|Direct Coupling of Solid Phase Microextraction to an Active Capillary Plasma Ionization Source for High-Throughput Trace Analysis in Solid and Liquid Matrices
|Mr Mario Mirabelli
Prof Renato Zenobi
Abstract Information :
The ability to perform a fast and simple trace analysis has become a necessity in numerous
fields, such as biomedical, forensic, food, and environmental analysis. Our approach to
address this demand involves the direct coupling of solid-phase microextraction (SPME) to a
very efficient active capillary plasma ionization source based on a dielectric barrier discharge
(DBD). This coupling enables an automated, quick, sensitive, and robust detection of
compounds of interest. The versatility and sensitivity of our source and approach were
previously demonstrated, for example for the sub-ng/L detection of pesticides.
Nonetheless, poorer ionization efficiencies for low-polarity compounds (such as polycyclic
aromatic hydrocarbons, PAHs) precluded their detection at comparably low levels. By
studying the effect of solvents on the ionization, both from a mechanistic as well as a
practical point of view, we were able to boost the ionization efficiency for PAHs and lower
the detection limits into the ng/L range.
This allowed us to develop a variety of different high-throughput trace level screening methods in both liquid and solid matrices. For example, a robust method for the detection of organic contaminants in water matrices was developed, requiring a total analysis time of less than 10 minutes per sample and achieving ng/L detection limits both for polar as well as non-polar substances. We also addressed the area of sports doping analysis, a field in which a large amount of samples needs to be screened at various events (e.g., Olympics) and thus enormously benefits from the remarkable speed of our approach. Finally, the applicability of our set-up for the analysis of solid matrices was also investigated, and a successful detection of μg/L levels of pesticides from soils and fruits was achieved with minimal sample preparation. The analysis of solid matrices usually requires lengthy and sample preparation intensive methods, the simplicity and speed of our approach thus provides a very interesting alternative.