Arpa Çiğdem, Aridaşir Itır
Chemistry Department, Hacettepe University, Beytepe, 06800 Ankara, Turkey.
J Anal Methods Chem. 2018 Aug 1;2018:8951028. doi: 10.1155/2018/8951028. eCollection 2018.
Ultrasound-assisted dispersive liquid-liquid microextraction method based on solidification of floating organic drop and back-extraction (UA-DLLME-SFO-BE) technique was proposed for preconcentration of lead ions. In this technique, two SFODME steps are applied in sequence. The classical SFODME was applied as the first step and then the second (back-extraction) step was applied. For the classical SFODME, Pb ions were complexed with Congo red at pH 10.0 and then extracted into 1-dodecanol. After this stage, a second extraction step was performed instead of direct determination of the analyte ion in the classical method. For this purpose, the organic phase containing the extracted analyte ions is treated with 1.0 mol·L HNO solution and then exposed to ultrasonication. So, the analyte ions were back-extracted into the aqueous phase. Finally, the analyte ions in the aqueous phase were determined by FAAS directly. Owing to the second extraction step, a clogging problem caused by 1-dodecanol during FAAS determination was avoided. Some parameters which affect the extraction efficiency such as pH, volume of extraction solvent, concentration of complexing agent, type, volume, and concentration of back-extraction solvent, effect of cationic surfactant addition, effect of temperature, and so on were examined. Performed experiments showed that optimum pH was 10.0, 1-dodecanol extraction solvent volume was 75 L, back-extraction solvent was 500 L, 1.0 mol·L HNO, extraction time was 4 min, and extraction temperature was 40°C. Under optimum conditions, the enhancement factor, limit of detection, limit of quantification, and relative standard deviation were calculated as 81, 1.9 g·L, 6.4 g·L, and 3.4% (for 25 g·L Pb), respectively.
提出了一种基于漂浮有机滴固化和反萃取的超声辅助分散液液微萃取方法（UA-DLLME-SFO-BE）用于铅离子的预富集。在该技术中，依次应用了两个SFODME步骤。第一步采用经典的SFODME，然后进行第二步（反萃取）。对于经典的SFODME，铅离子在pH 10.0时与刚果红络合，然后萃取到1-十二醇中。在此阶段之后，进行第二步萃取，而不是像经典方法那样直接测定分析物离子。为此，用1.0 mol·L硝酸溶液处理含有萃取的分析物离子的有机相，然后进行超声处理。这样，分析物离子被反萃取到水相中。最后，直接通过火焰原子吸收光谱法（FAAS）测定水相中的分析物离子。由于第二步萃取，避免了FAAS测定过程中由1-十二醇引起的堵塞问题。考察了一些影响萃取效率的参数，如pH、萃取溶剂体积、络合剂浓度、反萃取溶剂的类型、体积和浓度、阳离子表面活性剂添加的影响、温度的影响等。实验表明，最佳pH为10.0，1-十二醇萃取溶剂体积为75 μL，反萃取溶剂为500 μL，1.0 mol·L硝酸，萃取时间为4 min，萃取温度为40℃。在最佳条件下，计算得到的富集因子、检测限、定量限和相对标准偏差分别为81、1.9 μg·L、6.4 μg·L和3.4%（对于25 μg·L铅）。
