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A simple, rapid, and sensitive method is developed for the simultaneous determination of hydrazine, methylhydrazine, and 1,1-dimethylhydrazine in waters based on precolumn derivatization with benzaldehyde and the determination of the resulting products by reversed-phase HPLC with spectrophotometric detection at 300, 282, and 298 nm, respectively. The effect of imine and micellar catalysis is applied for the first time to obtain hydrazine derivatives on their simultaneous presence. The conditions of derivatization are chosen: the type, pH and concentration of the buffer system; the concentration of the reagent and the surfactant; and the temperature and duration of the reaction. It is found that the derivatization reaction proceeds completely at pH 9.4 in the presence of a catalytic system based on 0.6 M ammonium and 87 mM sodium dodecyl sulfate, and also 3.5 mM reagent at room temperature for 5 min. The quantitative yield of the derivatization products is confirmed by ion chromatography. The limits of detection (S/N = 3) without additional preconcentration are 0.3, 2.3, and 1.3 μg/L, and the linearity range is 1–500, 7–1000, and 5–1000 μg/L for hydrazine, methylhydrazine, and 1,1-dimethylhydrazine, respectively.

Novel stationary phases based on aminopropyl silica gel covalently modified with poly(ethylene glycol) (PEG) with different matrix-to-polymer mass ratios are obtained. The chromatographic properties of the adsorbents are studied using the Tanaka test procedure for hydrophilic stationary phases (and by way of example of separating model mixtures of sugars, amino acids, and water-soluble vitamins). It is shown that varying the thickness of the layer of (PEG) not only affects the efficiency but also makes it possible to tailor the selectivity toward polar analytes in the hydrophilic interaction liquid chromatography mode.

A method for identifying straits of rocket kerosene (RG-1 and T-1 brands) and various types of hydrocarbon fuels (aviation fuel TC-1 and diesel fuel) in soil has been developed. The proposed version of identification is based on the preliminary separation of the main components by gas chromatography and their mass spectrometric detection followed by the processing of the data obtained by chemometric methods of analysis (principal component analysis and projection on latent structures with discriminant analysis) using the “MZmineZ,” “iMet-Q,” and “MetaboAnalyst” software. A possibility of the application of the developed approach to the typification of saturated oil fractions of different origin is illustrated.

Using an example of tetraphenyltin (TePT), a new method is developed and tested for the isolation and preconcentration of toxic organometallic compounds from soils. It consists in the preconcentration of the target component in an organic layer formed after the splitting of a microemulsion (ME), followed by the determination of TePT by reversed-phase HPLC with spectrophotometric detection. The dependence of the TePT concentration factor in the organic layer formed after the splitting of the ME on the composition of the ME is studied. It is found that, in using a ME of the composition sodium dodecyl sulfate–n-hexane–n-butanol–water (3 : 1.5 : 6 : 89.5, by volume), the concentration factor is maximal and equal to 10. The limit of detection for TePT is 0.1 ng/mL.

The review covers the research of the Laboratory of Chromatography of the Division of Analytical Chemistry of the Department of Chemistry of Moscow State University in the development of new stationary phases for hydrophilic interaction liquid chromatography and ion chromatography performed in 2007–2017. The principles that guided the team in selecting matrices for each type of adsorbents, approaches to the modification of surface, and the methods of forming functional layers are discussed. The revealed regularities of changes in the chromatographic properties of materials on varying the structural fragments of the functional layers are described in detail, which enabled the authors to develop approaches to obtaining stationary phases that are not inferior to commercial analogs in efficiency and selectivity.

Chromatographic analysis of orange and apple juices is provided using novel covalently-bonded poly(styrene-divinylbenzene)-based (PS-DVB) hyperbranched anion exchanger for suppressed ion chromatography (IC) with improved selectivity toward inorganic anions and organic acids. The obtained stationary phase provides baseline resolution of weakly retained organic acids such as glycolate, acetate, lactate, and formate, which are not separated to baseline with modern commercially available anion exchangers. The proposed method is validated with respect to linearity, recovery, limits of detection, and intra-day and inter-day precision.

A possibility of the identification of semi-volatile hydrocarbon fuels in soil samples by studying the distribution of biomarkers of the sesquiterpane class is shown. The extraction of a soil sample with methylene chloride and the subsequent analysis of the extract by gas chromatography–mass spectrometry ensured the detection of these hydrocarbons in RG-1 and T-1 rocket kerosenes, TS-1 aviation kerosene, and diesel fuel. It was found that the distribution of the compounds found is characteristic for each type of fuel and is preserved in their transformations in the soil. The parameters reflecting the distribution of biomarkers and ensuring the identification of the type of fuel at any stage of transformation are proposed.

