On-Line Admicelle-Based Solid-Phase Extraction-Liquid Chromatography-Ionization Trap Mass Spectrometry for the Analysis of Quaternary Ammonium Herbici

Ion pair admicelle-based solid-phase extraction (SPE) is proved here to be a valuable strategy to concentrate quaternary ammonium compounds (quats; chlormequat, mepiquat, paraquat, diquat, and difenzoquat) from drinking water. The approach is based on the adsolubilization of quats-surfactant ion pairs on sodium dodecyl sulfate (SDS)- coated alumina at pH 2.0. The on-line coupling of admicelle-based SPE to liquid chromatography (LC)-electrospray ionization trap mass spectrometry (MS/ESI) permits the identification and quantification of quats at the levels required by the international recommended levels (0.1 �g/L). The concentration factor achieved is about 250 using 50-mL sample volumes. The detection limits range from 10 to 30 ng/L. On-line regeneration of the sorbent in each run is easily achieved by disruption of SDS admicelles with methanol and posterior coating of the alumina with SDS.