Determination of dihydralazine based on chemiluminescence resonance energy transfer of hollow carbon nanodots.

The famous weak chemiluminescence (CL) system of potassium permanganate and sodium bisulfite (KMnO4-HSO3-) was enhanced by the hollow fluorescent carbon nanodots (HCNs). The investigation of mechanism revealed that the enhanced CL was induced by the excited-state HCNs (HCNs⁎), which could be produced from the electron-transfer annihilation of positively charged HCNs (HCNs+) and negatively charged HCNs (HCNs-) as well as by CL resonance energy transfer (CRET) from excited SO2 (SO2⁎)/1O2 to HCNs. The dihydralazine sulfate (DHZS) had a diminishing effect on the CL of HCNs-KMnO4-HSO3- system due to the competitive consumption of O2-. Under the optimal conditions, the reduced CL signal with the concentration of DHZS was linear in the range of 1.0×10-7-7.0×10-5mol/L with a detection limit of 3.0×10-8mol/L. The relative standard deviation for seven repeated determination of 5.0×10-6mol/L DHZS was 2.1%. The established method was applied to the determination of DHZS in pharmaceutical preparations, human urine and plasma samples with good precision and accuracy.

Chemiluminescence investigation of carbon dioxide-enhanced oxidation of dihydralazine sulfate by peroxynitrite and its application to pharmaceutical analysis.

A weak chemiluminescence (CL) emission was observed upon mixing peroxynitrite (ONOO(-)) with dihydralazine sulfate (DHZS). Further experiments showed that carbonate media could enhance the CL emission significantly. Based on these observations, a novel flow injection CL method for the determination of DHZS is developed. The CL signal is linearly with DHZS concentration in the range of 0.01-3.0 microg mL(-1) with a detection limit of 3.6 ng mL(-1). The method was applied to the analysis of DHZS in pharmaceutical preparations and compared well with the high-performance liquid chromatography (HPLC) method. The CL mechanism is discussed and it is postulated that it involves nitrosoperoxocarboxylate (ONOOCO(2)(-)), which is an unstable adduct and can rapidly decompose into *NO(2) and *CO(3)(-) radical. The latter can then oxidize DHZS to give out strong CL emission.

[Determination of five components in compound hypotensive tablet by HPLC].

AIM: To establish a method for the determination of the five components (reserpine, chlordiazepoxide, hydrochlorothiazide, dihydralazine sulfate, triamterene) in compound hypotensive tablet. METHODS: The chromatography was performed using a CN column with acetontrile-0.1 mol L(-1) sodium heptasulfonate solution (7:3) and (5:5) as the mobile phases. The detection wavelength was 267 nm for reserpine, chlordiazepoxide and hydrochlorothiazide, 310 nm for dihydralazine sulfate, 360 nm for triamterene. RESULTS: The linear range of each component was tested, and the recovery and stability of each component was satisfactory, three lots of samples were determined using the method. CONCLUSION: This is an accurate and credible quality control method for compound hypotensive tablet.

Flow injection chemiluminescence determination of dihydralazine sulphate based on permanganate oxidation sensitized by rhodamine B.

A novel flow injection chemiluminescence (CL) method for the determination of dihydralazine sulphate (DHZS) is described. The method is based on the CL produced during the oxidation of DHZS by acidic permanganate solution in the presence of rhodamine B. Rhodamine B is suggested as a fluorescing compound for the energy-transferred excitation. The CL emission allows quantitation of DHZS concentration in the range 5-800 ng/mL, with a detection limit of 1.9 ng/mL (3sigma). The experimental conditions for the CL reaction are optimized and the possible reaction mechanism is discussed. The method has been applied to the determination of DHZS in pharmaceutical preparations and compares well with the high performance liquid chromatography (HPLC) method.

Application of arylosulfonic acids in analysis of antihypertensive drugs.

Suitability of four arylosulfonic acids and their sodium salts to form derivatives with hypotensive drugs were studied. New crystalline arylosulfonates of todralazine, hydralazine and dihydralazine were obtained. Physico-chemical properties of the obtained arylosulfonates were tested. Reagents mentioned above were also used in analysis of these drugs.

