D. S. Kosyakov

Simultaneous determination of 1,1-dimethylhydrazine and products of its oxidative transformations by liquid chromatography–tandem mass spectrometry

A liquid chromatography–tandem mass spectrometry method is proposed for the simultaneous determination of 1,1-dimethylhydrazine, methylhydrazine, N,N-dimethylformamide, 1-methyl-1H-1,2,4-triazole, dimethylguanidine, N-nitrosodimethylamine and 1,1,4,4-tetramethyltetrazene, important rocket fuel pollutants of soils. Chromatographic separation was conducted according to previously published results in an isocratic mode on an analytical column with a Nucleosil-100–5SA sulfo-cation-exchanger. The mobile phase composition was optimised in order to achieve effective separation of all analytes and provide high sensitivity of mass spectrometric detection – an ammonium acetate buffer solution (50 mM, pH 5.4) containing methanol (25%) was used. Detection was performed in the positive electrospray ionisation mode with multiple reaction monitoring (MRM). The parameters of ion source, ion optics, the inlet potentials of the quadrupoles and the collision energy for the detection of the found product ions were optimised. Calibration dependences for all compounds are linear in wide concentration ranges, covering 3–4 orders of magnitude. The detection limits vary from 40 pg mL−1 for dimethylguanidine to 18 ng mL−1 for methylhydrazine. No significant matrix effects were observed in the analysis of acid peaty soil extracts. The method was validated and successfully used to analyse a real soil sample collected at the place of impact of the first stage of a carrier rocket.

Spectrophotometric determination of hydrazine, methylhydrazine, and 1,1-dimethylhydrazine with preliminary derivatization by 5-nitro-2-furaldehyde

Abstract5-Nitro-2-furaldehyde, a new derivatizing agent for the spectrophotometric determination of hydrazine, methylhydrazine, and 1,1-dimethylhydrazine is proposed. It is characterized by high solubility in water and by a substantial difference in the positions of absorption bands of the formed colored derivatives. The kinetics of the reaction of analyte derivatization is studied, and reaction conditions (pH 5, concentration of derivatizing agent 2 mM, 60° C, duration 40 min) are optimized. The limits of detection are 5, 3, and 1.5 μg/L for hydrazine, methylhydrazine, and 1,1-dimetlhydrazine, respectively. A possibility of the spectrophotometric determination of analytes in their simultaneous presence using the Firordt method is shown. The developed approach is successfully applied to the analysis of polluted peat bog soil selected at a place of impact of the first step of a carrier rocket.

Determination of transformation products of 1,1-dimethylhydrazine by gas chromatography–tandem mass spectrometry

A method is proposed for the highly sensitive simultaneous determination of eight major products of oxidative transformations of 1,1-dimethylhydrazine, widely used as a rocket fuel (formaldehyde dimethylhydrazone, acetaldehyde dimethylhydrazone, 2-furaldehyde dimethylhydrazone, 1,1,4,4-tetramethyl-2-tetrazene, N,N-dimethylformamide, N-nitrosodimethylamine, 1-methyl-1H-1,2,4-triazole and 1-formyl-2,2dimethylhydrazine) by gas chromatography–tandem mass spectrometry. The detection parameters in the MRM mode are optimized. The conditions for the efficient separation of analytes on an HP-INNOWAX polar stationary phase are chosen. The detection limits achieved are in the range 0.3–2.3 ng/mL, which is 1?2 orders of magnitude lower than those for the GC/MS method. The developed approaches are tested in the analysis of real samples, surface water of peaty swamp with high contents of organic substance taken at the place of impact of the first rocket stage. It is found that N,N-dimethylformamide and 1-methyl-1H-1,2,4-triazole are predominant among the studied transformation products in natural waters. The results obtained are of great importance for the assessment of the environmental impacts of space rocket activities.

