Hou Li, Shen Gang, Lee Hian Kee
Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore.
J Chromatogr A. 2003 Jan 24;985(1-2):107-16. doi: 10.1016/s0021-9673(02)01827-7.
Dynamic liquid-phase microextraction (LPME) controlled by a programmable syringe pump was evaluated for extracting pesticides in water prior to GC-MS analysis. A conventional microsyringe with a 1.3-cm length of hollow fiber attached to its needle was connected to a syringe pump to perform the extraction. The microsyringe was used as both the microextraction device as well as the sample introduction device for GC-MS analysis. The attached hollow fiber served as the "holder" and protector" of 3 microl of organic solvent. The solvent was repeatedly withdrawn into and discharged from the hollow fiber by the syringe pump. Pesticides were extracted from 4-ml water samples into the organic solvent impregnated in the hollow fiber. The effects of organic solvents, plunger movement pattern, agitation and extraction time were investigated. Good repeatabilities of extraction performance were obtained, with the RSD values ranging from 3.0% (alachlor) to 9.8% (4-chlorophenol) for the 14 pesticides; most RSD values were under 5.0%. The method provided a 490-fold preconcentration of the target pesticides. The limits of detection were in the range of 0.01-5.1 microg/l (S/N = 3) in the GC-MS selected ion monitoring mode. In addition, sample clean-up was achieved during LPME because of the selectivity of the hollow fiber, which prevented undesirable large molecules from being extracted. A slurry sample (mixture of 40 mg soil/ml of water) containing seven pesticides was extracted using this method which also gave good linearity and precision (most RSDs <7.0%, n = 3).
对由可编程注射泵控制的动态液相微萃取（LPME）进行了评估，用于在气相色谱-质谱（GC-MS）分析之前萃取水中的农药。将一根连接有1.3厘米长中空纤维的传统微量注射器连接到注射泵上进行萃取。该微量注射器既用作微萃取装置，又用作GC-MS分析的进样装置。连接的中空纤维充当3微升有机溶剂的“容纳器”和“保护器”。通过注射泵将溶剂反复吸入中空纤维并从中排出。将农药从4毫升水样中萃取到浸渍在中空纤维中的有机溶剂中。研究了有机溶剂、柱塞移动模式、搅拌和萃取时间的影响。萃取性能具有良好的重复性，14种农药的相对标准偏差（RSD）值在3.0%（甲草胺）至9.8%（4-氯苯酚）之间；大多数RSD值低于5.0%。该方法对目标农药进行了490倍的预浓缩。在GC-MS选择离子监测模式下，检测限在0.01 - 5.1微克/升范围内（信噪比S/N = 3）。此外，由于中空纤维的选择性，在LPME过程中实现了样品净化，可防止不需要的大分子被萃取。使用该方法萃取了含有七种农药的泥浆样品（40毫克土壤/毫升水的混合物），该方法也具有良好的线性和精密度（大多数RSD <7.0%，n = 3）。
