Abstract
Solid-phase microextraction (SPME) is directly integrated with low temperature plasma ionisation mass spectrometry to rapidly detect organophosphate chemical warfare agent simulants and their hydrolysis products in chemical mixtures, including urine. In this sampling and ionization method, the fibre serves: (i) to extract molecules from their native environment, and (ii) as the ionization electrode that is used to desorb and ionize molecules directly from the SPME surface. By use of a custom fabricated SPME fibre consisting of a stainless steel needle coated with a Linde Type A (LTA) zeolitic microporous material and low temperature plasma mass spectrometry, protonated dimethyl methylphosphonate (DMMP), diethyl ethylphosphonate (DEEP) and pinacolyl methylphosphonic acid (PinMPA) can be detected at less than 100 ppb directly in water and urine. Organophosphates were not readily detected by this approach using an uncoated needle in negative control experiments. The use of the LTA coating significantly outperformed the use of a high alumina Zeolite Socony Mobil-5 (ZSM-5) coating of comparable thickness that is significantly less polar than LTA. By conditioning the LTA probe by immersion in an aqueous CuSO4 solution, the ion abundance for protonated DMMP increased by more than 300% compared to that obtained without any conditioning. Sample recovery values were between 96 and 100% for each analyte. The detection of chemical warfare agent analogues and hydrolysis products required less than 2 min per sample. A key advantage of this sampling and ionization method is that analyte ions can be directly and rapidly sampled from chemical mixtures, such as urine and seawater, without sample preparation or chromatography for sensitive detection by mass spectrometry. This ion source should prove beneficial for portable mass spectrometry applications because relatively low detection limits can be obtained without the use of compressed gases, fluid pumps, and lasers. Moreover, the ion source is compact, can be powered with a 10 V battery, and is tolerant of complex mixtures.
Highlights
The Organization for the Prohibition of Chemical Weapons (OPCW) has mandated by the Chemical Weapon Convention to prohibit the development, production, stockpiling, transfer and use of chemical warfare agents.[1]
The effect of conditioning the Solid-phase microextraction (SPME) probes by immersion in MilliQ-grade water, aqueous 5% NaCl, or aqueous 5% CuSO4 for 1 min on the performance of low temperature plasma mass spectrometry for the detection of dimethyl methyl phosphonate is shown in Fig. S9.† The solutions containing the ionic species of CuSO4 and NaCl for conditioning the SPME fibre resulted in an ion abundance of protonated dimethyl methyl phosphonate that was 311% and 250% higher, respectively, than that for 3718 | Analyst, 2016, 141, 3714–3721
The higher density of cation-exchange sites in Linde Type A relative to that for high alumina Zeolite Socony Mobil-5 (ZSM-5) should result in more sites for the coordination and preconcentration of organophosphate analytes in zeolitic microporous materials at metal cation centres
Summary
The Organization for the Prohibition of Chemical Weapons (OPCW) has mandated by the Chemical Weapon Convention to prohibit the development, production, stockpiling, transfer and use of chemical warfare agents.[1] There are many classes of chemical warfare agents, including blister agents (mustard gas), choking agents ( phosgene), blood agents (arsines), and nerve agents The latter are synthetic organophosphate neurotoxins (e.g., Fig. 1, 1–3) that are highly potent, volatile, and colourless liquids which are challenging to detect until symptoms appear. There is a clear need to develop methods for rapidly detecting chemical warfare agents and their degradation products directly from complex mixtures in near real-time using mass spectrometry. Custom integrated SPME fibres and ionization electrodes were fabricated by coating stainless steel needles with zeolitic microporous materials Using this approach, G-series nerve agent simulants and common hydrolysis products can be rapidly extracted from. This ion source has the advantages that chemical warfare agents can be rapidly sampled and detected directly from complex mixtures, including urine, in less than 2 minutes with low limits of detection (
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