Characterisation of oxidation products of 1,1-dimethylhydrazine by high-resolution orbitrap mass spectrometry

1,1-Dimethylhydrazine is used as a fuel for carrier rockets in the majority of countries implementing space exploration programs. Being highly reactive, 1,1-dimethylhydrazine easily undergoes oxidative transformation with the formation of a number of toxic, mutagenic, and teratogenic compounds. The use of high-resolution mass spectrometry for the study of the reaction of 1,1-dimethylhydrazine oxidation with hydrogen peroxide in aqueous solution allowed us to find hundreds of nitrogen-containing products of the CHN and CHNO classes, formed via radical processes. The vast majority of the compounds have not been previously considered as possible products of the transformation of rocket fuel. We have shown that the oxidation of 1,1-dimethylhydrazine proceeds in two stages, with the formation of a great number of complex unstable intermediates that contain up to ten nitrogen atoms. These intermediates are subsequently converted into final reaction products with a concomitant decrease in the average molecular weight. The intermediates and final products of the oxidative transformation of 1,1-dimethylhydrazine were characterised on the basis of their elemental composition using van Krevelen diagrams and possible compounds corresponding to the most intense peaks in the mass spectra were proposed. The data obtained are indicative of the presence of the following classes of heterocyclic nitrogen-containing compounds among the oxidation products: imines, piperidines, pyrrolidines, dihydropyrazoles, dihydroimidazoles, triazoles, aminotriazines, and tetrazines. The results obtained open up possibilities for the targeted search and identification of new toxic products of the degradation of rocket fuel and, as a result, a more adequate assessment of the ecological consequences of space-rocket activity.

Optimization of sample preparation conditions in the study of lignin by MALDI mass spectrometry

In this study we compared the efficiencies of six crystalline matrices and their mixtures for the MALDI of lignin and studied the effect of sample application technique and matrix-to-analyte ratio on the quality of the mass spectrum. It was found that the best results can be obtained when α-cyano-4-hydroxycinnamic and 2,5-dihydroxybenzoic acids, and also 2,4,6-trihydroxyacetophenone are used as matrices, taken in 10- to 100-fold excesses with respect to lignin and sequentially applied onto the target in the order analyte-matrix-analyte. The use of ionic liquids as martices for obtaining lignin MALDI mass spectra was proposed for the first time. It was shown that the N-tert-butyl-N-isopropyl-N-methylammonium α-cyano-4-hydroxycinnamate ionic liquid, which forms a homogeneous solution with lignin, gives substantially better results compared to crystalline matrices in the intensity and reproducibility of the mass spectra obtained. The structure of MALDI mass spectra of spruce dioxane lignin related to the predominance of units derived from α-guaiacylpropanone in the macromolecule is analyzed.

Solvatochromic polarity parameters for binary mixtures of 1-butyl-3-methylimidazolium acetate with water, methanol, and dimethylsulfoxide

Solvatochromic polarity parameters (ETN, a, β, and π*) for binary mixtures of 1-butyl-3-methylimidazolium acetate-ionic liquid, which is a promising solvent of lignocellulosic materials with water, methanol, and dimethylsulfoxide, are determined via UV spectroscopy. A Redlich-Kister (CNIBS/R-K) equation modified for a quasi-ideal binary solvent is used to describe algebraically the dependences between the Dimroth-Reichardt energies, the Kamlet-Taft parameters, and the composition of binary mixtures. The addition of molecular solvents to the ionic liquid in significant amounts was shown to produce no radical changes in its polarity or donor and acceptor characteristics, due to the incorporation of a cosolvent into supramolecular clusters formed by alkylimidazolium cations.

Rapid determination of 1,1-dimethylhydrazine transformation products in soil by accelerated solvent extraction coupled with gas chromatography–tandem mass spectrometry

ABSTRACT A method for the analytical extraction of mobile species of eightmain transformation products of 1,1-dimethylhydrazine (formaldehyde dimethylhydrazone, acetaldehyde dimethylhydrazone, 2-furaldehyde dimethylhydrazone, 1,1,4,4-tetramethyl-2-tetrazene, N,N-dimethylformamide, N-nitrosodimethylamine, 1-methyl-1H-1,2,4-triazole, and 1-formyl-2,2-dimethylhydrazine) from soils using subcritical acetonitrile at a pressure of 100 bar is proposed. The effects of temperature, number of extraction cycles, and the moisture content of soil samples on the recovery of analytes were studied. It was found that, for soils with high concentrations of lignin humic substances, efficient extraction can be attained with an addition of significant amounts of alkali to the soil (2.5 g/g). Under the optimum conditions, the recovery of analytes was higher than 70% at the extraction time no more than 30 min. A combination of the proposed sample preparation approach with analysis by gas chromatography–tandem mass spectrometry (GC-MS/MS) ensures the determination of the products of unsymmetrical dimethylhydrazine (UDMH) transformation in complex matrixes, such as soils with high concentrations of organic substance with detection limits from 1.8 to 15 µg kg–1 using the direct injection of the extract into the chromatography system. The error of determination at a confidential probability of 0.95 was not worse than 15% even for analyte concentrations close to lower limit of quantitation (LLOQ) values. The method developed is a significant improvement compared to the highly efficient methods previously reported in literature differing from them with simple sample preparation, rapidity, low consumption of reagents, the possibility of simultaneous determination of eight compounds and 1–2 orders of higher sensitivity. It was successfully used for the analysis of real samples of peaty soil from the place of impact of the first step of a carrier rocket.