In this work, simple, rapid and highly sensitive method of hazardous chemical 1,1-dimethylhydrazine (unsymmetrical dimethylhydrazine, UDMH) determination based on pre-column derivatization with unsubstituted aromatic aldehydes and reversed-phase high performance liquid chromatography-ultraviolet-tandem mass spectrometry (RP HPLC-UV-MS/MS) has been developed. Along with benzaldehyde, commercially available aromatic aldehydes, namely: 2-naphthaldehyde, 2-pyridinecarboxaldehyde, and 2-quinolinecarboxaldehyde, were used as derivatizing reagents in the analysis of hydrazines for the first time. The reactions were studied in a wide pH range by varying reaction time and other conditions. A slightly alkaline pH 9 was shown to be optimal for the derivatization of UDMH by aromatic aldehydes. The quantitative yield of derivatization products under the established conditions was confirmed by HPLC analysis with amperometric detection. For all studied reagents, wide linear ranges of concentrations (0.01–1000 μg/L) in natural water samples were observed. The limits of detection for UDMH in natural water were in the 3.7–130 ng/L range. 2-Quinolinecarboxaldehyde was selected as the most appropriate reagent for HPLC-UV-MS/MS determination of UDMH. In case of using this reagent, the accuracy was in the range of 97–102%, and precision, expressed as RSD was less than 8%. The developed approach does not require laborious stages of pre-concentration and isolation of UDMH from natural water components.

The development of new high-performance anion-exchange stationary phases is one of the priority tasks of modern ion chromatography (IC). Most of the research in this field is aimed at improving the selectivity of anion exchangers and increasing the sensitivity, efficiency, and rapidity of the analysis. The selectivity of the stationary phases is largely determined by the chemistry of the adsorbent surface; therefore, it is particularly important to understand the relationship between the structure of the functional layer of the anion exchanger and its chromatographic properties. This review is devoted to methods for modifying polymer matrices in order to obtain highly efficient anion exchangers for the separation of inorganic and organic anions.

For the first time novel pellicular anion-exchangers with functional layers of quaternized branched polyethyleneimine (PEI) covalently bonded to the surface of aminated poly(styrene-divinylbenzene) (PS-DVB) with 1,4-butanediol diglycidyl ether (1,4-BDDGE) as a linker are obtained and studied. The proposed method of synthesis includes alkylation of PS-DVB substrate containing secondary aminogroups with 1,4-BDDGE followed by amination with branched PEI containing primary, secondary, and tertiary amino groups. Quaternization of amino groups of PEI required for increasing ion-exchange capacity of the stationary phase is provided with two epoxides – glycidol and 1,4-BDDGE, which results in the considerable variations of ion-exchange selectivity. Chromatographic properties of the obtained anion-exchangers are evaluated using various model mixtures of anions (F − , HCOO − , CH 3 COO − , C 2 H 5 COO − , Cl − , BrO 3 − , NO 2 − , Br − , NO 3 − , ClO 3 − , S 2 O 3 2− , C 2 O 4 2− , CrO 4 2− , SO 4 2− , PO 4 3− , I − , SCN − ) in hydroxide and carbonate/bicarbonte eluents. All anion-exchangers show better selectivity toward the anions of weakly retained organic acids (acetate, formate, propionate) as compared with previously reported chemically derivatized anion-exchangers with monomeric functional sites in the ion-exchange layer. In terms of separation abilities, novel anion-exchangers with covalently-bonded PEI are not inferior to some commercial columns with grafted polymeric anion-exchange layer. Anion-exchanger quaternized with more hydrophilic glycidol packed in 10-cm long column enables the separation of 16 anions including weakly retained and highly retained polarizable ones within 26 min using gradient elution. Column efficiencies for both anion-exchangers with quaternized PEI are up to 32000 N/m and 37000 N/m in case of hydroxide and carbonate eluent, respectively, which is comparable with the values demonstrated by commercially available columns of related chemistry.

In this paper, we assessed snow pollution by nitrogen-containing substances including rocket propellants – UDMH (unsymmetrical dimethylhydrazine, (СН3)2NNH2) and NT (nitrogen tetroxide, N2O4) – and their transformation products (NDMA (nitrosodimethylamine, (CH3)2NNO), NO3−, NO2− and NH4+) within the falling regions (FRs) of the first and second stages of Proton-M rockets launched from the Baikonur Cosmodrome. At the first stage FR in Central Kazakhstan, snow with a pH range from 1.7 to 9.0 was contaminated by N-containing substances (maximal value in g/L): UDMH – 0.27, NDMA – 0.04, NO3− – 19, NH4+ – 0.04 and NO2− – 0.13. The first stage landing resulted in snow contamination by soil dust particles and N-containing substances at a rate of 13 g/m2 and 82 mg/m2/day, respectively. The maximal permissible addition (MPA) for UDMH, NDMA and NO3− to the 0–5 cm layer of soil was estimated at 0.06, 0.006 and 70.2 mg/m2, respectively. At the second stage FR in the NE Altai, substances released by space transportation were absent and the concentration of NO3− and NH4+ corresponded to the natural background level. The index of contamination (IC) was used for characterizing the degree of snow contamination by N-containing substances. A simulation model was developed for analysing the dependence of snow contamination by rocket propellant components on the weather parameters.

