提出了结合表面活性剂、膜富集和紫外可见漫反射光谱测定水中痕量铅的方法.在pH 8.5的氨水氯化铵缓冲溶液中,剧烈搅拌下,铅与双硫腙形成疏水性的红色络合物,该络合物能够被混合纤维素酯膜富集,并且在非离子表面活性剂聚氧乙烯月桂醚(Brij-30)的存在下,该络合物被混合纤维素酯膜富集的效率得到了很大提高,然后待膜自然干燥后直接测得膜表面的漫反射光谱.本文对表面活性剂类型、表面活性剂浓度、反应酸度、双硫腙浓度和反应时间等条件进行了优化.研究结果表明,在最佳实验条件下,最大吸收波长为485 nm,在5～100 μg·L-1范围内铅离子的浓度与其络合物的吸光度呈良好的线性关系,相关系数的平方R2为0.990 6,检出限为2.88 μg·L-1.研究发现下列共存离子不干扰铅离子的测定:500倍的K+,Na+,Ca2+,Mg2+,NH4+,NO-3,Cl-,CH3COO-,SO2-4;10倍的Al3+(10%的NaF进行掩蔽),Fe3+(10%的NaF和酒石酸钾钠进行掩蔽),Hg2+和Zn2+(10%的NaSCN和酒石酸钾钠进行掩蔽);同等浓度的Cd2+,Cu2+.采用本方法测定瓶装水中的痕量铅,结果与石墨炉原子吸收光谱法(GFAAS)测定的结果基本一致,加标回收率在95.4%～104.5%之间,标准偏差(SD)在0.5～1.5 μg·L-1之间,说明本方法具有较好的准确性.本方法操作简单、灵敏度高,适用于瓶装水中痕量铅的测定。

In this paper,a method of determination of trace lead in water by UV-Visible diffuse reflectance spectroscopy combined with surfactant and membrane filtration enrichment was proposed.In the NH3·H2O-NH4Cl buffer solution with pH 8.5,the lead(Ⅱ) ion would react with dithizone to form the red complex under vigorous stirring,which is hydrophobic and can be enriched by the mixed cellulose ester membrane.In addition,the nonionic surfactant Polyoxyethylene lauryl ether(Brij-30) was added into the solution to improve the enrichment efficiency,then visible diffuse reflectance spectra of the membrane were measured directly after the membrane were naturally dried.We also optimized the reaction conditions which may affect the complexation reaction process,such as type of surfactants,the concentration of the surfactant,the reaction acidity,the concentration of dithizone as well as the reaction time.The research results show that under the optimum conditions,a good linear correlation between absorbance at 485 nm and concentration of lead in the range of 5.0～100.0 μg·L-1 was obtained with a squared correlation coefficient(R2) of 0.990 6,and the detection limit was estimated accordingly to be 2.88 μg·L-1.To determine real water sample,the interference from some potential coexisting ions was also studied at the optimal conditions when the concentration of lead(Ⅱ) ion standard solution was fixed to 20 μg·L-1.The results indicate that the following ions cannot interfere in the determination of lead with the proposed method:500 times of the K+,Na+,Ca2+,Mg2+,NH+4,NO-3,Cl-,CH3COO-,SO2-4;10 times of the Al3+(using 10% NaF as a masking reagent to avoid the interference);10 times of the Fe3+(using 10 % NaF and 10% sodium potassium tartrate as masking reagents);10 times of Hg2+ or Zn2+(using 10% NaSCN and 10% potassium sodium tartrate as masking reagents);the same amount of Cd2+,Cu2+.The proposed method was applied to the determnation of lead(Ⅱ) in bottled water as a real sample.The determination results show good agreements between the proposed method and graphite furnace atomic absorption spectrometry(GFAAS) method.The recoveries in case of spiked real samples were between 95.4% and 104.5%,and the standard deviations(SD) were between 0.5 μg·L-1 and 1.5 μg·L-1,which indicate that the method developed in the present work with advantages of accuracy,simpleness,sensitiveness are of potential application for the determination of trace lead in water samples.