Development of a method for the spectrophotometric determination of arsenic.
A simple and inexpensive method for the determination of arsenic at low ppb levels was developed. The method is based on reduction of arsenite and arsenate in acidic reaction medium to the formation of hydride from sample solution, and its reaction with mercury bromide. Mercury bromide was impregnated on a solid support (filter paper), and formation and detection of a yellow-brownish product was performed spectrophotometrically by using an instrument for field determination of arsenic, Supralab FD. Amidosulfonic acid was used to adjust acidity of the solutions, and reduction of arsenic compounds was done by sodium borohydride. The method was used for the determination of arsenic in soil samples after digestion. The accuracy of the method was determined by analysis of a soil sample reference material (SRM 2710), and by an interlaboratory comparison. Detection limit of the method is 0,06 μg As/dm with limit of quantification of 0,2 μg As/dm.