The chromatographic properties of three hyperbranched anion exchangers having various diamines in the external part of the functional layer are studied in order to reveal diamine influence on selectivity toward mono- and divalent organic acids. The obtained stationary phases have the same structure of the internal part of the functional layer formed by repeating 4 modification cycles including alkylation with 1,4-butanediol diglycidyl ether (1,4-BDDGE) and amination with methylamine (MA) and differ by the structure of diamine used in the 5th modification cycle. For the first time several diamines (ethylenediamine, (2-aminoethyl)aminoethanol, and N,N'-bis(2-hydroxyethyl)ethylenediamine) are used for completing the last modification cycle in hyperbranching. The performance of three prepared anion exchangers is investigated using KOH and NaHCO3 as eluents and discussed with respect to the differences in hydrophilicity of the external part of the functional layer showing its effect on the separation of organic acids.

Evaluation of the chromatographic properties of covalently bonded hyperbranched stationary phase based on poly(styrene-divinylbenzene) (PS-DVB) and containing zwitterionic fragments in the structure of functional layer was conducted in suppressed ion chromatography (IC), reversed phase high performance liquid chromatography (RP HPLC), and hydrophilic interaction liquid chromatography (HILIC) modes. Besides the possibility of resolving 20 inorganic anions and organic acids using KOH eluent in suppressed IC, prepared resin provided the separation of alkylbenzenes in RP HPLC, water-soluble vitamins, amino acids, and sugars in HILIC mode. Trends in the retention of hydrophobic and polar analytes on the prepared stationary phase indicated the dominating effect of analyte nature on the retention mechanism and proved satisfactory hydrophilization of PS-DVB surface with hyperbranched functional layer for retaining polar compounds. The obtained results revealed good prospects of using hydrophobic PS-DVB substrate for preparing stationary phases for mixed-mode chromatography.

A new highly sensitive and rapid approach to the determination of 1,1-dimethylhydrazine in natural water is developed (determination range is 0.03–1 μg/L). It is based on the use of high-performance liquid chromatography–tandem mass spectrometry with precolumn derivatization by phenylglyoxal and does not require any preconcentration. Derivatization, chromatographic separation conditions, and tandem mass spectrometry detection parameters are chosen. Intra-day precision of the results of measurements of 1,1- dimethylhydrazine in natural water is 12–16%, and inter-day precision is 16–22%. The lowest limit of detection and the lowest limit of quantification are 0.010 μg/L and 0.030 μg/L, respectively.

A procedure for sensitive determination of rocket kerosene in water is described; it includes the dispersive liquid–liquid microextraction of analytes followed by their separation and determination by gas chromatography mass spectrometry in the mode of chromatogram registration against selected ions (m/z: 67, 81, 85, 95, 136, 137, 174, 183, and 193). The effect of the nature and volume of disperser and extraction solvents, salt additives, and the extraction duration on the efficiency of extraction of analytes is studied. The detectable concentration range is 0.005–0.05 mg/L. The detection limits (S/N = 3) of kerosene RG-1 and T-1 are 0.0015 and 0.0022 mg/L, respectively. The repeatability of the measurement results for the above range varies from 16 to 9% (n = 3); the intermediate precision varies from 20 to 12% (n = 5).

A number of covalently-bonded hyperbranched poly(styrene-divinylbenzene)-based (PS-DVB) anion exchangers having functional ion exchange layers of different branching degrees are prepared and investigated. The attachment of the hyperbranched functional layers to the substrate surface is realized via anchor secondary amino groups inserted into the polymeric backbone by means of acylation with acetic anhydride followed by reductive amination with methylamine. Further modification of the obtained secondary amino groups is provided by repeating the steps of alkylation with 1,4-butanediol diglycidyl ether (1,4-BDDGE) and amination of the terminal epoxide rings with methylamine (MA). The variation of the number of cycles including modification with 1,4-BDDGE and MA results in selectivity alterations for the obtained anion exchangers. Chromatographic parameters of the obtained stationary phases are evaluated using the model mixtures of anions (F−, HCOO−, Cl−, EtCOO−, BrO3−, NO2−, Br−, NO3−, SO42−, PO43−) with hydroxide and carbonate/bicarbonate eluents. The anion exchangers show the increase of NO2−/EtCOO− and NO2−/BrO3− selectivity and the decrease of EtCOO−/Cl− selectivity with increasing the number of modification cycles. In case of anion exchanger obtained after three modification cycles, the calculated values of column efficiencies for polarizable NO2− and Br− are up to 18,000 and 16,000 N/m, respectively.

