N. V. Ul’yanovskii

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.

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.

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.

Determination of triterpenoids from birch bark by liquid chromatography-tandem mass spectrometry

Pentacyclic triterpenoids from birch bark are of great interest as biologically active substances and raw materials for producing a wide range of drugs. In this work, a method for the highly sensitive determination of betulin, betulinic acid, lupeol, and erythrodiol in plant extracts based on a combination of high-performance liquid chromatography with tandem mass spectrometric detection is proposed. Mass spectra under the conditions of atmospheric pressure chemical ionization and collision-induced dissociation spectra of analytes are obtained. The conditions for mass spectrometric detection in the multiple reaction monitoring mode are optimized. The calculated detection limits are in the range 0.7–1.8 μg/L.

Determination of natural aromatic acids using supercritical fluid chromatography

Derivatives of benzoic and cinnamic acids are secondary metabolites of plants, widely distributed in nature and possessing biological activity. Supercritical fluid chromatography (SFC) is shown to provide a high performance separation of nine most important representatives of this class of compounds with selectivity, dramatically different from the reversed-phase high-performance liquid chromatography. The retention and chromatographic separation parameters of analytes for four stationary phases of different nature are compared and the effect of supercritical fluid parameters and the composition of the mobile phase onto the chromatographic separation are analyzed. The optimal separation is found to be achieved when using a silica-based sorbent with 2-ethylpyridinium linked groups. The proposed approach for determination of the above-mentioned compounds is based on the combination of chromatographic separation with multiwavelength spectrophotometric detection and provides the detection limits in the range of 13.0–51.3 μg/L and the analysis duration about 2.5 min. The approach is successfully tested on real objects, such as different kinds of wine.

Studies of reaction products of hydrolytic lignin with nitric acid

The properties of the reaction products of hydrolytic lignin with nitric acid in water—dioxane medium were studied. The products are a mixture of nitrogen-containing oligomeric compounds with high degree of polydispersity.

Supercritical fluid extraction of 1,1-dimethylhydrazine from peaty soils

Supercritical fluid extraction of a highly toxic rocket-fuel component (1,1-dimethylhydrazine, UDMH) from peaty soils with carbon dioxide is proposed as a rapid method of sample preparation for ion-chromatographic analysis. Optimum conditions of extraction have been determined. The efficiency of the UDMH extraction can be improved by basic treatments of the soil sample and by the use of proper additives to SC CO2 (cosolvents).

Study of Products of the Alkaline Decomposition of Hydrolysis Lignin by Atmospheric Pressure Photoionization High-Resolution Mass Spectrometry

A method of high resolution-mass spectrometry with acetone doped atmospheric pressure photoionization was used to study products of the alkaline solvolysis of hydrolysis lignin. It was found that the mass spectrum of the depolymerization products of hydrolysis lignin consists of about seven thousand peaks of oligomers, containing up to 10 aromatic units with an average molecular weight of 150 Da. Calculations of the elemental compositions of all detectable oligomers and their visualization on the van Krevelen coordinates allowed us to show that the studied sample differs from native (virgin released) lignin by the presence of fractions with high oxygen contents and highly unsaturated condensed structures, including polynuclear aromatic hydrocarbons. The structural units of lignin oligomers were characterized using an approach based on the collision induced dissociation of precursor ions in a broad m/z range.