Use of a partial filling technique and reverse migrating micelles in the study of N-methylcarbamate pesticides by micellar electrokinetic chromatography–electrospray ionization mass spectrometry

Ammonium perfluorooctanoate as a volatile surfactant for the analysis ofN-methylcarbamates by MEKC-ESI-MS

“…In the partial filling technique [4,[9][10][11], the capillary is initially filled with BGE that contains no SDS micelles. Then, the BGE with micelles is injected so that the capillary contains a micelle plug on the inlet side.…”

“…A further complication is that it is also possible that monomers of the surfactant reach the detector, since the micelles slowly break down during the analysis and migrate as surfactant monomers, which have a lower effective mobility than micelles (i.e., they move faster toward the detector) [9]. Molina et al [4] therefore found it necessary to decrease the SDS concentration from 40 to 20 mM, at the expense of the resolution. Another way of preventing micelles from entering the mass spectrometer is to change their electrophoretic velocity, so that they migrate toward the anode.…”

“…For both classes of analytes, they experienced a decrease in separation efficiency as compared to a similar MEKC-UV method, which again can be attributed to the moving SDS boundary. In addition, compounds that are strongly retained by the micelles can migrate away from the detector and thus are not detected [4]. High-molecular-weight surfactants, such as the sodium salt of butyl acrylate-butyl methacrylate-metacrylic acid copolymer (M r ,40 000) have also been used in MEKC-ESI-MS [13].…”

“…While CZE-MS is now considered to be an established technique for the analysis of small charged molecules [1], analysis of neutral molecules by MEKC-MS is yet to find widespread application. The main reason is that with ESI, the most popular ionization method for CE-MS, commonly used surfactants (e.g., SDS) and buffers (e.g., tetraborate, phosphate) can cause analyte signal suppression and contamination of the mass spectrometer [1,[4][5][6][7][8][9]. For instance, Cheng et al [6] analyzed 16 synthetic drugs, and found that, with SDS concentrations higher than 20 mM, the response for most analytes was less than 30% of the response when no SDS was present.…”

Development of Advanced Capillary Electrophoresis Techniques with UV and Mass Spectrometry Detection for Forensic, Pharmaceutical and Environmental Applications

“…However, it requires a complex series of steps to avoid MS contamination. Molina et al [143] reported three ways to couple micellar electrokinetic chromatography (MEKC) on-line with electrospray ionization mass spectrometry (ESI-MS) for the analysis of Nmethylcarbamate pesticides. A more stable electrospray performance was obtained;…”