Determination of Chemical Warfare Agent Degradation Products at Low-Part-per-Billion Levels in Aqueous Samples and Sub-Part-per-Million Levels in Soils Using Capillary Electrophoresis

Abstract

A significant enhancement in the method detection limits is observed in the analysis of chemical warfare agent (CWA) degradation products in environmental samples by capillary electrophoresis (CE) using electrokinetic injection. The CE method uses indirect UV detection of the nonderivitized acidic analyte and a cationic surfactant, didodecyldimethylammonium hydroxide, for reversal of the electroosmotic flow. Analytes studied include the dibasic acid methylphosphonic acid (MPA) and its monoacid/monoalkyl esters, RMPA, where R = ethyl, isopropyl, and pinacolyl (2-(3,3-dimethylbutyl)). The CE method uses an attractive buffer system which is highly stable and inexpensive, and, in addition to reversing the electroosmotic flow, provides excellent separation efficiencies within a 3-min run. This CE method is also free from interference caused by carbonate, humic acids, and fluoride. Compared to pressure injection, electrokinetic injection with this CE buffer system provided substantially lower detection limits, up to 100-fold lower for samples in reagent water. However, to best realize the benefits of the electrokinetic injection enhancement for environmental samples, a prior cleanup of the sample using standard ion-exchange cartridges is necessary. This cleanup step uses sequential cartridges to remove sulfate (barium cartridge), chloride (silver cartridge), and cations (H+ cartridge). Using this approach, detection limits for these four acids were as low as 1-2 micrograms/L for water samples and 25-50 micrograms/L for aqueous leachates of soil samples (10 mL of leachate/1.5 g of soil). The utility of this method for separation of CWA degradation products by CE is discussed in terms of pressure injection versus electokinetic injection. The effects of voltage and time of injection on the separation were investigated. Results from three types of soils and four types of water (groundwater, artificial seawater, tap water, bay water) indicated that the method has potential for environmental monitoring. Quantitative CE analysis with electrokinetic injection enhancement of detection limits of these types of environmental samples requires the use of an appropriate internal standard approach. The data presented here indicate that an internal standard-based approach could be expected to give analysis results in the sub-part-per-million concentration range of 90-110% of the true value.

Poly(dimethylsiloxane) Microchip Electrophoresis with Contactless Conductivity Detection for Measurement of Chemical Warfare Agent Degradation Products

“…Although conventional gas chromatography, (Riches et al 2005;Pardasani et al 2006) liquid chromatography, (Liu et al 2004;D'Agostino et al 2006) capillary electrophoresis, (Nassar et al 1998(Nassar et al , 1999Rosso and Bossle 1998;Lagarrigue et al 2006) and ion chromatography (Vermillion and Crenshaw 1997;Piao et al 2005) offer high sensitivity and exquisite selectivity, they may not be suitable for use as rapid screening methods nor are they typically used for field applications because of their size and technical complexity. Due to their sensitivity, analysis speed, and portability, an intense interest has emerged in the Y.…”

Separation of thiol and cyanide hydrolysis products of chemical warfare agents by capillary electrophoresis

“…Alkyl methylphosphonic acids have been the target analytes of choice for these latter methods, as opposed to the thiols targeted in this study. CE has been used by Nassar et al [19] to quantify alkyl methylphosphonic acids in both water and soil samples. Wang et al [20] utilized a CE microchip using contactless conductivity detection to separate similar derivatives.…”

<title>Rapid chemical agent identification by surface-enhanced Raman spectroscopy</title>

“…For example, soman has a hydrolysis half-life of~2.3 hours at ambient temperatures and neutral pH, 28 and forms hydrofluoric acid (somewhat toxic) and pinacolyl methylphosphonate (relatively non-toxic). 29,30 PMP further hydrolyzes to form methyl phosphonic acid and 3,3-dimethyl-2-butanol (both non-toxic). The structural similarities between soman, PMP and MPA are expected to produce similar Raman, as well as SER spectra.…”