新银盐法测定饮用水中砷的可行性及影响因素分析

目的 探讨新银盐法测定饮用水中砷的可行性，分析可能存在的影响因素。方法 在不同反应温度、酸度、锌粒的规格和加入质量、乙酸铅棉花填充质量和松紧度等条件下，测定饮用水中砷，观察上述处理因素对水砷测定结果的影响。水砷测定按照生活饮用水标准检验方法(GB/T 5750.6)中新银盐法进行。结果 反应温度在10 ～ 30℃时,样品回收率为75.3％ ～ 93.6％(F=9.21,P＜ 0.01)，最佳反应温度为25℃；硫酸加入量3.0～6.0 ml时，样品回收率为80.3％～ 91.6％(F=4.67,P＜0.05)，最佳反应酸度为5.0 ml。蜂窝状（直径0.2～0.3、0.3～0.4 mm）和纽扣状锌粒的回收率分别为87.2％、90.7％、83.0％，最佳规格为0.3～0.4 mm;锌粒加入质量在3～5g时，回收率分别为74.6％～91.7％，最佳加入质量为5 g。乙酸铅棉花的填充质量为25～100 mg时，回收率为79.6％～91.3％,最佳填充质量为50 mg;乙酸铅棉花塞入管内长度为0.5～2.0cm时，样品回收率分别为90.7％、92.5％、81.5％、74.2％，最佳松紧度为1.0 cm。砷化氢吸收液在室温20℃稳定5.0 h、25℃稳定4.0h、30℃稳定2.5 h。结论 在新银盐法测定中，必须控制反应体系中的温度、酸度、无砷锌粒的规格和加入量、乙酸铅棉花的填充质量和松紧度，才能确保测定结果的精密度和准确度。

Feasibility and influence factors of a new silver salt method for determination of arsenic in drinking water

Objective To 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. Conclusions In 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.