Fast Determination of 1-Methyl-1H-1,2,4-triazole in Soils Contaminated by Rocket Fuel Using Solvent Extraction, Isotope Dilution and GC–MS

1-Methyl-1H-1,2,4-triazole (MTA) is the most stable and abundant transformation product of dimethylhydrazine-based rocket fuel. Concentrations of MTA in soils affected by rocket fuel spills are regularly monitored using a number of available methods mainly based on GC–MS. Complex, time and labor intensive sample preparation makes quantification of MTA quite costly and unsuitable for on-site measurements. The goal of this study was to develop a new method for fast determination of MTA in soil samples based on solvent extraction and GC–MS. MTA extraction effectiveness using known polar organic solvents varies from 30 to 95 % for different soils. Isotope dilution method involving (1-trideuteromethyl)-1H-1,2,4-triazole (MTA-d3) provides efficient matrix effect control and analyte recovery in the range of 70–130 % for all tested solvents—acetone, methanol and acetonitrile. Any of the tested solvents may be used for the method depending on their affordability and accessibility in the lab. Addition of 3 g of 4Å molecular sieves to acetone extracts from soils removes 98 % of water and does not affect MTA/MTA-d3 concentrations ratio. Compared to the competitive SPME-based method, the developed approach does not require long-time equilibration of soils at elevated temperatures. The developed method is more suitable for determination of concentration at a level above 300 mg kg⁻¹. MTA concentration in soils taken from the site of accidental “Proton” rocket crash in 2013 reached 600 mg kg⁻¹. According to the method validation, its reproducibility and accuracy are below 9 and 23 %, respectively. Detection limit is below 2 mg kg⁻¹ for all studied samples.