Direct determination of hydrazine, methylhydrazine, and 1,1-dimethylhydrazine by zwitterionic hydrophilic interaction liquid chromatography with amperometric detection

ABSTRACT A promising alternative to ion-chromatographic methods currently used for the direct determination of hydrazines is provided by hydrophilic interaction liquid chromatography (HILIC). In this work, we propose a method for the simultaneous determination of hydrazine, methylhydrazine and 1,1-dimethylhydrazine in natural waters and soils based on a combination of chromatographic separation on a zwitterionic sulfobetaine stationary phase (Nucleodur HILIC) in the HILIC mode with amperometric detection. Effects of different factors on the retention of analytes were studied and the optimum conditions of analysis were found. We recommend a mixture of acetonitrile with an aqueous phosphate buffer solution of pH 2.5 (78:22 v/v) with an ionic strength of 20 mM as a mobile phase. Detection in the direct current mode was performed at a working electrode potential of 1.1 V. The advantages of the method are the high efficiency of separation, rapidity, high sensitivity and a wide dynamic range of analyte concentrations, covering four orders of magnitude. The attained LOD values for analytes lie in the range 0.07–0.13 μg L–1, which is two orders of magnitude lower than those in currently used methods of ion chromatography with electrochemical and mass spectrometric detection. The method was validated on samples of natural waters of different origin using the added–found technique. It was found that the error of analysis did not exceed 10% for river and ground waters and increased to 20–30% for peat bog surface waters. The possibility of application of the developed method to the analysis of soils was shown on samples of peat bog soils selected at places of impact of the first steps of carrier rockets and polluted by rocket fuel based on 1,1-dimethylhydrazine.

Formation of low molecular weight oligomers from chitin and chitosan stimulated by plasma-assisted processes.

The controlled degradation of solid powders of chitin and chitosan stimulated by electron-beam plasma (EBP) was experimentally studied. Crab shell chitin and chitosan were used as original substances. The non-equilibrium low temperature EBP was generated by injecting an electron beam into a gaseous medium. Chitooligosaccharides with Mw=800-2000Da and polydispersion 1.5-2.5 were formed due to the EBP-treatment of chitin and chitosan. The β-1,4 glycosidic bounds in original polymers degrade under the action of active oxygen species produced in the EBP. Low molecular weight products of chitosan inhibited the growth of various yeast-like and filamentous fungi at minimum inhibitory concentration 500mcg/ml. By optimizing the treatment conditions and using special techniques of reaction volume formation the 95% yield of chitooligosaccharides was obtained after 2min whereas the conventional chemical hydrolysis usually takes several days. The EBP-stimulated hydrolysis is promising for effective polysaccharides degradation and can be competitive with traditional technologies.

Specific features of sample preparation upon chromatographic determination of 1,1-dimethylhydrazine and N-nitrosodimethylamine in peaty soils

The applicability of existing methods of extraction and chromatographic determination of mobile forms of 1,1-dimetylhydrazine and an important product of its oxidation transformation—N-nitrosodimethylamine—for analysis of peaty boggy soils typical for the European North of the Russian Federation is evaluated. It is shown that within a 3-day period after 1,1-dimetylhydrazine penetration into the soil, no more than 15% of its initial content may be extracted. It is revealed that the greatest amount of unsymmetrical dimethylhydrazine is extracted from peat upon distillation with steam in the medium of 40% solution of sodium hydroxide. Conditions of sample preparation and chromatographic determination of nitrosodimethylamine in soils with high organic matter content are optimized.