Development of sheath‐flow probe electrospray ionization (SF‐PESI)

Abstract

Probe electrospray ionization (PESI) uses a sharp solid needle as electrospray emitter. This method was found to be applicable to the analysis of real-world samples with high concentrations of salts and detergents without sample pretreatment. Since PESI is only applicable to wet samples but not to dry samples, sheath-flow PESI (SF-PESI) has been developed. The metal needle was inserted into the fine plastic capillary with a protrusion of 0.1-0.2 mm from the capillary terminus. The solvent was supplied continuously through the capillary. At the lowest position of the probe, solvent flowing out from the capillary makes the sample wet and extracts the analytes from the surface. The extracted analytes were electrosprayed at the highest position of the needle. SF-PESI was successfully applied to samples such as narcotics, tablets, bill, fruits, potatoes, etc.