Electroactive Polymer-Based Spray Ionization for Direct Mass Spectrometric Analysis

Abstract

Electrochemically deposited electroactive polymer (EAP) films were investigated for their potential to enhance the performance of ambient ionization mass spectrometry (MS). Several EAPs of varying hydrophobicity were evaluated, including the superhydrophobic polymer poly­[3,4-(2-dodecyl­ethylene­dioxy)­thiophene] (PEDOT-C12). The EAPs were electropolymerized onto indium tin oxide-coated glass, placed in front of the inlet of a mass spectrometer, and charged to 3.5–4.5 kV. Analyte solutions were then applied to the surface, initiating ionization events. Analytes including peptides and small molecule pharmaceuticals were studied in 0.1% formic acid in methanol/water (“spray solvent”) as well as in synthetic biological fluid matrices, using both EAP spray ionization (EAPSI) and paper spray ionization (PSI). Each EAPSI analysis required as little as 0.1 μL of solution, and the resulting sprays were stable and reproducible. The sensitivity, limit of detection (LOD), and limit of quantification (LOQ) were evaluated using bradykinin, cannabinol, and cannabidiol, which were prepared in pure solvents, artificial urine, and artificial saliva. The limits of detection and quantitation for EAPSI were improved relative to PSI by 1–2 orders of magnitude for analytes prepared in methanol/water and on the same order of magnitude as PSI for analytes prepared in artificial saliva and urine. This EAP-based spray ionization technique offers possibilities for rapid MS analysis with small sample sizes, high accuracy, and miniaturization of MS instruments.

Applications of ambient ionization mass spectrometry in 2022: An annual review

“…Schematic of paper spray ionization in comparison to electroactive polymer‐based spray ionization. Reprinted with permission from Wang et al 169 . Copyright 2022 American Chemical Society.…”

“…introduced electroactive polymer‐based spray ionization (EAPSI), a technique aiming to improve the performance of PS ionization (Figure 4 ). 169 In EAPSI, an indium tin oxide‐coated glass slide is used as an electrode onto which the electroactive polymer and sample are applied, before the application of a high voltage to induce electrospray as in PS‐MS. Compared to PS‐MS, EAPSI achieved improved LODs and limits of quantitation for solvent‐based analytes, and similar performance for analytes in complex matrices (artificial saliva and urine).…”

“…Still, each year brings a wealth of new research striving to drive the field forward. The introduction of entirely new AIMS techniques has perhaps slowed in recent years, as efforts are increasingly focused on the improvement and enhancement of the existing tried and tested technology, though some novel techniques and variants of existing techniques have nevertheless emerged.Wang et al introduced electroactive polymer-based spray ionization (EAPSI), a technique aiming to improve the performance of PS ionization (Figure4) 169. In EAPSI, an indium tin oxide-coated glass slide is used as an electrode onto which the electroactive polymer and sample are applied, before the application of a high voltage to induce electrospray as in PS-MS.…”