RESUMO
ObjectiveTo investigate the feasibility and influence factors of a new silver salt method for determination of arsenic in drinking water. Methods Arsenic was determined at different reaction temperature,acidity, specification and addition of zinc granular, fill weight of lead acetate cotton, and the effect of these factors on assay results was observed. Arsenic in drinking water was determined in accordance with standard test methods (GB/T 5750.6) of the new silver method. Results The recoveries of the arsenic were 75.3％ - 93.6％(F =9.21,P ＜ 0.01 ) with reaction temperature at 10 - 30 ℃, and the best reaction temperature was 25 ℃. The recoveries of the arsenic ranged from 80.3％ - 91.6％(F =4.67, P＜ 0.05) when sulfuric acid was 3.0 - 6.0 ml and the best value was 5.0 ml. The recoveries of the honeycomb structural zinc granular(diameter 0.2 - 0.3, 0.3 - 0.4 mm) and button zinc granular were 87.2％, 90.7％ and 83.0％, respectively; the best specification was 0.3 - 0.4 mm. The recoveries of zinc granular weight(3 - 5 g ) were 74.6％ - 91.7％, respectively; the best was 5 g. The recoveries ranged from 79.6％ - 91.3％ with fill weight of lead acetate cotton at 25 - 100 mg, the best fill weight was 50 mg.The recoveries of the arsenic were 90.7％, 92.5％, 81.5％ and 74.2％ with lead acetate cotton length at 0.5 - 2.0 cm,and the best loose-tight degree was 1.0 cm. The stability time of arsine solution was 5.0, 4.0, 2.5 h with corresponding temperature at 20, 25, 30 ℃, respectively. ConclusionsIn order to ensure precision and accuracy of the measurement, it is necessary to control reaction temperature, acidity, specification and addition of zinc granular free from arsenic, fill weight of lead acetate cotton and loose-tight degree in the reaction system.