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Cite This: ACS Appl. Mater. Interfaces 2018, 10, 8359−8365
Metal−Organic Framework Modified Glass Substrate for Analysis of Highly Volatile Chemical Warfare Agents by Paper Spray Mass Spectrometry Elizabeth S. Dhummakupt,† Daniel O. Carmany,‡ Phillip M. Mach,‡ Trenton M. Tovar,† Ann M. Ploskonka,§ Paul S. Demond,‡ Jared B. DeCoste,† and Trevor Glaros*,† †
Research and Technology Directorate, U.S. Army Edgewood Chemical Biological Center (ECBC), Aberdeen Proving Ground, Maryland 21010, United States ‡ Excet, Inc. 6225 Brandon Avenue, Suite 360, Springfield, Virginia 22150, United States § Leidos, Inc., Edgewood Chemical Biological Center (ECBC), P.O. Box 68, Aberdeen Proving Ground, Maryland 21010, United States ABSTRACT: Paper spray mass spectrometry has been shown to successfully analyze chemical warfare agent (CWA) simulants. However, due to the volatility differences between the simulants and real G-series (i.e., sarin, soman) CWAs, analysis from an untreated paper substrate proved difficult. To extend the analytical lifetime of these G-agents, metal−organic frameworks (MOFs) were successfully integrated onto the paper spray substrates to increase adsorption and desorption. In this study, several MOFs and nanoparticles were tested to extend the analytical lifetimes of sarin, soman, and cyclosarin on paper spray substrates. It was found that the addition of either UiO-66 or HKUST-1 to the paper substrate increased the analytical lifetime of the G-agents from less than 5 min detectability to at least 50 min. KEYWORDS: mass spectrometry, metal−organic frameworks, volatile chemistry, paper spray, chemical warfare agents
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was then used to directly analyze in-gel proteins.17 More recently, Damon et al. increased the hydrophobicity of the paper substrate through treatment with silanes.18 This treatment was recently used in our laboratory to monitor enzyme activity. A recent publication by Wang et al. has demonstrated that zirconium (Zr)-based metal−organic frameworks (MOFs) can be integrated onto paper spray substrates for increased adsorption and desorption.19 Results from this study showed that UiO-66-treated paper demonstrated increased absorbance of drugs in complex matrices, like blood. MOFs are modular materials consisting of inorganic metal nodes, known as secondary building units (SBUs), connected together by multidentate organic linkers in a predictable crystalline manner.20,21 Many of these structures have void spaces leading to large internal surface areas and pore volumes. MOFs have applications in gas storage22,23 and separations,24,21,25−29 catalysis,30−32 sensing,33,34 and toxic gas removal.35,36 The amount of analyte adsorbed under a given set of conditions is dictated by the density of sites for the analyte to interact with and the energy of the intermolecular forces between the analyte and the active site. Farha and coworkers have shown that the Zr-based MOFs, including the
INTRODUCTION Recent world events, such as the Ghouta1 and Khan Shaykhun2 chemical attacks in Syria, have emphasized the need for more rapid and sensitive detection of chemical warfare agents (CWAs). Current fielded/onsite detection methods for nerve agents (i.e., sarin, soman, tabun) include three color detector paper, the residual vapor detection kit, the water poison detection kit, and sorbent tubes for gas chromatography mass spectrometry (MS) analysis.3 However, each of these methods has disadvantages including low specificity, inability of detecting all warfare agents, false positives, and long chromatographic analysis times.4,5 Paper spray (PS) is a substrate-based ambient ionization technique for mass analysis.6 This method requires little to no sample preparation, with the analyte directly sampled from the substrate while being rapidly (≈1 min) analyzed by MS. Previously, paper spray has been used to analyze bacteria,7 herbicides,8 drugs of abuse,9,10 and explosives,11 in addition to CWA simulants in biological matrices12 and aerosol samples.13 However, due to the volatility of G-agents,14,15 particularly sarin (GB), analysis from a sorbent-less capture method is difficult. Since the initial concept of paper spray ionization, a variety of modified papers have been created and tested for a wide range of applications. Narayanan et al. developed carbon nanotube (CNT) coated paper that allowed for successful paper spray ionization with low (
