Showing papers on "Hydrazine published in 1984"

Liquid chromatographic-fluorescence determination of ammonia from nitrogenase reactions: a 2-min assay.

Abstract: The analytical potential of the reaction of ammonia with o-phthalaldehyde mercaptoethanol reagent at pH 7 (an atypical fluorescence) has already been demonstrated. This, coupled with additional findings reported here, has led to an ammonia determination well suited to nitrogenase studies. As a result, large numbers of samples can be rapidly analyzed by high-pressure liquid chromatrography methods under mild conditions and without prior microdiffusion. Neither sodium dithionite (or other components of the usual nitrogenase assay), nor alternative substrates (cyanide, azide, methyl isonitrile), nor their products (methylamine, dimethylamine, hydrazine) interfere. High-pressure liquid chromatography showed that the fluorescent “product” of the o-phthalaldehyde mercaptoethanol reagent-ammonia reaction was, in fact, more than just a single compound. Despite this, once the proper solvent composition was found, high-pressure liquid chromatography with a small inexpensive C18 “guard” column proved quite fast and reproducible for this measurement. Fluorescence response to ammonia was linear to at least 40 nmol/ml. A previous problem, long-term stability of the fluorescence, was solved by running the reactions in the dark. Background ammonia in the buffer could be substantially reduced by an analogous o-phthalaldehyde mercaptoethanol reagent reaction, using t-butyl mercaptan, and solvent extraction.

The technetium-catalysed oxidation of hydrazine by nitric acid

Abstract: Technetium catalyses the oxidation of hydrazine by nitric acid, a reaction which is otherwise very slow except at elevated temperatures and acidities. The reaction displays an induction period followed by a rapid destruction of hydrazine. The induction period covers an initial slow reduction by hydrazine of technetium(VII) to technetium(IV) (the initiation phase) followed by a rapid technetium(IV)-catalysed reduction of technetium(VII) by hydrazine (the induction phase). The fast reaction commences when technetium(VII) has been substantially reduced to technetium(IV). The mechanism of the fast reaction is considered to be the oxidation of technetium(IV) to technetium(VI) by nitrate, followed by reduction of technetium(VI) to technetium(IV) by hydrazine; nitrite produced in the oxidation of technetium(IV) reacts with another molecule of hydrazine to produce hydrazoic acid. On completion of the reaction, technetium is present predominantly as pertechnetate. However, traces of a coloured species are produced during the reaction and this is considered to be an analogue of Eakins Pink Compound ( trans -[(NH 3 ) 4 Tc(NO)(OH 2 )] 2+ ) which is formed by the reaction between hydrazine and technetium(IV). Hydrazoic acid is unstable in the system and is degraded, in part at least, to ammonium nitrate.

Simultaneous determination of hydrazine, methylhydrazine, and 1,1-dimethylhydrazine in air by derivatization/gas chromatography

Abstract: A rapid and simple procedure has been developed for the simultaneous determination of hydrazine, methylhydrazine, and 1,1-dimethylhydrazine in air at the parts per billion (ppb) concentration level. This procedure utilizes a chilled acetone collection medium which quantitatively traps the hydrazines and converts them to stable derivatives in a single step. The acetone solution is then assayed directly for the derivatives by using a gas chromatography with a nitrogen specific detector. The results obtained from this procedure are in excellent agreement with results obtained by independent analytical techniques, and the overall precision of the methodology is better than 5% (relative standard deviation) for 90 ppb hydrazine. The minimum detectable concentration is estimated to be approximately 4 ppb.

The high performance liquid chromatographic determination of total malondialdehyde in vegetable oil with dansyl hydrazine

Abstract: A simple high-performance liquid chromatographic (h.p.l.c.) method has been developed for determining total malondialdehyde (MDA), including free MDA and MDA released from its precursor in vegetable oils. Free MDA was reacted with dansyl hydrazine in an acidic medium, and the product, 1-dansyl-pyrazole(DP), was determined by h.p.l.c. The reaction releasing MDA from its precursor requires Fe3+ in 5% hydrochloric acid medium. Recoveries of free MDA and tetramethoxypropane (used as an MDA precursor) in vegetable oils were satisfactory. During autoxidation, a remarkable difference between the DP values of methyl oleate, methyl linoleate and some vegetable oils, and that of methyl linolenate was observed. Only methyl linolenate released MDA during autoxidation. For autoxidised methyl linolenate the DP value correlated with the thiobarbituric acid(TBA) value, although the DP value was only 30% of the TBA value.

Reactions involving the hydrazinium free radical; oxidation of hydrazine by hexachloroiridate

Abstract: Etude de l'oxydation de N 2 H 4 par IrCl 6 2− pour former N 2 et IrCl 6 3− , en solution aqueuse a 25°. On observe qu'il y a une barriere cinetique importante du transfert d'electron, compatible avec les variations de geometrie accompagnant l'oxydation de N 2 H 4

Process for removing dissolved oxygen from water using hydrazine

Abstract: A process for removing dissolved oxygen from an aqueous medium, using hydrazine to react with the oxygen, where the aqueous medium is contacted with a catalyst bed of palladium or platinum metal dispersed on a solid carrier, at ambient temperatures. The catalyst bed effects reaction of the hydrazine with the dissolved oxygen to provide residual oxygen contents of below 10 ppb. Preferably, the hydrazine is intimately mixed with the aqueous medium prior to contact with the catalyst bed. The process is especially useful in removing dissolved oxygen from recirculating aqueous medium of a steam generation system, where the hydrazine-containing aqueous medium is contact with the catalyst bed after passage through the condenser pump but prior to the feedwater heaters.

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

Abstract: 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.

