Determination of 1-methyl-1H-1,2,4-triazole in soils contaminated by rocket fuel using solid-phase microextraction, isotope dilution and gas chromatography–mass spectrometry

Abstract

Environmental monitoring of Central Kazakhstan territories where heavy space booster rockets land requires fast, efficient, and inexpensive analytical methods. The goal of this study was to develop a method for quantitation of the most stable transformation product of rocket fuel, i.e., highly toxic unsymmetrical dimethylhydrazine - 1-methyl-1H-1,2,4-triazole (MTA) in soils using solid-phase microextraction (SPME) in combination with gas chromatography-mass spectrometry. Quantitation of organic compounds in soil samples by SPME is complicated by a matrix effect. Thus, an isotope dilution method was chosen using deuterated analyte (1-(trideuteromethyl)-1H-1,2,4-triazole; MTA-d3) for matrix effect control. The work included study of the matrix effect, optimization of a sample equilibration stage (time and temperature) after spiking MTA-d3 and validation of the developed method. Soils of different type and water content showed an order of magnitude difference in SPME effectiveness of the analyte. Isotope dilution minimized matrix effects. However, proper equilibration of MTA-d3 in soil was required. Complete MTA-d3 equilibration at temperatures below 40°C was not observed. Increase of temperature to 60°C and 80°C enhanced equilibration reaching theoretical MTA/MTA-d3 response ratios after 13 and 3h, respectively. Recoveries of MTA depended on concentrations of spiked MTA-d3 during method validation. Lowest spiked MTA-d3 concentration (0.24 mg kg(-1)) provided best MTA recoveries (91-121%). Addition of excess water to soil sample prior to SPME increased equilibration rate, but it also decreased method sensitivity. Method detection limit depended on soil type, water content, and was always below 1 mg kg(-1). The newly developed method is fully automated, and requires much lower time, labor and financial resources compared to known methods.

Recent Applications and Newly Developed Strategies of Solid-Phase Microextraction in Contaminant Analysis: Through the Environment to Humans

“…As for commercial fibers, their use in soil analysis still has many potentials and they have been used not only in method development for new harmful contaminants [100][101][102] but rather as an analytical tool to carry out other studies, principally with ecological-environmental purposes. Indeed, given its analytical features, SPME allows for the determination of analyte free concentration and for this reason it has been used in bioavailability [103], bio-accessibility [104], and soil sorption studies involving the binding potential of dissolved organic matter (DOM) and the effects of bioremediation on contaminated industrial and agricultural soils [105,106].…”

Quantification of BTEX in Soil by Headspace SPME–GC–MS Using Combined Standard Addition and Internal Standard Calibration

“…Quantification using SA and IS calibrations requires spiking of soils with standards of analytes and an internal standard, respectively, followed by equilibration. Equilibration may be enhanced by the increase of temperature and/or addition of water [17]. The aim of this experiment was to establish time required for equilibration of spiked soils at different temperatures.…”

Perspectives and challenges of on-site quantification of organic pollutants in soils using solid-phase microextraction

“…Because of so many affecting factors, extraction effectiveness of analytes from different soils may easily vary by an order of magnitude [36]. This makes quantification of organic compounds using a simple external standard approach inaccurate.…”

“…The magnitude of a matrix effect depends on analyte properties, the most important of which are: a) hydrophobicity, b) volatility, c) acidity/basicity. For example, an increase of a water content in soil increases the SPME effectiveness for hydrophobic compounds while polar compounds become stronger retained by wet soil [20,36].…”