Separation and detection of VX and its methylphosphonic acid degradation products on a microchip using indirect laser-induced fluorescence

Abstract

The application of indirect LIF (IDLIF) technique for on-chip electrophoretic separation and detection of the nerve agent O-ethyl S-[2-(diisopropylamino)ethyl] methylphosphonothiolate (VX) and its major phosphonic degradation products, ethyl methylphosphonic acid (EMPA) and methylphosphonic acid (MPA) was demonstrated. Separation and detection of MPA degradation products of VX and the nerve agent isopropyl methylphosphonofluoridate (GB) are presented. The negatively charged dye eosin was found to be a good fluorescent marker for both the negatively charged phosphonic acids and the positively charged VX, and was chosen as the IDLIF visualization fluorescent dye. Separation and detection of VX, EMPA, and MPA in a simple-cross microchip were completed within less than a minute, and consumed only a 50 pL sample volume. A characteristic system peak that appeared in all IDLIF electropherograms served as an internal standard that increased the reliability of peak identification. The negative peak of both VX and the MPAs is in agreement with indirect detection theory and with previous reports in the literature. The LOD of VX and EMPA by IDLIF was 30 and 37 microM, respectively. Despite the fact that the detection sensitivity is relatively low, the rapid simultaneous on-chip analysis of both VX and its degradation products as well as the separation and detection of the MPA degradation products of both VX and GB, increases detection reliability and may present a choice when sensitivity is not critical compared with speed and simplicity of the assay.

In situ determination of nerve agents in various matrices by portable capillary electropherograph with contactless conductivity detection

“…4B) appears at approximately 83 seconds for all matrices contaminated with VX. Heleg-Shabtai et al [25] have separated VX and its degradation products (EMPA) by CE using a 1 mM carbonate background electrolyte at pH 7.7 with LIF detection. As the pKa of VX is high (the values given in the literature range between 8.6 and 9.4) [58,59], the undegraded VX migrated ahead of the EOF as a cationic peak in their electrolyte system at pH 7.7.…”

“…Of the approximately 40 publications in which the use of capillary electrophoresis for the detection of CWA is reported, only three applied it for the determination of genuine nerve agents [25,33,34] rather than their simulants or degradation products. The analyses were conducted in the laboratory, not in the field.…”

“…The prevailing CE detection methods are UV and conductivity detection, but laserinduced fluorescence [22][23][24][25], MS [26][27][28][29] and element specific detectors [30,31] have also been used. CE separation with indirect UV detection of NA degradation products was first described by Pianetti et al in 1993 [32].…”

Identification of chemical warfare agents using a portable microchip-based detection device

“…Not enough information is available about detection of real CWA. Of the approximately 40 publications in which the use of capillary electrophoresis for the detection of CWA is reported, only three reported detection of genuine nerve agents [1,2,18] rather than their simulants or degradation products. The present work, to the best of our knowledge, reports the first portable, microchip electrophoresis and CCD based, device for detection of real CWA and their degradation products.…”

Rapid and Efficient Filtration-Based Procedure for Separation and Safe Analysis of CBRN Mixed Samples

“…Ethyl methylphosphnic acid (EMPA) and pinacolyl methylphophonic acid (PMPA) are the products of the spontaneous hydrolysis of the chemical warfare agents (CWA) VX and GD (soman), respectively. They were used as surrogates for the corresponding chemical warfare agents [11]–[13].…”