Matrix-Compatible Solid-Phase Microextraction Pin Coupled Directly to Mass Spectrometry using Probe Electrospray Ionization

A solid-phase microextraction (SPME) pin device witha biocompatiblecoating on the tip was developed for direct coupling to mass spectrometry(MS) via a vertical dipping-and-spray strategy using an automatedprobe electrospray ionization (PESI) interface. The developed methodprovides superior sensitivity compared to standard PESI-MS due tothe enrichment effects of SPME and the significant increase in thevolume of sample and/or solvent collected during dipping due to theSPME pin's notably larger size. The tips of the SPME pins werecoated with a biocompatible coating consisting of small sorbent particlesembedded into a polyacrylonitrile (PAN) binder. This coating enablesthe extraction of small molecules, while preventing larger moleculessuch as tissue fragments, proteins, and cell matter from coming intothe sorbent. The developed SPME pin-PESI-MS method also features muchlower matrix effects compared to PESI-MS for the analysis of complexbiology samples. When applied for the analysis of 8 drugs of abusein urine samples, the SPME pin-PESI-MS method provided good linearity(R (2) >= 0.9997), high sensitivitywith limits of detection between 0.003 to 0.03 ng/mL, and good reproducibilitywith RSD% <= 6%. The vertical design of the SPME-PESI-MS direct-couplinginterface allows the potential fully automation of the system usinga conventional autosampler.