采用疏水性多孔滤膜对水样进行气液分离预处理,优化的预处理条件为:加入抗氧化剂除掉体系中带入的氧,设置加热温度为90 ℃,加热时间为60 min,50%(体积分数)磷酸溶液总量为20 mL(单次加酸量为2 mL)。采用亚甲基蓝分光光度法测定所得溶液中硫化物的含量。结果表明,硫化物标准曲线的线性范围为0.050~0.700 mg·L^-1,检出限为0.003 mg·L^-1。方法用于测定有证标准物质,测定值在认定值的不确定度范围内,相对误差为-1.9%~-1.6%;按照标准加入法对实际样品进行回收试验,回收率为90.6%~95.0%,测定值的相对标准偏差(n=6)为2.5%~4.6%。

Hydrophobic porous filter membrane was used for gas-liquid separation pretreatment for water samples. The optimized pretreatment conditions were follows: adding antioxidants to remove the oxygen introduced into the system, setting the heating temperature at 90 ℃ and heating time of 60 min, and 50% (volume fraction) phosphoric acid solution with a total amount of 20 mL (a single addition amount of 2 mL of acid). Sulfide in the obtained solution was determined by methylene blue spectrophotometry. As shown by the results, the linear range of the sulfide standard curve was 0.050-0.700 mg·L^-1, with detection limit of 0.003 mg·L^-1. This method was used for determination of certified reference materials, and the determined values were within the uncertainty range of the certified values, with relative error ranged from -1.9% to -1.6%. Test for recovery was made on the actual samples by the standard addition method, giving results in the range of 90.6%-95.0%, with RSDs (n=6) of the determined values in the range of 2.5%-4.6%.