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At least 73 records · Page 4Linked to original sources
PubMed1989

Determination of ethacrynic acid in pharmaceutical formulations by difference ultraviolet spectrophotometry after derivatisation with N-acetylcysteine.

A selective difference spectrophotometric procedure is described for the assay of ethacrynic acid (a diuretic drug) in pharmaceutical dosage forms. The method is based on the reaction of the drug with N-acetylcysteine at pH 7.4 and ambient temperature, affording thiol adducts having different spectral properties, and involves the measurement of the absorbance of the reaction mixture relative to an equimolar solution of unreacted ethacrynic acid. The absorbance at 270 nm (A(270)) and the absorbance difference, delta A=A(270-A(244), obtained from the difference spectrum, were found to be linearly correlated with the drug concentration. The proposed spectrophotometric procedure was applied successfully to the determination of ethacrynic acid in pharmaceutical formulations using a reversed-phase high-performance liquid chromatographic procedure as a reference method.

Acetylcysteine↗
PubMed1984

The assay of tropane derivatives in formulations by second derivative ultraviolet spectrophotometry.

The development of a second order derivative spectrophotometric assay of atropine, hyoscine and benztropine in formulations is described. The assay involves the extraction into 1,2-dichloroethane of the tetraphenylborate salt of the alkaloids precipitated from pH 6 solution by an excess of sodium tetraphenylboron and measurement of the amplitude near 273 nm to its shorter wavelength satellite in the second derivative spectrum. The second derivative amplitude gives a more precise determination of the alkaloids than absorbance. A two-point bracketing standardization of the amplitude is required owing to a small but significant intercept in the calibration data. The procedures are sufficiently sensitive and precise for the batch and unit-dose assay of tablets of atropine sulphate (0.6 mg) hyoscine hydrobromide (0.3 mg) and benztropine mesylate (2 mg), and for the assay of atropine sulphate injection (0.4 mg ml-1) and tincture of belladonna.

Atropine↗
PubMed1980

Determination of serum-phosphate without deproteinization by ultraviolet spectrophotometry of the phosphomolybdic acid complex.

Phosphate may be determined in serum without deproteinization as the phosphomolybdic acid complex by UV-spectrophotometry. The rate of complex formation is dependent on the acidity and the concentration of molybdate. The photometric measurements should be performed at a longer wavelength than in maximum absorptivity of the phosphomolybdic acid complex to permit practical high concentrations of molybdate in the reagents. Citric acid will hinder the complex formation, but will not interfere with the stability of the phosphomolydbic acid. The phosphomolybdic complex is determined by adding citric acid to the samples before (blank) and after (test) the molybdate. The analytical procedure has been automated on a Greiner GSA II, Greiner Electronics, Switzerland.

Humans↗
PubMed1983

[Quantitative analysis of a tetraribonucleotide mixture by ultraviolet spectrophotometry].

Using the least squares method we have calculated the proportions of each nucleotide of a mixture of AMP, CMP, GMP and UMP, after measuring the absorbance of the mixture every ten nanometers from 230 to 290 nm at pH 12.7 and 2. The method is very simple and rapid (the calculations are made in less than one minute), does not require a highly sensitive spectrophotometer to obtain reasonably precise results and, in contrast to the other methods of the literature, it can be applied to quantities as little as 50 micrograms of nucleotides.

Adenosine Monophosphate↗
PubMed2000

Second derivative ultraviolet spectrophotometry and HPTLC for the simultaneous determination of vitamin C and dipyrone.

Two accurate, precise and sensitive thin layer chromatographic (TLC) and second derivative UV-spectrophotometric procedures are described for the simultaneous determination of ascorbic acid and dipyrone in pure form and in pharmaceutical dosage forms. The TLC method involved direct application of methanolic solutions of tested samples on silica gel TLC plates using water:methanol (95:5 v/v) as developing system. The developed plates were then directly scanned at 260 nm using a TLC scanner. The second method depends on second derivative UV-spectrophotometry with zero crossing technique of measurement. Second derivative amplitudes at 280 and 272 nm were selected for the determination of ascorbic acid and dipyrone, respectively. Both methods show good linearity, precision and reproducibility. They are simple and do not require manipulation prior to analysis. The proposed methods have been successfully applied to the determination of the drugs in various pharmaceutical dosage forms such as tablets and ampoules.

Ascorbic Acid↗