Shrivas Kamlesh, Wu Hui-Fen
Department of Chemistry, National Sun Yat-Sen University, Kaohsiung, 804, Taiwan.
J Mass Spectrom. 2007 Dec;42(12):1637-44. doi: 10.1002/jms.1266.
A rapid, simple, sensitive, and effective quantitative method for simultaneous determination of cationic surfactants (CS(+)) from river and municipal wastewater by direct combination of single-drop microextraction (SDME) with atmospheric pressure (AP)-MALDI mass spectrometry has been successfully demonstrated without the requirements of tedious sample pre- or post-treatment or separation by high-performance liquid chromatography (HPLC), gas chromatography (GC), and capillary electrophoresis (CE). This quantitative method can greatly enhance the signal-to-noise ratio for analysis of small molecules of CS(+) owing to the strong suppression of matrix ions by the analytes. In addition, SDME assisted in the isolation and preconcentration of CS(+) from water samples, which could effectively reduce the background interferences from the matrices present in waste and river water. The SDME conditions were optimized for achieving high extraction efficiency of CS(+) from aqueous samples, in terms of solvent selection, stirring speed, extraction time, exposure volume of acceptor phase, and salt addition. The enrichment factors for CS(+) were found to be 40-64-folds for 7 min of extraction time with no salt addition and at room temperature. This method was found to yield a linear calibration curve in the concentration range from 50 to 1500 microg/l CS(+) with a limit of detection (LOD) of 10 microg/l. The relative recoveries in river and municipal wastewater were found to be 93.8-103.6% and 91.0-98.7%, respectively. These results indicate that the combination of SDME with AP-MALDI/MS is effective for the simultaneous determination of CS(+) from river and municipal wastewater. In addition, a comparison of enrichments and LOD values for this method with hollow-fiber liquid phase microextraction (HF-LPME) was also demonstrated. The present approach is easy to operate, rapid, sensitive, and suitable for high-throughput of analysis.
一种快速、简单、灵敏且有效的定量方法已成功得到验证，该方法通过将单滴微萃取（SDME）与大气压（AP）-基质辅助激光解吸电离质谱（MALDI-MS）直接联用，可同时测定河流和城市污水中的阳离子表面活性剂（CS(+)），无需繁琐的样品预处理或后处理，也无需通过高效液相色谱（HPLC）、气相色谱（GC）和毛细管电泳（CE）进行分离。由于分析物对基质离子的强烈抑制作用，这种定量方法可大大提高CS(+)小分子分析的信噪比。此外，SDME有助于从水样中分离和预富集CS(+)，可有效减少废水和河水中基质产生的背景干扰。从溶剂选择、搅拌速度、萃取时间、接受相暴露体积和加盐等方面对SDME条件进行了优化，以实现从水样中高效萃取CS(+)。发现在室温下不添加盐的情况下，萃取7分钟时CS(+)的富集因子为40 - 64倍。该方法在50至1500微克/升CS(+)的浓度范围内产生线性校准曲线，检测限（LOD）为10微克/升。在河流和城市污水中的相对回收率分别为93.8 - 103.6%和91.0 - 98.7%。这些结果表明，SDME与AP-MALDI/MS联用对于同时测定河流和城市污水中的CS(+)是有效的。此外，还展示了该方法与中空纤维液相微萃取（HF-LPME）在富集和LOD值方面的比较。本方法操作简便、快速、灵敏，适用于高通量分析。
