Comparative study of different thermospray interfaces with carbamate pesticides: Influence of the ion source geometry

Abstract

Sixteen carbamate pesticides that belong to four chemical classes (oxime-N-methylcarbamates, aryl N-methylcarbamates, N-phenylcarbamates, and methyl esters of substituted carbamic acids) were investigated via three different commercially available thermospray interfaces and ion sources that exhibit wide differences in source geometry. Comparisons were made between the three interfaces with respect to ion formation and sensitivity of detection. Experimental parameters were standardized to obtain comparable experimental conditions. Very similar mass spectra for most carbamates were obtained that illustrate independence from the geometry of the ionization and desolvation chambers of the interfaces. These findings are in sharp contrast to several literature reports. However, thermally labile carbamates gave unsatisfactory results with regard to spectral compatibility between the interfaces. Such differences were due to thermally assisted hydrolysis reactions that occur in the vaporizer probe prior to ionization and reflect differences in the vaporizer designs. The study proves conclusively that comparable spectra can be obtained under thermospray with different interfaces and mass spectrometers.

Choosing between Atmospheric Pressure Chemical Ionization and Electrospray Ionization Interfaces for the HPLC/MS Analysis of Pesticides

“…Second, a number of papers have reported methods without summaries of the strength and weaknesses of APCI and ESI for pesticide analysis. There are, in fact, only a limited number of studies that compare the best conditions for optimal sensitivity for a small number of pesticides. , Third, although theoretical explanations of ionization using APCI and ESI have been given in a series of papers, − and the differences between them are clear, there is no well-defined procedure to select the most effective interface for pesticide analysis on the basis of chemical structure. For these reasons, it is a common procedure to try both APCI and ESI on a new pesticide in both positive and negative modes and “see what works best”.…”

Analysis of priority pesticides and phenols in Portuguese river water by liquid chromatography-mass spectrometry

“…This could be related to the interface design as have been observed previously in a comparative study about the influence of ion source geometry, e. g., the influence of different thermospray interfaces [20]. However, in general, better sensitivities were obtained with the HP instrument compared to the Platform.…”

Trace Level Determination of Organophosphorus Pesticides in Water with the New Direct-Electron Ionization LC/MS Interface

“…Electrospray ionization has a solid reputation for the analysis of trace-level contaminants, but the very low polarity does not allow a quantitative detection of organophosphorus pesticides. Several papers have been published on the use of particle beam (PB) − and thermospray (TSP) − for the analysis of pesticides, and some of these methods were validated by the Environmental Protection Agency (EPA) as recommended protocols for environmental monitoring. In some cases, GC with flame photometric (FPD), nitrogen−phosphorus (NPD) or MS detection can be advantageously used in the determination of organophosphorus pesticides, as demonstrated by many papers in the literature. − HPLC methods coupled with MS represent a valid alternative to GC/MS, since some of such compounds are thermally labile or chemically reactive and may decompose during analysis, leading to poor recoveries .…”