In the last decade the developments in the field of ion chromatography (IC) were aimed at increasing the efficiency, sensitivity and rapidity of analysis, as well as on improving separation selectivity. Since selectivity and efficiency to the large extent depend on the surface chemistry of the stationary phase, the development of novel anion exchangers remains one of the priority tasks in modern IC. The exact chemistry of commercially available resins is not known and not many literature data devoted to the procedures of preparing anion exchangers for IC have become available in the last 10-15 years. However, the knowledge about the surface chemistry of anion exchangers can provide understanding of the trends in selectivity and efficiency changes, as well as help with the choice of the stationary phase type suitable for solving a particular analytical task. The current review is devoted to the methods of preparing anion exchangers based on polystyrene-divinylbenzene (PS-DVB) and ethylvinylbenzene-divinylbenzene (EVB-DVB) for IC of inorganic and small organic anions and is aimed at demonstrating the improvement of their performance over the years, which was brought by the development of the new types of stationary phase architecture.

Three covalently-bonded poly(styrene-divinylbenzene)-based (PS-DVB) hyperbranched anion exchangers prepared using primary amines with carboxylic, sulfonic or 2-hydroxyethyl substituents in the internal part of the functional layer were studied and compared for evaluating the effect of amines substituents on the chromatographic performance of the stationary phases. The hyperbranched coating was created on the surface of aminated PS-DVB substrate by repeating the modification cycles including alkylation with 1,4-butanediol diglycidyl ether (1,4-BDDGE) and amination with primary amine; glycine, taurine (2-aminoethanesulfonic acid) or ethanolamine were used in the first cycle, and 4 more cycles were conducted with methylamine (MA). The influence of the structure and type of primary amine used in the first cycle on the retention and selectivity toward inorganic anions, short-chain carboxylic acids, and polyphosphates was investigated using hydroxide eluent. The effect of temperature on the separation of organic acids was also studied for all stationary phases, which revealed the possibility to control and improve resolution for some pairs of analytes.

Novel polystyrene-divinylbenzene (PS-DVB) based anion exchangers differing from each other in the structure of the branched functional ion exchange layer are prepared to investigate the role of linker and functional site on ion exchange selectivity. The proposed method of synthesis includes the obtaining of aminated PS-DVB particles by means of their acylation with following reductive amination with methylamine. Further modification of the obtained secondary aminogroups is provided by the alkylation with either 1,4-butanediol diglycidyl ether (1,4-BDDGE) or resorcinol diglycidyl ether (RDGE), which form the linkers of different hydrophobicity, and amination of terminal epoxide rings with trimethylamine (TMA), dimethylethanolamine (DMEA), methyldiethanolamine (MDEA) or triethanolamine (TEA). The variation of the structure and hydrophobicity of the linker and terminal quaternary ammonium sites in the functional layer allows the alteration of selectivity and separation efficiency of the obtained adsorbents. The ion exchange selectivity and separation efficiency of the anion exchangers are evaluated using the model mixtures of anions (F(-), HCOO(-), Cl(-), NO2(-), Br(-), NO3(-), HPO4(2-) and SO4(2-)) in potassium hydroxide eluents. The adsorbents show the decrease of selectivity with increasing the hydrophilicity of the terminal functional site. The anion exchangers having more flexible and hydrophilic 1,4-BDDGE linker provide smaller separation factors for most of the analytes as compared with RDGE-containing adsorbents with the same terminal ion exchange sites, but are characterized with higher column efficiencies and better peak symmetry for polarizable anions. In case of 1,4-BDDGE-modified anion exchangers of the particle size of 3.3μm functionalized with DMEA and MDEA the calculated values of column efficiencies for polarizable NO3(-) and Br(-) are up to 49,000 and 53,000N/m, respectively, which is almost twice higher than the values obtained for the RDGE-containing analogues.

A method has been developed for determining rocket kerosene (RG-1 and T-1) in soil by static headspace analysis with subsequent gas chromatography–mass spectrometry analysis. It has been shown that the headspace analysis of a solid sample is the preferred approach to sample pretreatment compared with the ultrasonic extraction by methanol and the analysis of the equilibrium headspace collected above the extract. The effects of the temperature, the incubation time of the sample, and the moisture of the sample on the extraction and the sensitivity of the headspace determination of rocket kerosenes in soils of different nature have been considered. It has been found that 1 cm3 of the headspace collected above the sample at the temperature of 90°C for 20 min should be injected into a chromatograph (splitless injection mode) to determine the mass concentration of kerosenes in soil in the range of 50–500 mg kg–1. To determine the concentration in the range of 500–20000 mg kg–1, 0.1 cm3 of the headspace collected under similar conditions should be injected into a chromatograph (split mode, 1: 10). The repeatability of the measurements for the studied concentration ranges is 12–6% and the intermediate precision is 14.3–7.4%. The gas chromatography analysis takes 41 min.

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.

