Surface-Enhanced Transmission Mode Desorption Electrospray Ionization: Increasing the Specificity of Ambient Ionization Mass Spectrometric Analyses

Abstract

Fabrication and utilization of mesh materials specifically designed to capture analytes from solution facilitates the direct coupling of affinity capture and ambient ionization mass spectrometry via surface-enhanced transmission mode desorption ionization (TM-DESI). Incorporation of photolabile groups within the linkage between the mesh surface and the covalently modified reactive probe affords facile release of mass tagged analytes directly to mesh surfaces that have been rinsed free of matrix interferences. The approach introduces increased specificity to the already rapid TM-DESI analysis technique, resulting in a powerful tool for high throughput screening of targeted analytes. Specific capture of thiols is discussed herein, but the surface-enhanced TM-DESI technique can be readily extended to other functional groups by alteration of the capture agent.A new era of high-throughput mass spectrometry emerged with the nearly simultaneous introduction of two ambient ionization techniques: desorption electrospray ionization (DESI) 1 and direct analysis in real time (DART).2 Recognition of the enormous potential of these ionization methods has resulted in a growing number of related techniques, including ones that integrate laser desorption, the use of plasmas, and extraction methods.3 The most compelling motivations for ambient ionization mass spectrometry are the ability to analyze surfaces directly, the speed of the analysis and the elimination of difficult or time consuming sample preparation steps. Most ambient ionization methods require only seconds per sample, which is a substantial improvement in throughput compared to the multiple minutes required to separate and analyze components in GC-MS and LC-MS analyses. Moreover most of the cumbersome sample preparation steps such as derivatization reactions and extensive sample cleanup protocols are alleviated. Although one of the major benefits touted for ambient ionization mass spectrometric methods is the direct analysis of complex samples, the elimination of chromatographic separation generally results in reduced specificity and ion suppression for low concentration species. One set of performance metrics (i.e., specificity and/or sensitivity) has been compromised for another (i.e., analytical speed) in desorptionbased ambient ionization mass spectrometry. A newer variation of DESI, termed reactive DESI, has been previously reported to address this issue and exploits the addition of specific reagents to the spray solution that undergo ion/molecule reactions with the analytes of interest, thus offering improved selectivity and sensitivity for the detection of targeted molecules. [4][5][6] In the present report, a surface-enhanced DESI-MS strategy is described which allows selective Corresponding author: jbrodbelt@mail.utexas.edu. NIH Public Access Author ManuscriptAnal Chem. Author manuscript; available in PMC 2011 January 1. NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript capture, release, and analysis of targeted analytes fro...

Rapid and Selective Screening for Sulfhydryl Analytes in Plasma and Urine Using Surface-Enhanced Transmission Mode Desorption Electrospray Ionization Mass Spectrometry

“…The results presented here demonstrate that the increased selectivity afforded by analyte capture can be merged with the high throughput capabilities of ambient ionization mass spectrometry via the utilization of mesh substrates specifically designed to both chemoselectively capture target analytes from solution and integrate seamlessly to transmission mode desorption electrospray ionization mass spectrometry (TM-DESI-MS) 36–38. While broadly applicable, the present study focuses specifically on sulfhydryl analytes which are prevalent in pharmaceuticals and human metabolism 39–41.…”

Mass spectrometry imaging under ambient conditions

“…(Venter, et al, 2006) The effects of the nebulizing gas are clearly discernible is the absence of any overt coulombic effect. The performance and characteristics of DESI were found to be dependent on the choice of the solvent (Tawiah et al, 2010), substrate (Ifa et al, 2008; Kauppila et al, 2006), and geometry (Chipuk et al, 2010; Kertesz & Van Berkel, 2008; Venter & Cooks, 2007). Experiments on solvent composition showed that different chemical information can be obtained by changing the solvent system.…”

Polymer‐spray mass spectrometric detection and quantitation of hydrophilic compounds and some narcotics

“…An important feature of sampling materials for ambient ionization mass spectrometry is their polarity. Hydrophobic materials such as polymethylmethacrylate and polytetrafluoroethylene have been shown to have enhanced signal intensity and stability over less hydrophobic materials used in desorption ionization techniques . Paper coated with a variety of different compounds has also been shown to have enhanced performance as sample support in paper‐spray mass spectrometry .…”