R. S. Smirnov

Determination of hydrazine by liquid chromatography with preliminary derivatization with naphthalene-2,3-dialdehyde

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).

A sensitive chromatographic determination of hydrazines by naphthalene-2,3-dialdehyde derivatization

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.

Determination of the products of the transformation of unsymmetrical dimethylhydrazine in soils using chromatography/mass spectrometry

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.

Precolumn derivatization with glyoxal as a new approach to the highly sensitive HPLC-UV determination of unsymmetrical dimethylhydrazine

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.

Use of ion and ion-pair chromatography with mass spectrometric detection to determine unsymmetrical dimethylhydrazine and its transformation products

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.

Effect of sample preparation conditions on the determination of the total concentrations of unsymmetrical dimethylhydrazine in soils

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.

The use of glyoxal and glyoxylic acid to determine N- and N,N-alkyl-substituted hydrazines by liquid chromatography

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.

Transformation of unsymmetrical dimethylhydrazine in soils

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.

Highly sensitive determination of 1,1-dimethylhydrazine by high-performance liquid chromatography–tandem mass spectrometry with precolumn derivatization by phenylglyoxal

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.

Determination of rocket kerosene in soil by static headspace analysis coupled with gas chromatography–mass spectrometry

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.