Novel polystyrene–divinylbenzene (PS-DVB) based anion exchangers having branched structure of ion exchange functional groups are prepared and characterised. Two proposed synthetic methods include acylation of PS-DVB microspherical particles followed by reductive amination with dimethylamine or methylamine, which results in obtaining tertiary or secondary amino groups on the surface, respectively. Further alkylation of amino groups was provided by reaction with either (3-chloro-2-hydroxypropyl)trimethylammonium chloride or glycidyltrimethylammonium chloride, which allowed the simultaneous insertion of trimethylammonium functional group and hydrophilic spacer into the structure. The other considered option is reaction with diglycidyl ethers, which requires further amination of terminal epoxide rings with trimethylamine. The proposed approaches resulted in preparation of the ion exchangers with extended linear or branched anion exchange structure with trimethylammonium groups located at a distance from the surface and connected via hydrophilic linkers. The ion exchange selectivity and separation efficiency of obtained anion exchangers are studied for the model mixture of inorganic anions (F−, HCOO−, Cl−, NO2 −, Br−, NO3 −, H $$ {\text{PO}}_{ 4}^{2 - } $$ and $$ {\text{SO}}_{4}^{ 2- } $$ ) using hydroxide eluents. The adsorbents with branched ion exchange layer having three positively charged sites in the structure of attached groups demonstrate superior column efficiencies and better peak symmetry as compared with anion exchanger having linear structure with two positively charged sites in the chain. In case of branched anion exchangers the calculated values of column efficiencies for polarisable NO3 − and Br− are 44,000 and 50,000 N/m, respectively, and significantly higher than 7,000 and 8,000 N/m obtained for anion exchanger with linear structure of the ion exchange layer.

Polyelectrolyte anion exchangers based on commercially available nonsulfonated silicagels Silasorb 600 and Kromasil with modification of the latter by quaternized poly(4-vinylpyridine) have been proposed. Sorbents based on Kromasil allow simultaneous determination of 10 anions (CH3COO−, HCOO−, BrO 3 − , Cl−, NO 2 − , NO 3 − , I−, SCN−, ClO 4 − , SO 4 2− ) for 20 min and show high efficiency (up to 30000 tp/m) for NO 3 − in a variant of single-column ion chromatography with indirect spectrophotometric detection upon elution by the solutions of potassium hydrogen phthalate.

A novel method for the synthesis of anion exchangers for ion chromatography that provides the covalent attachment and spatial movement of the ion-exchange layer away from the silica surface is proposed. The new approach includes the following steps: alkylation of aminated silica with 1,4-butanediol diglycidyl ether and then amination using polyethyleneimine. The obtained anion exchanger allows the simultaneous separation of 11 anions (C2H5COO−, CH3COO−, HCOO−, BrO3−, Cl−,NO2− Br−, NO3− I−, SCN−, ClO4−) in 18 minutes and demonstrates good efficiency (up to 62,000 TP/m for I-) in the single column ion chromatography mode with indirect UV-detection using potassium hydrogen phthalate as an eluent.

To increase the efficiency of anion exchangers based on copolymers of styrene and divinylbenzene in ion chromatography a new method for spatial separation and hydrophilization of functional groups using epichlorohydrin is suggested. Synthesis consists of acylation of a matrix by acetic anhydride, reductive amination by methylamine hydrochloride, alkylation of the aminated phase using epichlorohydrin, amination by dimethylamine at the terminal chlorine atom, and quaternization of the terminal amino group with epichlorohydrin. The obtained anion exchangers make it possible to simultaneously determine eight anions (F−, HCOO−, Cl−, NO 2 − Br−, N 3 − HPO 4 3− and SO 4 2− ) and demonstrate high efficiency (more than 62000 N/m for HPO 4 2− ) in a suppressed ion-chromatography mode.

A new high-performance liquid chromatography (HPLC) method for the sensitive simultaneous determination of hydrazine (Hy), monomethylhydrazine (MMH) and 1,1-dimethylhydrazine (UDMH) based upon the derivatization of hydrazines with naphthalene-2,3-dialdehyde and the separation of the derivatives on Zorbax Eclipse AAA column in a single chromatographic run under acidic conditions (pH 2.4) was developed. Hydrazine and monomethylhydrazine derivatives were found to be strongly fluorescent at λex = 273 nm, λem = 500 nm. It was shown that UDMH derivative can be detected as non-fluorescent hydrazone at 290 nm by UV-detection. Limits of detection were 0.05 µg · L−1 for Hy and MMH, and 1 µg · L−1 for UDMH for the injection volume of 100 µL. The method was validated for water sample analysis. It proved to be selective, accurate and precise with the supplementary advantage of the simple and rapid sample preparation.

