Simultaneous determination of chloride, bromide and iodide in snow fall by XRF after the precipitation of their silver salts

Abstract

Chloride, bromide and iodide in water were determined by XRF spectrometry after precipitation of their silver salts using silver nitrate. To a 50 cm3 of sample solution containing these halides less than 0.5 mg, a 3 cm3 of conc. nitric acid was added to be about 0.9 M nitric acid solution, in which a complex ion such as Ag2Cl+ can not be formed by adding excess silver ion. The solution was then cooled at 5°C for about 1 h. Then 1 cm3 of 0.5% silver nitrate solution was put into the solution and stirred with a magnetic stirrer for 5 min. A colloidal silver halide formed was filtered through a 0.45 μm membrane filter paper, and the precipitate on-the paper was dried at room temperature and subjected to XRF spectrometry. The calibration curve gave a straight line less than 100 μg, but a curved line in the region of 100~500 μg for chloride and a straight line less than 500μg for bromide and iodide. The limit of detection was 0.2 μg for chloride, 0.1 μg for bromide and 0.5 μg for iodide, and the precision falls less than 5.0% R.S.D. (n=5) for 10~80 μg of these halides, except for 10 μg of iodide (R.S.D. is 8.2%). Simultaneous determination could be carried out in a solution containing chloride, bromide and iodide with an error of ±3%. There were no interference in the presence of ions which exist in usual rain water. This method is rapid and convenient for simultaneous determination of chloride, bromide and iodide in rain water and satisfactorily applied to the analysis of snow. © 1987, The Japan Society for Analytical Chemistry. All rights reserved.