Quantification of transformation products of rocket fuel unsymmetrical dimethylhydrazine in soils using SPME and GC-MS

Analysis of nitrogen-containing rocket fuel transformation products in loamy soil by thermal desorption gas chromatography-tandem mass spectrometry

Unsymmetrical dimethylhydrazine (UDMH) based rocket fuel, when released into the soil, undergoes oxidative transformations to form a variety of toxic nitrogen-containing products (TPs). Loamy soils containing aluminosilicates (clay) are capable of strong binding and retention of UDMH TPs due to a combination of polar sorption and cation-exchange properties, posing challenges for their extraction and quantification. To overcome this problem, the present study proposes direct thermal desorption (TD) of analytes from loam facilitated by the addition of modifiers competing with UDMH TPs for sorption centers and ensuring their conversion into molecular form. Among tested additives, the mixture of potassium chloride and hydroxide demonstrated the best performance and provided recoveries of the most UDMH TPs exceeding 70% under optimized TD conditions (200°C, 30 min). The online combination of TD with gas chromatography-tandem mass spectrometry allowed for the development of a method for the determination of 15 UDMH TPs in loamy soils with limits of detection in the range of 0.2-15 µg/kg. The use of matrix-matched calibration and deuterated internal standards ensured high accuracy (80%-100%) and precision (relative standard deviation < 18%) of the analysis. The developed method was validated and successfully tested in the analyses of real loamy soil samples polluted with rocket fuel.

Optimization of headspace solid-phase microextraction of volatile organic compounds from dry soil samples by porous coatings using COMSOL Multiphysics

Headspace solid-phase microextraction (HSSPME) is one of the simplest and cost-efficient sample preparation approaches for determination of volatile organic compounds (VOCs) in soil. This study was aimed at the development of the model for numerical optimization of HSSPME of volatile organic compounds from dry soil samples by porous coatings using COMSOL Multiphysics (CMP). ‘Transport of Diluted Species in Porous Medium’ physics was used for modeling. Effect of sample mass, pressure, fiber-headspace and soil-headspace distribution constants on extraction profiles and time of 95% equilibrium has been studied using the developed model. Equilibrium extraction under atmospheric pressure (1 atm) can take up to 97 min, while under vacuum (0.0313 atm) – 2.3 min. Equilibration time under vacuum was 42-43 times lower than under 1 atm at all studied distribution constants and sample masses. The developed model was modified for optimization of pre-incubation time using ‘Transport of Diluted Species’ physics. According to the obtained plots, 95% equilibration time can reach 13.3 min and depends on both sample mass and soil-headspace distribution constant of the analyte. The developed model can be recommended for optimization of pressure, preincubation and extraction time when fiber-headspace and soil-headspace distribution constants, soil porosity and density are known.

Unsymmetrical dimethylhydrazine and related compounds in the environment: Recent updates on pretreatment, analysis, and removal techniques

Unsymmetrical dimethylhydrazine (1,1-Dimethylhydrazine, UDMH) has been widely used as aerospace fuel in many countries. The launch of space vehicles can cause the release and leakage of UDMH into the environment, posing serious threats to ecology system and human population. Even worse, the health risks are also pertinent to its numerous classes of transformation products including N-Nitrosodimethylamine (NDMA), because most of them display carcinogenic and mutagenic properties. Recently, there has been an intense ongoing development of simple, fast, green, and effective techniques for determining and removing these hazardous substances. This review summarizes the latest research progress regarding the sources, fates, pretreatment, analysis, and removal techniques of UDMH and related products in the environment. Sample preparation methods mainly include pressurized liquid extraction, liquid-phase microextraction techniques, solid-phase extraction, headspace-solid-phase microextraction, and supercritical fluid extraction. Detection and identification methods mainly include high-performance liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS), gas chromatography coupled with tandem mass spectrometry (GC-MS/MS), and sensors. Removal methods mainly include advanced oxidation processes, adsorption, biodegradation techniques. The advantages/disadvantages, applications, and trends of the proposed approaches are thoroughly discussed to provide a valuable reference for further studies.

Quantification of trace transformation products of rocket fuel unsymmetrical dimethylhydrazine in sand using vacuum-assisted headspace solid-phase microextraction

Quantification of unsymmetrical dimethylhydrazine transformation products in solid samples is an important stage in monitoring of environmental pollution caused by heavy rockets launches. The new method for simultaneous quantification of unsymmetrical dimethylhydrazine transformation products in sand samples using vacuum-assisted headspace solid-phase microextraction without addition of water followed by gas chromatography-mass spectrometry is proposed. Decreasing air evacuation time from 120 to 20 s at 23 °C resulted in increased responses of analytes by 25-46% and allowed obtaining similar responses as after evacuation at -30 °C. The best combination of responses of analytes and their relative standard deviations (RSDs) was achieved after air evacuation of a sample (m = 1.00 g) for 20 s at 23 °C, incubation for 30 min at 40 °C, and 30-min extraction at 40 °C by Carboxen/polydimethylsiloxane (Car/PDMS) fiber. The method was validated in terms of linearity (R²=0.9912-0.9938), limits of detection (0.035 to 3.6 ng g^-1), limits of quantification (0.12-12 ng g^-1), recovery (84-97% with RSDs 1-11%), repeatability (RSDs 3-9%), and reproducibility (RSDs 7-11%). It has a number of major advantages over existing methods based on headspace solid-phase microextraction-lower detection limits, better accuracy and precision at similar or lower cost of sample preparation. The developed method was successfully applied for studying losses of analytes from open vials with model sand spiked with unsymmetrical dimethylhydrazine transformation products. It can be recommended for analysis of trace concentrations of unsymmetrical dimethylhydrazine transformation products when studying their transformation, migration and distribution in contaminated sand.