A procedure has been developed for the determination of unsymmetrical dimethylhydrazine (UDMH) based on precolumn derivatization with glyoxal and determination of the produced derivative, mono-1,1-dimethylhydrazone of glyoxal, by reversed-phase HPLC (RP-HPLC) with UV detection at 305 nm. It has been demonstrated that the reaction of UDMH with an excess of glyoxal in solution quantitatively yields one stable product within 20 min at 25°C at pH 3.5. To increase the sensitivity of UDMH determination it has been proposed to perform solid-phase extraction preconcentration of the derivative from a 25-mL sample portion on cartridges containing Strata SDB-L polymer adsorbent. The analytical range of UDMH determination in water is 0.5–10000 μg/L or 0.01–20 μg/L using preconcentration. The relative standard deviations of UDMH determination (n = 3) do not exceed 0.12 and 0.25 without and with preconcentration, respectively. The accuracy of UDMH determination is confirmed by the analysis of spiked samples and by RP-HPLC determination with preliminary derivatization with 4-nitrobenzaldehyde as independent method.

Using chromatography and spectrophotometry, it has been shown that the reaction of 1,1-dimethylhydrazine (UDMH), methylhydrazine (MH), and 2-hydroxyethylhydrazine (HEH) with excess of glyoxal (Gl) and glyoxylic acid (GlA) in aqueous solutions yields corresponding monohydrazones as single derivatization products. The derivatization reaction occurs in a quantitative yield for 20 min at 25 or 40°C for Gl and GlA, respectively (pH 3.5). The electronic absorption spectra of the derivatives have maxima in the range of 275–305 nm. The conditions for the simultaneous determination of hydrazines in waters by reversed-phase HPLC coupled with UV detection in aqueous solutions with preliminary derivatization are proposed. The derivatives are separated on a Zorbax SB-C18 (150 × 4.6 mm) column with a mobile phase of 20 mM phosphate buffer solution (pH 3.5) and 2–5% acetonitrile. The detection limits are 0.25–0.5 or 0.4–0.7 μg/L for the derivative of Gl and GlA, respectively.

Today the determination of hydrazines is an important application in analytical chemistry. This review shows the current state-of-the-art analyses and discusses the merits of the direct chromatographic methods for the determination of hydrazines such as ion-, ion-exclusion, ion-pair and hydrophilic interaction chromatography. The methodological aspects of the separation and detection of hydrazines are considered for these methods. Examples of hydrazine determination in real samples are presented.

The conditions of the simultaneous determination of unsymmetrical dimethylhydrazine (UDMH) and products of its transformation in aqueous solutions with ion and ion-pair chromatography and mass-spectrometric detection in the electrospray ionization mode have been selected. It has been shown that up to seven components may be determined within the limits of detection at the μg/L level. The application of the developed methods to the analysis of solutions with an initial UDMH concentration of 500 mg/L that had undergone spontaneous oxidation by atmospheric oxygen has been demonstrated. The accumulation of formic acid dimethylhydrazide, 1-methyl-1,2,4-triazole and dimethylamine has been found.

The transformation of unsymmetrical dimethylhydrazine (UDMH, a propellant component) applied at a rate of 240 g/kg to different soils was studied. The kinetic regularities of a decrease in the UDMH concentration and the accumulation of its transformation products leached out from dry and wet soils were investigated 3, 10, 30, and 90 days after its application. As the UDMH enters the soil, it vaporizes, and the elevated moisture of the soils promotes an increase in the pollutant’s concentration at the initial moment; then, the concentration differences become leveled to the end of observation. It was also shown that the higher the organic matter content in the soil, the higher the UDMH concentration. However, at the end of the observations, on the 90th day, the total UDMH concentration did not exceed 0.5% of its initial content. In order to explain the UDMH behavior in the soils, one should take into account the existence of different forms of this substance and the changes in their ratios with time. The main portion of UDMH retained by the soil in the free form is transformed during the first few days. The products of the UDMH transformation, such as 1-methyl-1,2,4-triazole, formic acid dimethylhydrazide, dimethylguanidine, and dimethylamine are formed in considerable amounts, and their concentrations should be controlled in places of UDMH spills on soils.

A method is proposed for the quantification of hydrazine by reversed-phase chromatography after its derivatization with naphthalene-2,3-dialdehyde. The conditions of derivatization and the chromatography separation on a Zorbax Eclipse XDB-C8 column in the gradient mode are optimized. The derivatization and chromatography analysis take 1 and 16 min, respectively. If fluorimetry detection (λex = 273 nm, λem = 500 nm) is used and the injection volume is 100 μL, the detection limit is 0.05 μg/L. The procedure is applicable to the quantification of hydrazine in natural waters and soil extracts. A simple and rapid procedure is elaborated for the determination of 0.1–50 μg/L hydrazine in natural waters, RSD = 12% (n = 3).

The review considers the main approaches used for the determination of hydrazine and its derivatives by spectrophotometric and fluorometric methods. Examples of their determination in real samples are presented. The advantages and disadvantages of the proposed analysis scenarios are discussed and the trends of the method development are considered.

