Xu Hui, Liao Ying, Yao Jinrong
Key Laboratory of Pesticide & Chemical Biology, Ministry of Education, College of Chemistry, Central China Normal University, Wuhan 430079, China.
J Chromatogr A. 2007 Oct 5;1167(1):1-8. doi: 10.1016/j.chroma.2007.08.022. Epub 2007 Aug 12.
A new sample pretreatment technique, ultrasound-assisted headspace liquid-phase microextraction was developed as mentioned in this paper. In the technique, the volatile analytes were headspace extracted into a small drop of solvent, which suspended on the bottom of a cone-shaped PCR tube instead of the needle tip of a microsyringe. More solvent could be suspended in the PCR tube than microsyringe due to the larger interfacial tension, thus the analysis sensitivity was significantly improved with the increase of the extractant volume. Moreover, ultrasound-assisted extraction and independent controlling temperature of the extractant and the sample were performed to enhance the extraction efficiency. Following the extraction, the solvent-loaded sample was analyzed by high-performance liquid chromatography. Chlorophenols (2-chlorophenol, 2,4-dichlorophenol and 2,6-dichlorophenol) were chosen as model analytes to investigate the feasibility of the method. The experimental conditions related to the extraction efficiency were systematically studied. Under the optimum experimental conditions, the detection limit (S/N=3), intra- and inter-day RSD were 6 ng mL(-1), 4.6%, 3.9% for 2-chlorophenol, 12 ng mL(-1), 2.4%, 8.8% for 2,4-dichlorophenol and 23 ng mL(-1), 3.3%, 5.3% for 2,6-dichlorophenol, respectively. The proposed method was successfully applied to determine chlorophenols in real aqueous samples. Good recoveries ranging from 84.6% to 100.7% were obtained. In addition, the extraction efficiency of our method and the conventional headspace liquid-phase microextraction were compared; the extraction efficiency of the former was about 21 times higher than that of the latter. The results demonstrated that the proposed method is a promising sample pretreatment approach, its advantages over the conventional headspace liquid-phase microextraction include simple setup, ease of operation, rapidness, sensitivity, precision and no cross-contamination. The method is very suitable for the analysis of trace volatile and semivolatile pollutants in real aqueous sample.
如本文所述，开发了一种新的样品预处理技术——超声辅助顶空液相微萃取。在该技术中，挥发性分析物通过顶空萃取进入一小滴溶剂中，该溶剂悬浮在锥形PCR管底部而非微注射器的针尖上。由于界面张力较大，PCR管中可悬浮的溶剂比微注射器中的更多，因此随着萃取剂体积的增加，分析灵敏度显著提高。此外，采用超声辅助萃取以及对萃取剂和样品进行独立控温，以提高萃取效率。萃取后，对负载溶剂的样品进行高效液相色谱分析。选择氯酚（2-氯酚、2,4-二氯酚和2,6-二氯酚）作为模型分析物来研究该方法的可行性。系统研究了与萃取效率相关的实验条件。在最佳实验条件下，2-氯酚的检测限（S/N = 3）、日内和日间相对标准偏差分别为6 ng mL⁻¹、4.6%、3.9%；2,4-二氯酚分别为12 ng mL⁻¹、2.4%、8.8%；2,6-二氯酚分别为23 ng mL⁻¹、3.3%、5.3%。所提出的方法成功应用于实际水样中氯酚的测定，获得了84.6%至100.7%的良好回收率。此外，比较了该方法与传统顶空液相微萃取的萃取效率；前者的萃取效率比后者高约21倍。结果表明，所提出的方法是一种很有前景的样品预处理方法，它相对于传统顶空液相微萃取的优点包括装置简单、操作简便、快速、灵敏、精确且无交叉污染。该方法非常适合分析实际水样中的痕量挥发性和半挥发性污染物。
