Efficient Extraction of Sulfur and Nitrogen Mustards from Nonpolar Matrix and an Investigation on Their Sorption Behavior on Silica

Extraction of vesicant class of chemical warfare agents (CWAs) such as sulfur mustard and nitrogen mustards from the environmental matrices is of prime importance, from a forensic and verification viewpoint of the Chemical Weapons Convention (CWC). For extraction of Convention Related Compounds from nonpolar organic medium, commercially available silica cartridges are used extensively, but silica cartridges exhibit limited efficiency toward vesicant classes of compounds. It is expected that sulfur mustard being nonpolar does not retain sufficiently on silica surface, and nitrogen mustards (being basic) are strongly adsorbed on acidic silica surface, resulting in their poor recoveries. Contrary to the expected higher recovery of sulfur mustard over nitrogen mustards, it was observed that the recovery of sulfur mustard was lower than that of nitrogen mustards with the silica based sorbent. The reason for this typical behavior of these agents on silica was investigated. This study was aimed to develop an analytical method for efficient extraction and enrichment of sulfur and nitrogen mustards from hydrophobic matrices. In this work, the polymeric sorbent was synthesized with polar methacrylic acid (MAA) as monomer and ethylene glycol dimethacrylate (EGDMA) as cross-linker and used for solid phase extraction (SPE) of sulfur mustard and nitrogen mustards. The extraction efficiency of the polymeric sorbent was optimized and compared with that of silica cartridges. Both classes of analytes were recovered in good amounts from the polymeric sorbent compared to silica. The extraction parameters were optimized for the proposed method which included extraction solvent ethyl acetate and washing solvent <i>n</i>-hexane (1 mL). The recoveries of the analytes ranged from 75 to 87% with relative standard deviations (RSDs) lower than 9%. The limit of detection (LOD) was found to be in the range of 0.075–0.150 μg mL^–1, and limit of quantification (LOQ) was >0.25 μg mL^–1. The linear dynamic range of optimized method was found to be 0.50–20 μg mL^–1 (<i>r</i>² = 0.9994) for sulfur mustard and 0.25–20 μg mL^–1 (<i>r</i>² = 0.9897–0.9987) for nitrogen mustards, respectively