The 'burn' of ranitidine recall: current insights and mitigation strategies

Ranitidine was one of the most commonly used medications for the treatment of gastroesophageal reflux disease. On 1 April 2020, the US Food and Drug Administration requested all manufacturers to immediately withdraw ranitidine from the market because of concern of higher than acceptable levels of N-nitrosodimethylamine, a potential carcinogen. Herein, we highlight the reason for this recall, along with the effects of this recall on both the patients and healthcare practitioners, and offer insights on management strategies.

Quantification of transformation products of rocket fuel unsymmetrical dimethylhydrazine in air using solid-phase microextraction

Quantification of unsymmetrical dimethylhydrazine transformation products in ambient air is important for assessing the environmental impact of heavy rocket launches. There are very little data of such analyses, which is mainly caused by the low number of analytes covered by the available analytical methods and their complexity. A simple and cost-efficient method for accurate simultaneous determination of seven unsymmetrical dimethylhydrazine transformation products in air using solid-phase microextraction followed by gas chromatography-mass spectrometry was developed. The method was optimized for air sampling and solid-phase microextraction from 20-mL vials, which allows full automation of analysis. The extraction for 5 min by Carboxen/polydimethylsiloxane fiber from amber vials and desorption for 3 min provided the greatest analytes' responses, lowest relative standard deviations, linear calibration (R² ≥ 0.99), and limits of detection from 0.12 to 0.5 μg/m³ . Samples with concentrations 500 μg/m³ can be stored at 21 ± 1°C without substantial losses (1-11%) for up to 24 h, while air samples with concentrations 10 and 50 μg/m³ stored for up to 24 h can be used for accurate quantification of only two and four out of seven analytes, respectively. The developed method was successfully tested for the analysis of air above real soil samples contaminated with unsymmetrical dimethylhydrazine rocket fuel.

Determination of phase-partitioning tracer candidates in production waters from oilfields based on solid-phase microextraction followed by gas chromatography-tandem mass spectrometry

In the present document, we report the development of an analytical method consisting of a sequential direct-immersion/headspace solid-phase microextraction (DI-HS-SPME) followed by gas-phase chromatography and tandem mass spectrometry (GC-MS/MS) for simultaneous analysis of 4-chlorobenzyl alcohol, 2,6-dichlorobenzyl alcohol, 4-methoxybenzyl alcohol, 3,4-dimethoxybenzyl alcohol, pyridine, and 2,3-dimethylpyrazine in oilfield production waters. These compounds are under evaluation for use as phase-partitioning tracers in oil reservoirs. To the best of our knowledge, this is the first time SPME has been applied to the analysis of these compounds in production waters, or any other type of matrix where the compounds targeted are the base for a technical application. Relevant extraction parameters, such as the adsorbent phase of the fiber, direct immersion or headspace, addition of salt, temperature and time of extraction were investigated. The final optimal operation conditions consist on extracting 5 mL of sample at pH 9.0 with 1.8 g of NaCl with constant stirring during 5 minutes of DI-SPME followed by 15 minutes of HS-SPME at 70 °C using a DVB/CAR/PDMS (50/30 µm) fiber. The limits of quantification (LOQ), linearity, precision and accuracy of the method were evaluated. Analyses of the tracer compounds and recovery studies were also performed on production waters from 8 different oilfields of the Norwegian continental shelf. LOQs between 0.080 and 0.35 µg L^-1 were obtained. The recovery yields of the method were consistently higher than 85% and RSDs less than 13%. None of the tracer compounds was found in the real samples processed, which is consistent with one of the requirements for an artificial tracer in an oilfield: absence or constant and low background in the traced fluid. The performance of the method developed, combined with its easiness to automate, introduce a new, accurate and cost-efficient technique to process the hundreds of samples required by an inter-well tracer test.

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

The present review aims to describe the recent and most impactful applications in pollutant analysis using solid-phase microextraction (SPME) technology in environmental, food, and bio-clinical analysis. The covered papers were published in the last 5 years (2014–2019) thus providing the reader with information about the current state-of-the-art and the future potential directions of the research in pollutant monitoring using SPME. To this end, we revised the studies focused on the investigation of persistent organic pollutants (POPs), pesticides, and emerging pollutants (EPs) including personal care products (PPCPs), in different environmental, food, and bio-clinical matrices. We especially emphasized the role that SPME is having in contaminant surveys following the path that goes from the environment to humans passing through the food web. Besides, this review covers the last technological developments encompassing the use of novel extraction coatings (e.g., metal-organic frameworks, covalent organic frameworks, PDMS-overcoated fiber), geometries (e.g., Arrow-SPME, multiple monolithic fiber-SPME), approaches (e.g., vacuum and cold fiber SPME), and on-site devices. The applications of SPME hyphenated with ambient mass spectrometry have also been described.

