Overcoming the BSTFA: Study on Trimethylsilylation Derivatization Procedures for Chemical Weapons Convention-Related Alcohols in Field Analysis

Abstract

After the use of chemical weapons, there is a gradual spontaneous decomposition of chemical warfare agents (CWAs), and only degradation products can be present at the time of sample collection. Depending on the type of parent compound, these are most often acids, alcohols, or thiols. This article deals with the development and optimization of methods for the trimethylsilylation of controlled alcohols that outperforms the currently widely used method with N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) prior to gas chromatographic identification. Thiodiglycol (TDG) was chosen as a model alcohol for the development and optimization of methods. Nine trimethylsilylating agents were tested as derivatization agents. For each reagent, the method was optimized in terms of reaction medium (seven tested solvents), reaction time, and temperature. The temporal stability of the resulting derivatives and the effect of the addition of the reaction catalyst were also monitored. Subsequently, optimal methods were applied in the derivatization of N-ethyldiethanolamine, N-methyldiethanolamine, triethanolamine, 2-diisopropylaminoethanol (DIAE), and 3-quinuclidinol. The developed methods were compared in all monitored properties with the standard BSTFA-method (in acetonitrile for 30 min at 60 °C). From the developed methods, three were selected that showed similar or better sensitivity parameters than BSTFA, and at the same time were less demanding to perform. Trimethylsilylation via trimethylsilyl cyanide (TMSCN) appears to be the most successful method. In conclusion, the selected methods were applied in the analysis of contaminated environmental and urban samples – sand, acrylic paint, asphalt-aluminum paint, and concrete. The samples were measured on both a benchtop and a field gas chromatograph.