It is shown that, for a correct determination of the total concentration of unsymmetrical dimethylhydrazine (UDMH) in soil, it is necessary to consider the simultaneous presence of active products of its transformation, capable of hydrolysis to the parent compound, such as formic acid 1,1-dimethylhydrazide (FADMH). A comparative study is performed of the methods known in the literature for sample preparation to select conditions for the quantitative extraction of UDMH bonded by various mechanisms to organic and mineral fractions of soil, as well as FADMH as one of the most common active transformation products. It is found that the distillation with a 40% NaOH solution with an addition of Na2S enables the quantitative recovery of UDMH and FADMH from soils of all types and the determination of the maximum concentration of UDMH in the analysis of real samples of contaminated soils, which allows us to recommend this option to determine the total concentration of UDMH.

New anion exchangers for ion chromatography with functional groups of trimethylammonium and 3-chloro-2-hydroxypropyl-N,N-dimethylammonium were obtained. The synthesis included consecutive acetylation of a styrene-divinylbenzene copolymer containing 25% divinylbenzene, reductive amination of carbonyl groups, and subsequent alkylation. Iodomethane and epichlorohydrin were used as alkylating agents. The chromatographic properties of anion exchangers were studied by means of suppressed ion chromatography with conductometric detection. Anion exchangers with the 3-chloro-2-hydroxypropyl-N,N-dimethylammonium group are characterized by better selectivity and higher efficiency for polarizable nitrate and bromide ions, as well as for nonpolarizable chloride, fluoride, nitrite, phosphate, and sulfate ions, compared to those of sorbents with the trimethylammonium group.

New anion exchangers with the trimethylammonium functional group were prepared as a result of three-step synthesis involving the acylation of styrene-divinylbenzene copolymer with 25% cross-linking, the reductive amination of carbonyl groups, and subsequent methylation. Two methods of reductive amination were studied, and optimal conditions for this process were chosen. Chromatographic properties of the adsorbents were examined in a mode of ion chromatography with suppressed background conductivity and conductometric detection. The obtained anion exchangers demonstrated good selectivity, and the maximum efficiency was 30000 TP/m.

Procedures are developed on the basis of liquid chromatography/mass spectrometry for determining the transformation products of unsymmetrical dimethylhydrazine in soils: formic acid dimethylhydrazide (1-formyl-2,2-dimethylhydrazine, analytical range 0.01–20 mg/kg), 1-methyl-1,2,4-triazole (analytical range 0.05–100 mg/kg), 1,1-dimethylguanidine (analytical range 0.05–100 mg/kg), and dimethylamine (analytical range 0.25–250 mg/kg). The measurements were performed in the mode of chemical ionization under atmospheric pressure followed by the registration of positive ions corresponding to the protonated forms of the components to be determined. A version of ion chromatography was elaborated for separation. For sample pretreatment, the use of extraction with methanol (for 1-formyl-2,2-dimethylhydrazine) and ultrasonic extraction with a weakly alkaline buffer solution (for other substances) was proposed.

An approach is proposed for the simultaneous determination of formic acid N,N-dimethylhydrazide and 1-methyl-1-H-1,2,4-triazole (ecotoxicants formed upon the oxidative transformation of unsymmetrical dimethylhydrazine) in soils in the concentration range 0.05–50 mg/kg using gas chromatography/mass spectrometry. The conditions for the quantitative extraction of the components by continuous periodic extraction with methanol have been found. The adsorption of formic acid N,N-dimethylhydrazide and 1-methyl-1-H-1,2,4-triazole from solutions by soils of different types has been studied and a method has been proposed for preparing uniform model soil samples with the required contaminant concentrations.

The influence of the nature of the ion-pair reagent (IPR) using sodium octylsulfate, octylsulfonate, and dodecylsulfate as an example on the separation of asymmetric dimethylhydrazine (ADMH) and its decomposition products has been investigated using a Synergi Hydro RP column. It has been shown that the use of sodium octylsulfate as an IRP is preferable. The approach to simultaneous determination of hydrazine, methylhydrazine, ADMH, N-nitrosodimethylamine, and tetramethyl-2-tetrazene with detection limits in water matrices of 0.3, 0.7, 0.8, 7, and 1.2 μg/L respectively (sample volume of 100 μL) has been proposed.

The influence of eluent composition (the nature and concentration of the ion-pair reagent, medium pH, the concentration of the buffer solution, and the content of acetonitrile) on the retention of asymmetric dimethylhydrazine and its decomposition products on hydrophobized silica gels under the ion pair chromatography conditions was studied. It was shown that, for these sorbates, the influence of ion-pair reagents can be described correctly in terms of stoichiometric models. Empirical dependences of the retention of the components studied on the concentration of the buffer solution and the volume concentration of acetonitrile were determined. Conditions for the separation of the components were suggested.