Reversible photochromic photocatalyst Bi2O3/TiO2/Al2O3 with enhanced visible photoactivity: application toward UDMH degradation in wastewater

1,1-Dimethylhydrazine (UDMH) and its by-products were considered carcinogenic toxins and represent a serious health hazard to the population once present in water under natural conditions without treatment. The conventional degradation method suffers from incomplete removal of intermediate products (especially N-nitrosodimethylamine (NDMA)), the powdery catalysis being difficult to recover and results in high energy consumption. In this study, a series of Bi₂O₃/TiO₂/Al₂O₃ (BTA) photocatalysts have been successfully synthesized by a simple dry mixing method with powder material followed by their immobilization. It was evaluated by the photocatalytic degradation of UDMH present in wastewater, which can be recovered by rapid filtration and utilizes only solar energy. The catalyst exhibited markedly enhanced photocatalytic activity for the degradation of UDMH wastewater compared with conventional TiO₂/Al₂O₃ (TA) catalysts under UV, visible and solar irradiation. Besides, the intermediate NDMA was gradually completely degraded. The photocatalysts were extensively characterized using scanning electron microscopy, energy dispersive spectrometry, specific surface area (BET), X-ray diffraction, X-ray photoelectron spectroscopy, UV-visible diffuse reflectance spectroscopy and photo-electrochemical I-t curves evaluation. The results revealed that all the BTA composites exhibited high stability and stronger absorbance in visible light. In addition, the BTA exhibited a reversible photochromic property that can effectively expand the range of light absorption and enhance the photocatalytic activity. The reversible photochromic properties of BTA explained in the proposed mechanism model are expected to be useful for detecting and sensing UDMH or other organic contaminants.

Investigation on the compositions of unsymmetrical dimethylhydrazine treatment with different oxidants using solid-phase micro-extraction-gas chromatography-mass spectrometer

The majority of unsymmetrical dimethylhydrazine (UDMH) treatments produce lots of toxic by-products, among which N-Nitrosodimethylamine (NDMA) is a strong carcinogen. The compositions of the by-products are important for evaluating the treatment efficiency and understanding the UDMH degradation mechanism to achieve UDMH mineralization. The intermediate and end products of UDMH treatment with different oxidants were investigated by using a simple and fast method, solid-phase micro-extraction (SPME) in combination with gas chromatography-mass spectrometry (GC-MS). The effects of several parameters (coating fibre, salt addition, pH, sampling time and desorption time) were studied to optimize analyte recovery. The best response can be attained by the 65 µm PDMS/DVB fibre at pH 7 during 10 min after desorption of 1 min in the GC inlet. The intermediate and final oxidative products of UDMH wastewater treatment with different oxidants (O₃, Mn²⁺/O₃, Fe²⁺/H₂O₂) were investigated. The results showed that the UDMH treatment with O₃ could lead to high yields of NDMA. Metal catalytic ozonation could largely minimize the formation of NDMA. No NDMA was observed in the final decontaminated samples after treatment with Fe²⁺/H₂O₂. The NDMA formation and degradation mechanism were discussed based on the intermediates. This study is expected to provide useful information for controlling NDMA formation during UDMH wastewater treatment.

Quantification of transformation products of unsymmetrical dimethylhydrazine in aqueous extracts from soil based on vacuum-assisted headspace solid-phase microextraction

Quantification of transformation products of unsymmetrical dimethylhydrazine (UDMH) in soil requires tedious, time- and labor-consuming sample preparation. The simple and fast method for quantification of transformation products of UDMH in aqueous extracts from soil using vacuum-assisted headspace solid-phase microextraction (Vac-HSSPME) was optimized in this work. The method is based on extraction of analytes from soil with water followed by Vac-HSSPME of the obtained aqueous extracts, and gas chromatography-mass spectrometry analysis. The target transformation products were: pyrazine, 1-methyl-1H-pyrazole, N-nitrosodimethylamine, N,N-dimethylformamide, 1-methyl-1Н-1,2,4-triazole, 1-methyl-imidazole and 1H-pyrazole. The effect of a sample pH on responses of target analytes was studied. It was negligible, and no pH adjustment was recommended before a subsequent extraction. The water amount was optimized to provide the best combination of analytes responses and their precision. Extraction by adding 7.00 mL of water to 2.0 g of soil ensured linear dependence of responses of the analytes on their concentrations in soil. The optimized method provided detection limits of target analytes in soil in the range from 0.2 to 9 ng/g. The spike recoveries obtained for model samples were in the range 90-103%. The developed method can be recommended for application in laboratories conducting routine analyses of soil samples potentially contaminated by rocket fuel residuals.