Journal of Chromatography A, 1076 (2005) 27–33 On-matrix derivatisation–extraction of precursors of nitrogen- and sulfur-mustards for verification of chemical weapons convention D.K. Dubey a,∗ , Deepak Pardasani a , Meehir Palit a , A.K. Gupta a , Rajiv Jain b a Vertox Laboratory, Defence Research and Development Establishment, Jhansi Road, Gwalior, MP 474002, India b School of Studies in Chemistry, Jiwaji University, Gwalior, India Received 17 April 2005; received in revised form 17 April 2005; accepted 18 April 2005 Abstract Development and refinement of sample preparation protocols for retrospective detection and identification of chemical warfare agents (CWAs) and their markers is of paramount importance from verification point of view of chemical weapons convention (CWC). Precursors of nitrogen- and sulfur-mustards (NMPs and SMPs) are polar adsorptive markers of vesicant class of CWAs. Their detection in a given environmental sample may imply past contamination with mustards. For the efficient extraction of NMPs and SMPs from soil, on-matrix derivatisation–extraction (OMDEX) method was developed and optimized. The method involved trifluoroacetylation of analytes on soil itself, followed by extraction with suitable solvent. The extracted samples were analyzed by gas chromatography–mass spectrometry (GC–MS). This virtually single-step sample preparation offered better recoveries of NMPs and SMPs in comparison to conventionally used extraction, evaporation and derivatisation. The best recoveries of analytes were obtained with acetonitrile by OMDEX method. Dynamic linearity range of trifluoroacetylated (TFA) derivatives of NMPs and SMPs was 1–12 g/L in GC–MS analysis in SIM mode. Repeatability and reproducibility of this technique containing 5 and 10 g analytes/gm soil was <3.3% and <4.6%, respectively. OMDEX technique was finally applied for the detection of TFA derivatives of NMPs in the soil sample supplied in 16th official proficiency test conducted by OPCW in October 2004. © 2005 Elsevier B.V. All rights reserved. Keywords: Nitrogen mustard; Sulfur mustard; Chemical weapons convention; Verification; Derivatisation; Extraction 1. Introduction The development of efficient analytical procedures for chemical warfare agents (CWAs) and their characteristic degradation compounds is an important area of contemporary research [1–5]. The methods aiming for extraction, detection and identification of CWAs and related compounds are crucial (i) to identify and monitor cleanup of contaminated area and (ii) to verify the compliance or non-compliance of chemical weapons convention (CWC). The CWC came in existence in April 1997 with the objective of prohibition on proliferation of CWAs [6,7]. The treaty is administered by the Organiza- tion for Prohibition of Chemical Weapons (OPCW), through its strict verification regime [6–8]. Verification involves inspection of declared and suspected chemical weapons ∗ Corresponding author. Tel.: +91 751 2233488; fax: +91 751 2341148. E-mail address: dkdubey@rediffmail.com (D.K. Dubey). (CW) facilities. Environmental samples such as soil, water, vegetation etc are collected from these facilities and sub- jected to unequivocal identification of convention-related compounds (CRCs), which includes CWAs, their analogues, precursors and characteristic degradation compounds (so called signatures/markers). The CRCs are included in three schedules of CWC based on their potential risk to the convention [6,7]. The analysis of collected samples is generally performed on-site by the inspectors. In case of any ambiguity, the sam- ples are sent to designated laboratories appointed by the OPCW for unequivocal identification of CRCs [8–12]. The OPCW maintains a network of designated laboratories by periodically evaluating their analytical capabilities through official proficiency tests (OPTs) [9–11]. The analytical procedure of CRCs in environmental ma- trices involves four major steps: (i) extraction (ii) concentra- tion (iii) derivatisation and (iv) identification [12]. First three 0021-9673/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.chroma.2005.04.066