Application of gas chromatography-hybrid chemical ionization mass spectrometry to the analysis of diclofenac in wastewater samples

Abstract

Hybrid chemical ionization (HCI), a new and useful alternative to conventional chemical ionization mass spectrometry, has been applied to the analysis of the pharmaceutical diclofenac in wastewater samples. This technique takes advantage of the high versatility of ion trap (IT) spectrometers combined with external ionization sources. In hybrid configuration, reagent ions are generated in the external source through electron ionisation (EI) of a reagent gas. These reagent ions are then drawn into the ion trap and only those selected are allowed to react with analytes eluting from the GC column. These ion-molecule reactions create analyte ions which are held in the ion trap. In this study ion-molecule reactions between C 3F 5 + cations, generated from perfluorotributylamine (FC43), and diclofenac molecules have been investigated. The observed reaction products were [ M + C 3F 5–H 2O] + adduct ions, which result from the initial electrophilic addition of C 3F 5 + cations to the diclofenac molecule followed by the rapid loss of H 2O. Further fragmentation of these ions by MS/MS yielded enough daughter ions for a reliable identification of diclofenac in complex matrices. The GC–HCI–MS/MS method applied to wastewater samples provided highly enhanced selectivity and sensibility, with a detection limit in real samples of 3.0 ng/L, for a solid-phase extraction (SPE) pre-concentration factor of 400. Other performance characteristics of the method, such as linearity and precision were also satisfactory. Finally, the method was successfully applied to the analysis of wastewater samples taken from the effluent of an urban sewage treatment plant (STP).