CE–MS-MS for the Identification of Chemical Warfare Agent Degradation Products

Please direct correspondence to Pierre Gareil at [email protected]. he different conflicts of the 20th century were marked by the use of chemical weapons. Therefore, the Chemical Weapons Convention (CWC) was signed in 1993 and came into force in 1997 to prohibit the development, production, stockpiling, and use of chemical warfare agents (1). But today, the use of chemical weapons by terrorist organizations represents a great threat. Thus, the development of analytical techniques for the detection and identification of chemical warfare agents has become essential. Chemical weapons are divided into four groups: vesicant (mustard gas), nerve (tabun, sarin, soman, VX, and so forth), blood (hydrogen cyanide), and incapacitating agents. Nerve agents, which are the most lethal chemicals, generally are hydrolyzed over time to first produce alkyl alkylphosphonic acids and then alkylphosphonic acids (Figure 1a) that can be used to identify the present nerve agent. Gas chromatography (GC) has been used widely for the detection of nerve agents but the analysis of their degradation products, which are less volatile and more polar, requires a timeconsuming chemical derivatization (2). Liquid chromatography (LC) avoids the derivatization of the degradation products but very polar compounds generally are separated with more difficulty in the most commonly used reversed-phase mode. Capillary electrophoresis (CE) represents an interesting alternative technique for the analysis of nerve agent degradation products because CE intrinsically allows the separation of charged or polar species. Moreover, CE is known to provide high separation efficiency thanks to the flat profile of the electroosmotic flow through the capillary. Sample consumption is very limited with typical sample injection volumes between 1 and 20 nL. Therefore, CE with indirect UV detection has been The terrorist threat has encouraged the development of analytical techniques for the detection and identification of chemical warfare agent degradation products. Capillary electrophoresis (CE) presents interesting features such as high separation efficiency, low sample consumption, and electrophoretic separation principles that are very complementary to those of the most commonly used chromatographic techniques. Its hyphenation with mass spectrometry (CE–MS) provides very powerful identification capabilities, explaining the growing interest in CE–MS for a wide range of applications. A CE–MS method was thus developed in this work for the identification of phosphonic acids present in deionized water and soil extracts. CE–MS-MS appeared to be a particularly efficient tool for the identification of isomeric alkyl alkylphosphonic acids. Moreover, analytes can be easily preconcentrated in-capillary by using field-amplified sample stacking to enhance sensitivity in low-conductivity matrices.