Spectrophotometric determination of hydrazine and 1,1-dimethylhydrazine,separately or in admixture

A rapid, sensitive spectrophotometric method for the determination of hydrazine and 1,1-dimethylhydrazine, separately or in mixtures of varying proportions, is described. The analysis is based on the well-known reaction of these compounds with salicylaldehyde to form, in the case of hydrazine, a symmetrical azine, or with 1,l-dimethylhydrazine, a hydrazone. Absorbance measurements were made in the ultraviolet at wavelengths characteristic of the derivatives and of salicylaldehyde; the results were calculated by means of simultaneous equations. The procedure is sensitive to concentrations of hydrazine as low as 0.3 μg/ml and of 1,1-dimethylhydrazine as low as 0.25 μg/ml. This corresponds to initial sample solutions having a concentration of 3.0 mg of hydrazine and 1.25 mg of 1,1-dimethyl hydrazine per ml.     

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

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.     

Fluorometric determination of hydrazine and ammonia separately or in mixtures

Hydrazine and ammonia are often added to boiler water to inhibit corrosion. The reagents o-phthalaldehyde and mercaptoethanol have been found to form derivatives with hydrazine and ammonia which can be determined by fluorimetry. Because the optimum pH values for formation of the hydrazine and ammonia derivatives were different, analysis of mixtures of the two components without prior separation was possible. Simulated wet-lay-up boiler water samples containing 5-200-mug/ml levels of hydrazine and ammonia have been analysed with an average relative error of about 10%.     

Determination of hydrazine and 1,1-dimethylhydrazine as salicyldehyde derivates by liquid chromatography with electrochemical detection

Summary Determination of hydrazine and 1,1-dimethylhydrazine after derivatization with salicylaldehyde was done using high-performance liquid chromatography with electrochemical detection. The oxidation of the phenolic group of salicylaldazine (S-HY) and salicylaldehyde-1,1-dimethylhydrazone (S-UDMH) was optimized with respect to ionic strength, pH, and applied potential. Less than 5 ng of S-HY and S-UDMH could be detected. The detection limits for hydrazine and 1,1-dimethylhydrazine solutions were estimated to be 0.025 and 0.20 ppm, respectively.     

Electrochemical determination of hydrazine and methyl- and 1,1-dimethylhydrazine in air

An electrochemical cell capable of detecting levels of hydrazine, methylhydrazine (MMH) and 1,1-dimethylhydrazine (UDMH) in air is described. It is coupled with a dynamic air-sampling system and electronic control and amplification circuitry to provide a direct-reading portable analyser. The characteristics of this monitoring instrument are discussed. While most of the reported data are specifically for MMH vapour analysis, qualitatively similar results can be obtained when using this instrument for hydrazine or UDMH measurements.     

Separation of 1,2-dimethylhydrazine metabolites by high-pressure liquid chromatography.

The separation of 1,2-dimethylhydrazine, azomethane, azoxymethane, methylazoxymethanol, methylazoxymethanol acetate, formaldehyde and methanol by high-pressure liquid chromatography on columns of C18/Corasil, muBondapak C18 and Aminex A-27 is described. The separations are highly reproducible and rapid and may be used for kinetic studies. An example of an application of these methods to the analysis of metabolites in rat urine derived from (14C)-1,2-dimethylhydrazine is reported.     

Detection and determination of formaldehyde dimethylhydrazone in mixtures with 1,1-dimethylhydrazine

Small amounts of formaldehyde dimethylhydrazone (FMDH) present as impurity in unsymmetrical dimethylhydrazine (UDMH) give a yellow color (λ_max = 456 nm) on heating with excess of sulphuric acid; the detection limit is 50 μg ml^? FDMH. Differences in the basicity of the two compounds in anhydrous acetic acid and in methanol are used to determine the two compounds in mixtures containing ? 5% (w/w) FDMH.     

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

5-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 hydrazine, monomethylhydrazine, 1,1-dimethylhydrazine, and 1,2-dimethylhydrazine by nonaqueous capillary electrophoresis with amperometric detection

The present study is concerned with the application of nonaqueous capillary electrophoresis (NACE) with electrochemical detection (ED) to the separation and quantitative determination of hydrazine (Hy) and its methyl derivatives. The best performance of NACE-ED was found when using 4 mM sodium acetate/10 mM acetic acid/methanol: acetonitrile = 1:2 as the running buffer, with a bare platinum working electrode set at +1.0 V in an end-column amperometric detection cell. The choice and ratio of suitable solvents for the separation and injection media played an essential role for the performance characteristics of the method. The limits of detection for Hy, methylhydrazine, symmetrical dimethylhydrazine, and unsymmetrical dimethylhydrazine were 5, 2, 12, and 1 ng/mL, respectively. This is between one and two orders of magnitude lower than that achieved by previously reported CE-ED methods in aqueous buffer systems in conjunction with various types of chemically modified electrodes. The practical utility of the new NACE-ED methodology is demonstrated in terms of the determination of traces of Hys in spiked environmental samples containing a wide range of explosives and related compounds.     

