mercury of the sample solution was determined by the differences between the values obtained by the above two procedures. The method is useful in the range of (0.28) ppb with a standard deviation of 2% at 5 ppb. The method was satisfactory for river and waste water samples.
