Direct analysis of surface chemicals using vibrating sharp-edge spray ionization mass spectrometry.

rationaleDirect analysis of chemicals on a surface using mass spectrometry (MS) is of great importance in forensics, food and drug safety, environmental monitoring, and defense. Solvent extraction-based surface analysis offers a convenient way of controlling the desorption conditions and applying internal standards. To date, it mainly relies on a separate electrospray process to nebulize and ionize the solvents. Here, we report a simple and stand-alone ionization system for the solvent extraction-based surface analysis without the need for high voltage, based on vibrating sharp-edge spray ionization (VSSI).

methodsWe modified the original VSSI device and developed a stand-alone, integrated surface sampling, and ionization system for MS analysis. By incorporating a micropipette-based solvent dispenser with the VSSI device, the new system performs solvent extraction and ionization, and still maintains a small footprint.

resultsWe demonstrated a four order-of-magnitude linear response for glucose spotted on a glass surface with a limit of detection (LOD) of 0.1 pg/mm

conclusionsWe have demonstrated a simple, effective, direct ambient-ionization method that is highly sensitive to molecules on a wide range of surfaces. The flexibility, small footprint, low cost, and voltage-free nature of this method make it an attractive technique for direct surface sample analysis using MS.