Determination of Lewisites and their hydrolysis products in aqueous and multiphase samples by in-sorbent tube butyl thiolation followed by thermal desorption–gas chromatography–full scan mass spectrometry

• Method for determination of Lewisites and their hydrolysis products is developed.
• Rapid and efficient preparation of aqueous and multiphase liquid samples.
• A tube packed with glass wool and solid adsorbent utilised for the preparation.
• In-tube derivatisation and direct thermal desorption into a gas chromatography inlet.
• Full scan mass spectrometry was used for trace analyte identification.

A rapid, sensitive and robust method for determining the chemical warfare agents Lewisites and their hydrolysis products in aqueous and multiphase sample matrices has been developed as an extension of the previous work (Terzic, 2010 [32]). In the new method, the acidification of the sample and use of 1-butanethiol derivatisation instead of trimethylsilylation significantly improved both, qualitative and quantitative aspects of targeted analysis of Lewisite species. The limit of detection was ≤100 ng/ml in full scan MS, with sample volume of 10 μl only. The whole sample preparation procedure took 9 min, while the gas chromatography (GC)–mass spectrometry (MS) analysis cycle was under 22 min. The method deals efficiently with the multiphase sample matrices offering a fast and simple alternative to the conventional approach of liquid–liquid extraction combined with derivatisation. Multiphase sample matrices can be encountered or formed when preparing environmental, industrial, waste or decontamination waste samples for a GC–MS analysis. The applicability and robustness of the method were demonstrated by the successful analysis of 11 years old OPCW Official Proficiency Test sample and a triphase liquid sample. The same equipment set-up, tubes and derivatising agent have been used for collection, preparation and analysis of Lewisites in air samples (Terzic et al., 2012 [35]). The minimal logistic requirements, ease of operation, versatility and other features aforementioned, make this method an excellent choice for an environmental or forensic field laboratory.