A definitive synthesis of 2-[(5-methyl-s-triazolo[4,3-c]quinazolin-3-yl)thio]-N-benzylacetanilide and other reactions of its precursors

Abstract: Treatment of 2-methyl-4-chloroquinazoline 2 with hydrazine gave 2-methyl-4-hydrazinoquinazoline 3 which was converted to 5-methyl-3-mercapto-s-triazolo[4,3-c]quinazoline 4, followed by S-alkylation...

Salze der 1.2-Hydrazin-bis(dithiocarbonsäure): Darstellung, Schwingungsspektren und Struktur / Preparation, Vibrational Spectra and Structure of Alkahmetal Salts of the 1,2-Hydrazine-bis(dithiocarboxylic Acid)

Abstract: The following salts of the 1,2-hydrazine-bis(dithiocarboxylic acid) have been prepared: M2[S2CNH -NHCS2], M = Na, K and M3[S2CN-NHCS2], M = Na, K. In the solvated crystals K2[S2CNH-NHCS2] · 4 CH3OH (a = 718.0(5), b = 1329.3(8), c = 937.7(9) pm, β = 109.26(6)°, space group C2/m, Z = 2) the [S2CNH-NHCS2]2- ion possesses crystallographic C2h symmetry, i.e. a trans planar structure with a N-N bond length of 139.2(3) pm. Vibrational spectra indicate a lower symmetrical anion in the unsolvated crystals. In the trianion [S2CN-NHCS2]3- the C-N stretching vibrations are observed at 1400 and 1310 cm-1.

Hydrazine derivatives of fluorans and use thereof in electrochromic recording systems

Abstract: This invention relates to spiro[isoindole-xanthene]-3- ones, spiro[phthalazine-xanthene]-4-ones, and xanthene-3- ones useful as color-forming substances, particularly in electrochromic recording systems, which are prepared by the interaction of a fluoran with a substituted or unsubstituted hydrazine.

Photocatalytic hydrogen evolution from aqueous hydrazine solution over precious-metal/anatase catalysts

Abstract: Aqueous hydrazine solution has been photocatalytically decomposed over precious-metal/anatase catalysts yielding only H2, N2 and NH3. H2/N2(molar ratio of H2 evolved to N2 evolved) is usually ca. 1 and does not depend on the reaction conditions (pH, metal, reactant concentration). However, the value is > 1 when another hole scavenger (CH3OH) is present. N2/NH3 is ca. 0.5 and does not change in the presence of CH3OH. On the basis of these results, the reaction scheme is considered to be as follows: the electrons photoexcited into the conduction band of anatase are consumed through H2 formation and the positive holes generated in the valence band are consumed through the simultaneous formation of N2 and NH3. The dependence of the reaction rate on the concentration of N2H4 and on the metal suggests that the rate-determining step is the formation of H2 over the metal.

Tissue distribution of hydrazine and its metabolites in rats

Abstract: The tissue distribution and the urinary excretion of hydrazines, hydrazine, acetylhydrazine and 1, 2-diacetylhydrazine, were determined by mass fragmentography using a gas chromatography-mass spectrometer equipped with a multiple ion detector-peak matcher. Using the compounds labeled with a stable isotope as an intemal standard, namely the isotope dilution method, made it possible to estimate trace amounts of hydrazine and its metabolites in the tissues. Significantly high levels of all hydrazines were detected in the kidney. Especially, acetylhydrazine, a metabolite of hydrazine, accumulated to a great extent in the kidney. Free hydrazine which was liberated from acetylhydrazine was detected both in the tissues and in the urine after the administration of acetylhydrazine. This demonstrates clearly that the metabolic pathway between hydrazine and acetylhydrazine is reversible.

Hydrogen-oxygen solid electrolyte fuel cell

Abstract: PURPOSE:To obtain a low-cost fuel cell in which a platinum-system catalyst is not used by using Cu2O as a catalyst for the oxidant electrode. CONSTITUTION:Cu2O is used as a catalyst for an oxidant electrode. Cu2O in powdered form is mixed with a conductive element such as flaked graphite or active carbon in a ratio by weight of 1:10-10:1 to make an oxidant electrode. The catalytic activity of Cu2O powder tends to increase with decreased crystallinity. That is to say, it depends on grain diameter, surface area, surface state and similar factors. Among Cu2O powders, one produced by subjecting Cu(CH3COO)2 to hydrazine reduction at room temperature is preferred because it has the greatest catalytic activity.

The interaction of hydrazine hydrate with humic acid preparations at pH 4

Abstract: SUMMARY Sorption isotherms were obtained by a continuous-flow method for the interaction of hydrazine hydrate with freeze-dried hydrogen-, aluminium- and calcium-exchanged humic acid preparations in aqueous suspensions at pH 4. The application of the continuous-flow method is outlined and the fit of the isotherms to three sorption equations is examined. Microcalorimetry was used to measure directly the differential enthalpies of reaction as functions of sorptive concentrations. Exchange by hydrazinium ions of the exchangeable cations on the humates, chemisorption by interaction of hydrazine with humate carbonyl groups, and non-specific sorption involving weakly- and strongly-held hydrazinium ions and hydrazine molecules are shown to be the major sorption processes in these systems. The relative importance of each of these processes for the different hydrazine/humate systems is discussed, and the influence of the exchangeable cation on humate reactivity is considered.

Regeneration of amino compounds from the 2,4,6-trinitrophenyl derivatives by treatment with hydrazine

Abstract: 2,4,6-Trinitrophenylalanine gave free alanine and 1-hydroxy-4,6-dinitrobenzotriazole by treating with aqueous solution of hydrazine at pH 7–9 and 30 °C. Applying the reaction to partially trinitrophenylated derivative of lima bean trypsin inhibitor, the fully active protein could be regenerated almost quantitatively.