Determination of the rates of formation and hydrolysis of the Schiff bases formed by pyridoxal 5′-phosphate and hydrazinic compounds

The macroscopic rate constants of formation (k₁) and hydrolysis (k₂) for the reactions of pyridoxal 5′-phosphate (PLP) with hydrazine (PLP-HY system), carbidopa (-hydrazino--methyl-β-(3,4-dihydroxyphenyl)propionic acid, PLP-CD system), hydralazine (1-hydrazinophthalazine, PLP-HL system) and isoniazid (4-pyridinecarboxylic acid hydrazide, PLP-ISO system) were fitted to a kinetic scheme that considers the different ionic species present in the medium, their protonation constants, and their individual rates of formation (k₁ⁱ) and hydrolysis (k₂ⁱ). The results obtained for the molecules bearing the hydrazine group are compared with those for the reactions of PLP with n-hexylamine (PLP-NHA system) and poly- -lysine (PLP-LYS system). Some structural effects on the individual rate constants are also examined.     

A study of redox properties of hydralazine hydrochloride,an antihypertensive drug

Hydralazine hydrochloride itself is a reducing agent and its redox properties like other reducing agents vary as the oxidizing agent and applied conditions vary. The redox properties of hydralazine were studied by spectrophotometric method. Formal redox potential of hydralazine was calculated and effect of pH was observed on redox properties of hydralazine.     

Atomic Emission Spectrometric Determination of Antazoline,Hydralazine, Amiloride,Thiamine and Quinine Based on Formation of Ion Associates with Ammonium Reineckate.

Abstract

Ion-associate complexes of Antazoline HC1 (I), Hydralazine HC1 (II), Amiloride HC1 (III), Thiamine HC1 (IV) and Quinine sulphate (V) with ammonium reineckate were precipitated and their solubilities were studied as a function of pH, ionic strength and temperature. Saturated solutions of each ion-associate under the optimum precipitation conditions were prepared and the metal ion-content in the supernatent was determined. The solubility products were thus elucidated at different temperatures. A new accurate and precise method using direct coupled plasma-atomic emission spectrometry for the determination of the investigated drugs in pure solutions and in pharmaceutical preparations is described. The drugs can be determined by the present method in the ranges 0.3-3.0, 0.19-1.96, 0.3-3.0, 0.33-3.37 and 0.78-7.82 mg/25 ml solutions of I, II, III, IV and V, respectively.     

Versatile ligational behavior of azopyrazolone derived from hydralazine

Five complexes of 3-methyl-4?-(phenylhydrazono)-1-phthalazinyl-2-pyrazolin-5-one (LH) were synthesized. The ligand and complexes were characterized using elemental analyses and various analytical techniques such as IR, UV, NMR, mass spectra, magnetic susceptibility measurements, and thermal decomposition studies such as TG/DTG. The geometries of the complexes with special emphasis on the versatile ligational behavior of LH are discussed. All five complexes have octahedral geometry. In four of the complexes [M(LH)Cl₃] where M?=?Fe(III)/Cr(III) and [M(LH)(OAc)₂H₂O] and M?=?Cu(II)/Ni(II), the ligand was neutral and tridentate. Another copper complex [CuL(OAc)(H₂O)₂] in which the ligand is tridentate, mono-anionic one was also obtained in an excess of aqueous solution. Antifungal studies of the compounds are also carried out.     

X‐Ray Photoelectron Spectroscopy and Electron Microscopy of Hydralazinium Ion‐Selective Electrode Membrane's Surface

New hydralazinium (Hz) plastic membrane electrodes of either conventional or coated‐wire type were constructed based on incorporation of Hz‐phosphotungstate (Hz‐PT) ion associate or Hz‐reineckate (Hz‐Rn) ion‐pair in poly(vinyl chloride) membranes. The (Hz‐PT)‐based electrodes required 30 minutes conditioning time to exhibit nearly Nernstian response over the concentration range 1.58×10^?5–1.7×10^?2 M HzCl. They also showed life span of 17 days, working pH range of 3.2 to 9.4 and high selectivity for Hz towards Na⁺, K⁺, Mg²⁺ and Ca²⁺. The electrodes have not lost their efficiency at temperatures elevated up to 60 °C. They were successfully employed to assaying HzCl in a pharmaceutical preparation. The electrode containing (Hz‐Rn) ion‐pair required 30 minutes conditioning time to show response for Hz over the concentration range 2.5×10^?5–5.6×10^?2 M. The life span of the electrode was only 8 h. X‐ray photoelectron spectroscopy was applied to investigate the effect of prolonged soaking on the membrane's surface of both types of electrodes. The surfaces of fresh and expired membranes containing Hz‐PT were also examined by electron microscopy. The results indicated that the limitation of the life span of plastic membrane electrodes is attributed to leaching of the ion exchanger from the membrane to the test solution in addition to deformation at the surface of the expired electrode.     

Time-resolved chemiluminescent analysis of hydralazine in pharmaceuticals

A new analytical method is proposed for determination of hydralazine (HZ) in pharmaceuticals—measurement of the chemiluminescence (CL) emitted after reaction with phosphoric-acidified KMnO₄. The novelty of this method is the recording of the whole CL–time profile. Such a recording is possible by use of a CL-detector operating in tandem which enables the reactants to be mixed in the measurement cell only and, therefore, the CL is reaction monitored from beginning. At the precise time the pump is stopped signal recording is triggered and so CL evolution is recorded completely. The optimum chemical conditions for the determination were 0.8 mol L⁻¹ formaldehyde, 0.3 mmol L⁻¹ KMnO₄, 4.0 mol L⁻¹ H₃PO₄, and a total flow of 0.37 mL s⁻¹. Two calibration graphs were plotted, CL intensity and area under the profile curve against HZ concentration. Exhaustive statistical analysis provided very interesting results, for example, accordance with Clayton’s theory, detection limit below 0.2 μg mL⁻¹, and linear calibration ranges from 0.2 to 5.0 μg mL⁻¹. This method was successfully applied to the determination of HZ in pharmaceuticals. Because they are usually formulated in association with diuretics and β-blockers, the method was used for analysis of HZ in pharmaceuticals that contained either HZ only or HZ with other hypotensive substances. Obtained and nominal content were approximately the same and experimental Student t values indicated there were no significant differences between the values.