Extraction of Novichoks from aqueous samples for verification analysis of Chemical Weapons Convention

Abstract

ABSTRACT The study was undertaken with the objective of evaluating the different procedures for the extraction of the Novichok class of chemicals from aqueous samples for the verification of Chemical Weapons Convention (CWC). These classes of chemicals are recently added to the scheduled list of CWC, which necessitates the optimisation of analytical protocols for their verification analyses in different environmental samples. Three analytes, namely N-(1-(diethylamino)ethylidene)-P-methylphosphonamidic fluoride (A230), methyl N-(1-(diethylamino)ethylidene)phosphoramidofluoridate (A232) and ethyl N-(1-(diethylamino)ethylidene)phosphoramidofluoridate (A234), were taken as representative chemicals in aqueous samples and extracted with established protocols, such as liquid–liquid extraction (LLE), solid phase extraction (SPE), solid-supported liquid extraction (SLE) and liquid phase microextraction (LPME) techniques. The extraction efficacies were evaluated in terms of the recoveries of analytes as well as the removal of background interferences. Amongst the extraction techniques, SLE offered the least (43.2–66.7%) and LLE and SPE-HLB offered the best recoveries (79.1–92.9%) of the analytes with adequate sample clean-up. LPME techniques produced much better detection limits, going down to 7.6 ng/mL for A234. LPME methods were also found advantageous in terms of high enrichment factors, ease of operation, minimal waste generation and individual safety for handling the toxic chemicals.