Several monolithic macroporous polymer sorbents (pore size 1–2 µm) based on alkyl methacrylates and ethylene glycol dimethacrylate as a cross-linking agent were prepared by free radical copolymerization in columns 3×150 mm. The influence of compositions of the reaction mixture and porogens and the nature of the alkyl radical in a mixture of monomers on the hydrodynamic and chromatographic characteristics of the monoliths was studied. The monoliths based on n-butyl methacrylate have rigid macroporous morphology and excellent hydrodynamic characteristics (flow rate up to 5 mL min−1). The efficiency of separation of a mixture of benzene and its derivatives in the version of reversed-phase HPLC was shown to increase with an increase in the fraction of a lauryl methacrylate additive (LMA) in the reaction mixture. The maximum separation efficiency (number of theoretical plates (tp)) was 35 000 tp m−1 for the monolith based on n-butyl methacrylate with 7% LMA in the reaction mixture.

High-performance liquid chromatography and mass spectrometry were used to find that the decomposition of asymmetric dimethylhydrazine (I) in soils occurred with the formation of dimethylamine, formaldehyde dimethylhydrazone, methylhydrazine, trimethylhydrazine, N-nitrosodimethylamine, 1-methyl-1,2,4-triazole, formic acid dimethylhydrazide, 1,5,5-trimethylformazane, 1-methyl-1,6-dihydro-1,2,4,5-tetrazine, N,N-dimethylaminoguanidine, and several other products. High-reliability structure identification was achieved using independent methods, including gas chromatography-mass spectrometry, 1H and 13C NMR, and UV spectroscopy, and by measuring retention times and spectral characteristics after the counter-synthesis of the suggested structures. The products of the decomposition of I potentially capable of forming initial I and characterized by high migration mobility in soils were identified.

Anion-exchange resins have been prepared by chloromethylating 50%-crosslinked styrene-divinylbenzene copolymers (PS/DVB) followed by amination with trimethylamine. In addition to ion exchange, interactions with the anion-exchange matrix considerably contribute to the retention of polarizable anions on these sorbents. Additives in the eluent that can suppress adsorption sites of the stationary phase can decrease this effect. p-Hydroxybenzonitrile (0.15 mmol/L) in the eluent increases the NO3− peak efficiency from 820 to 5100 theoretical plates per meter.

Anion-exchange resins have been prepared by a two-step process that comprises the acylation of polystyrene/divinylbenzene (PS/DVB) with 50% crosslinking and subsequent amination with trimethylamine. The spacer arm between the quaternary ammonium functionality and the polymer backbone in these resins contains three, four, or five carbon atoms. An increase in the spacer arm improves the separation efficiency, affects the selectivity, and produces more symmetric peaks.

A new decomposition product of 1,1-dimethylhydrazine (UDMH), 1-formyl-2,2-dimethylhydrazine (FDMH), was found in water and soil samples. The formation of FDMH was confirmed by LC-MS and NMR studies. The possibility of FDMH conversion to initial UDMH by alkaline hydrolysis was shown.

Based on studies of the ion-chromatographic retention of 16 aliphatic amines and hydrazines on Diasorb-130-Sulfo and Nucleosil 5 SA, the relevant ion-exchange constants were calculated. The selectivities of the retention of these compounds were compared. The mass-spectrometry detection was used after the chromatography separation. The characteristics of the mass spectra of the aliphatic amines and hydrazines were discussed. Optimum conditions of detection were determined.

Conditions were found for the group adsorption preconcentration of phosphomolybdic and silicomolybdic heteropoly acids (HPAs) in the dynamic mode on a microcolumn packed with an Amberlite XAD-8 polyacrylate adsorbent. A sorption-chromatographic method for determining phosphate and silicate ions in waters as molybdic HPAs is developed. It is based on the adsorption of HPAs followed by desorption with acetonitrile and determination by reversed-phase HPLC. The detection limits for phosphorus and silicon calculated by the 3s test were 0.5 and 0.1 μg/L, respectively.

A new procedure for the determination of 1,1-dimethylhydrazine (UDMH) in soil samples was developed. This involves the distillation of UDMH from an alkaline suspension of soil and ion chromatographic analysis of the distillate. The separation was performed on a silica cation-exchanger column with ammonium acetate buffer solution as mobile phase and amperometric detection at +1.2 V. Hydrazine (Hy) and methylhydrazine (MH), which are decomposition products of UDMH, can be determined simultaneously. The limits of detection in aqueous solutions were 0.2, 0.5 and 1 µg L−1 for Hy, MH and UDMH, respectively. The developed technique was used for investigating the behaviour of UDMH in spills of rocket fuels on soils. It was found that the addition of 4 kg m−2 UDMH resulted in a 0.02% residue one year after the soil treatment. The vertical migration of UDMH in soil was less than 50 cm.