Optimization of Solid-Phase Extraction of a Degradation Product of Novichok (A234) and Its Application to Environmental Samples.

There have been no detailed investigations regarding solid-phase-extraction (SPE) optimization and screening for the degradation products of ethyl (1-(diethylamino)ethylidene)phosphoramidofluoridate (A234) in various environmental samples. Therefore, as a first step in the selective SPE of the degradation products of A234, we optimized the SPE adsorption and extraction parameters for the A234 degradation product ethylhydrogen (1-(diethylamino)ethylidene)phosphoramidate (cpd 1). Among various SPE cartridges, the Si cartridge (500 mg, 3 mL) selectively extracted cpd 1 using an elution volume of 4 mL of 25% H2O in acetonitrile, which eliminated most interference without cpd 1 loss during loading and washing. In addition, the sorbent capacity is also critical in the adsorption of cpd 1. The Si cartridge (500 mg, 3 mL) retained cpd 1 in the concentration range 1-10 µg/mL. The linearity of detector response of cpd 1 in deionized H2O was studied in the range of 1.0-100 ng/mL and showed good linearity with γ2 ranging from 0.9979 to 0.996. The limits of detection for cpd 1 are 10 ng/mL in the product-scan mode and 100 ng/mL in the full-scan mode. Also, after we optimized the SPE method, we validated the precision and accuracy of the Si-cartridge extraction method in real soil samples with diverse concentrations. The precision ranged from 2.5% to 5.3%. This newly developed SPE is applicable to the analysis of a degradation product of Novichok A234 in various environmental matrices, such as water, soil and sand, in the Organization for the Prohibition of Chemical Weapons (OPCW) proficiency test and unknown samples collected from suspected sites.