Zhang Xiao-fang, Zhu Bi-lin, Li Wei, Wang Lei, Zhang Lei, Wu Ting, Du Yi-ping
Guang Pu Xue Yu Guang Pu Fen Xi. 2015 Jul;35(7):1944-8.
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 x 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 microg x L(-1) was obtained with a squared correlation coefficient (R2) of 0.9906, and the detection limit was estimated accordingly to be 2.88 microg x 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 microg x 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+, NH4+, NO3-, Cl-, CH3COO-, SO4(2-); 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 micro x L(-1) and 1.5 microg x 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.
本文提出了一种结合表面活性剂和膜过滤富集的紫外可见漫反射光谱法测定水中痕量铅的方法。在pH 8.5的NH₃·H₂O-NH₄Cl缓冲溶液中，铅（II）离子在剧烈搅拌下会与双硫腙反应形成红色络合物，该络合物具有疏水性，可被混合纤维素酯膜富集。此外，向溶液中加入非离子表面活性剂聚氧乙烯月桂醚（Brij-30）以提高富集效率，膜自然干燥后直接测量其可见漫反射光谱。我们还优化了可能影响络合反应过程的反应条件，如表面活性剂类型、表面活性剂浓度、反应酸度、双硫腙浓度以及反应时间。研究结果表明，在最佳条件下，485 nm处的吸光度与5.0 - 100.0 μg·L⁻¹范围内的铅浓度之间具有良好的线性相关性，相关系数平方（R²）为0.9906，据此估计检测限为2.88 μg·L⁻¹。为测定实际水样，在铅（II）离子标准溶液浓度固定为20 μg·L⁻¹的最佳条件下，还研究了一些潜在共存离子的干扰。结果表明，以下离子不会干扰所提出方法对铅的测定：K⁺、Na⁺、Ca²⁺、Mg²⁺、NH₄⁺、NO₃⁻、Cl⁻、CH₃COO⁻、SO₄²⁻的500倍；Al³⁺的10倍（使用10% NaF作为掩蔽剂以避免干扰）；Fe³⁺的10倍（使用10% NaF和10%酒石酸钠钾作为掩蔽剂）；Hg²⁺或Zn²⁺的10倍（使用10% NaSCN和10%酒石酸钠钾作为掩蔽剂）；相同量的Cd²⁺、Cu²⁺。所提出的方法应用于实际样品瓶装水中铅（II）的测定。测定结果表明所提出的方法与石墨炉原子吸收光谱法（GFAAS）之间具有良好的一致性。加标实际样品的回收率在95.4%至104.5%之间，标准偏差（SD）在0.5 μg·L⁻¹至1.5 μg·L⁻¹之间，这表明本工作中开发的方法具有准确性、简便性和灵敏性等优点，在水样痕量铅的测定中具有潜在应用价值。