Gas-chromatographic determination of 1,1-dimethylhydrazine in water

A gas-chromatographic procedure for the determination of 1,1-dimethylhydrazine in water was developed on the basis of its reaction with 4-nitrobenzaldehyde yielding the corresponding hydrazone, the extraction of the latter from water with an organic solvent, its subsequent preconcentration by evaporation, and the determination on a gas chromatograph with a nitrogen-phosphorus detector. The determination limit of 1,1-dimethylhydrazine is 0.03 μg/L. The relative error of the determination is no larger than 22% in the concentration range 0.06–0.60 μg/L and 33% at a level of 0.03 μg/L.     

Quantitative determination of cortisol in human plasma by high-pressure liquid chromatography.

A method is described for the determination of cortisol in human plasma by high-pressure liquid chromatography. The simplified extraction procedure makes the method applicable to routine clinical assays. Partition chromatography is carried out on a Zorbax-Sil column with the eluent system dichloromethane-ethanol-water. A 78% recovery was obtained for cortisol. The detection limit is 1 mug per 100 ml in 1 ml of plasma. Cortisol values were determined in samples from a random selection of patients.     

The determination of nitrofurantoin and some structurally related drugs in biological fluids by high-pressure liquid chromatography

A method for the determination of therapeutic concentrations of nitro-furantoin in plasma and urine is described; after extraction of the drug and the internal standard (2,6-dinitrophenol), the extract is concentrated and injected onto a reversed-phase Chromatographic system. A blank chromatogram shows no interfering peaks when detection is carried out at 365 nm. The limit of detection (ca. 10 ng ml^-1 for a 1-ml plasma sample) is about two orders of magnitude better than with existing methods. Some structurally related drugs can be extracted, chromatographed, and determined in the same way.     

Cleavage of hydrazine and 1,1-dimethylhydrazine by dinuclear tantalum hydrides: formation of imides, nitrides, and N,N-dimethylamine

The complexes (RPh[NPN]Ta)2(mu-H)4 (RPh[NPN] = RP(CH2SiMe2NPh)2) activate molecular nitrogen to give (RPh[NPN]Ta)2(mu-eta1-eta2-N2)(mu-H)2; however, addition of hydrazine to (CyPh[NPN]Ta)2(mu-H)4 promotes cleavage of the N-N bond and N-H activation to give the bridging bisimide complex (CyPh[NPN]Ta)2(mu-H)2(mu-NH)2. Substitution of the phosphine substituent from cyclohexyl to phenyl allows for characterization of (PhPh[NPN]Ta)2(mu-H)2(mu-NH)2 crystallographically. Addition of the substituted hydrazine Me2NNH2 results in formation of a mono(nitride) complex, (RPh[NPN]Ta)2(mu-H)3(mu-N). The N-N bond has again been cleaved, but the second nitrogen atom has been functionalized and ejected as Me2NH.     

Quantitation of amino acids and amines in the same matrix by high-performance liquid chromatography,either simultaneously or separately

A literature overview is presented of chromatographic methods currently in use to determine amino acids and mines (i) simultaneously, (ii) in the presence of each other by separate methods, or (iii) amines alone subsequent to their isolation from amino acids. Separation, derivatization and chromatographic conditions are summarized. Advantages and drawbacks of all three possibilities are discussed and criticized in detail.     

Simultaneous determination of potassium clavulanate and cefixime in synthetic mixtures by high-performance liquid chromatography

A simple, precise, and sensitive high-performance liquid chromatographic method was developed and validated for the simultaneous determination of potassium clavulanate and cefixime in synthetic mixture form. The analytes were separated on a C18 column by using 0.03 M disodium hydrogen phosphate buffer (pH 6.5)-methanol (84 + 16, v/v) as the mobile phase with detection at 220 nm. The method exhibited high sensitivity and good linearity in the concentration ranges of 12.5-62.5 and 20-100 microg/mL for potassium clavulanate and cefixime, respectively. The total run time for the 2 components was <8 min, and the average recovery was >101.5% with a relative standard deviation of <1.0%. The proposed method was validated according to guidelines of the International Conference on Harmonization by evaluation of linearity, recovery, selectivity, robustness, limits of detection and quantitation, and within- and between-day precision. The results obtained for the synthetic mixture show that the method is highly precise and accurate for the simultaneous determination of potassium clavulanate and cefixime.