Investigating Dioxins and PCBs analysis by APGC-Trapped Ion Mobility-Mass Spectrometry.

Abstract

Over the last few years, the combination of ion mobility with mass spectrometry has gained interest in a variety of analytical fields, including trace pollutants analysis in complex matrices such as environmental and food samples. This technique separates ions according to their ion mobility in the gas phase (diffusion speed under the influence of an electrical field in a pressurized cell) and provides an additional dimension to the traditional GC/LC-MS systems, a higher selectivity and a noise reduction which lead to signal-to-noise ratios improvement. Collision cross-section, which is related to the charge state, size, and shape of the ion can be derived from the measurement of ion mobility. Trapped Ion Mobility Spectrometer (TIMS) was recently introduced and offers a more compact design with an improved ion mobility resolving power (up to 400) compared to other commercially available IM instruments. As a recent technique, it still needs to make its proof in analytical chemistry while coupled to gas chromatography mass spectrometry using an APCI source. In this master thesis, we investigated the potential of the APGC-TIMS-MS coupling applied to small persistent organic pollutants (POPs) like dioxins and polychlorobiphenyl derivatives (PCBs). We found that a complete mobility separation of dioxins and PCB congeners was achievable in the CCS frame according to their chlorination degree, while non baseline separation was usually reached for isomeric congeners. We also highlighted issues with the IMS calibration in the present coupling and proposed different methods for on-line calibration. We produced data supporting that the calibration was truly dependent on the source conditions and that internal and external calibrations both fail to provide absolute and accurate CCS. Calibration based on the chemical background from the GC column (polysiloxanes), shows an interesting potential in this regard.