Spectrophotometric determination of dihydralazine in pharmaceuticals after derivatization with 2-hydroxy-1-naphthaldehyde.

A sensitive and selective colorimetric assay has been developed for the determination of dihydralazine. The method is based on the interaction of dihydralazine with an ethanolic solution of 2-hydroxy-1-naphthaldehyde to yield a water-insoluble yellow product, 1,4-bis[(2-hydroxy-1-naphthyl)methylene hydrazine]phthazine. This colour can be quantified spectrophotometrically at 420 nm. The calibration curve was linear between 0.4 and 8 micrograms ml-1 of dihydralazine. The molar absorptivity at 420 nm is 24000 l mol-1 cm-1. The method was successfully applied to the determination of dihydralazine in mixtures containing other drugs (reserpine, hydrochlorothiazide, oxprenolol, xanthinol, rutoside, chlorthalidone and bietaserpine).

Application of arylosulfonic acids in analysis of antidepressive drugs.

Suitability of three phenylsulphonyloxybenzenesulfonic acids and their sodium salts to form new derivatives with antidepressive drugs were studied. Then physicochemical properties of the obtained arylosulfonates were tested. Reagents mentioned above were also used in analysis of these drugs.

[Spectrophotometric analysis of the multicomponent system: dihydralazine sulfate, hydrochlorothiazide and reserpine]. / Untersuchungen zur spektrometrischen Analyse des Mehrkomponentensystems Dihydralazinsulfat, Hydrochlorothiazid und Reserpin.

With respect to their performance a computer aided spectrometric analysis of multicomponent system dihydralazine sulfate hydrochlorothiazide and reserpine was made under various conditions. To find out the advantageous measuring points the difference spectra were determined. The influence of the number of measuring points, the single and mixture calibration and the dimensiation of calibration matrix to accuracy and precision was investigated and the limits of the determination for the three component system are discussed.

[The quantitative determination of dihydralazine and selected metabolites in man]. / Zur quantitativen Bestimmung von Dihydralazin und ausgewählter Metabolite beim Menschen.

Dihydralazine and its metabolites were estimated in the steady-state in 9 hypertonic patients by gas chromatography. Serum levels of both dihydralazine and metabolites were very low and particularly below the detection limit. In urine and faeces about half of the dose was found mainly as metabolites, 2/3 of this in faeces. Acid labile hydrazones of dihydralazine (about 6% of the dose), primary acetylated and primary oxidized metabolites (both about 20%) were identified as main metabolites. Secondary metabolites (hydrazones, acetylated and oxidized products) were measured, too.

Application of conventional (DC) and differential pulse polarography (DPP) to the quality control of benzothiadiazines in tablets. Simultaneous determination of hydrochlorothiazide and dihydralazine sulphate in mixtures with minimization of interaction by the use of a zero covariance in the calibration.

A previous study of the polarographic behaviour of 14 benzothiadiazines having diuretic properties enabled possible reaction mechanisms to be proposed and gave the opportunity to determine the best conditions for analytical application. The results obtained with benzthiazide as an example of the unsaturated compounds, bendrofluazide as the dihydro compound, and hydrochlorothiazide determined together with dihydralazine are reported. The electroactivity of these last two substances was made the object of a mathematical study for the correction of reciprocal interference.

Dihydralazine sulfate analysis using 2-methyl-o-nitropyridine-6-carboxaldehyde.

A sensitive, selective colorimetric assay was developed for the quantitative analysis of dihydralazine sulfate. The method is based on the interaction of buffered (pH 4) dihydralazine sulfate with a methanolic solution of 2-methyl-3-nitropyridine-6-carboxaldehyde upon heating to give an orange color. This color can be quantified spectrophotometrically at 450 nm,with a lower limit of detection of 1 mug/ml. The color is stable for at least 24 hr. There is no interference from other drugs likely to be present along with dihydralazine sulfate and common excipients. The method was used successfully for the determination of dihydralazine sulfate in combination with other drugs in different commercial tablets. The developed method was applicable as a stability-indicating assay.