ABSTRACT
In the photochemical degradation of ciprofloxacin, 1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-7-(piperazinyl)-3-quinolone carboxylic acid, two major decomposition products are formed in acidic solution. The main degradation product, after both artificial and daylight exposure, was 7-amino-1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-3-quinolone carboxylic acid. This product was also the dominating compound after more than 5 h irradiation with a high-pressure mercury lamp in aqueous solutions at pH < or = 2 when the solvent additionally contained water-miscible organic solvent. The structure of the isolated compound was elucidated on the basis of the chemical behaviour in thin-layer and high-performance liquid chromatography, and of information from infrared, ultraviolet, mass and nuclear magnetic resonance spectra.
Subject(s)
Anti-Infective Agents/chemistry , Ciprofloxacin/chemistry , Anti-Infective Agents/radiation effects , Chromatography, High Pressure Liquid , Ciprofloxacin/radiation effects , Hydrogen-Ion Concentration , Light , Magnetic Resonance Spectroscopy , Mass Spectrometry , Photochemistry , Ultraviolet RaysABSTRACT
A high-performance liquid chromatographic (HPLC) method based on diode-array detection is developed and optimized for stability studies on salbutamol. In establishing the method, the effects of mobile phase constituents (buffers, buffer concentration, pH, modifiers, organic solvents, ion-pair reagents) upon the resolution of salbutamol and its degradation products are studied. The optimum method involves the use of a LiChrosorb RP-18 column with a one-step gradient elution with acetonitrile-sodium dihydrogen phosphate (40 mM)-triethylamine (5.74 mM) (pH 3.0). The acetonitrile content is increased from 4 to 9% after 6 min.
Subject(s)
Albuterol/isolation & purification , Chromatography, High Pressure Liquid/methods , Albuterol/metabolism , Hydrogen-Ion Concentration , SolventsABSTRACT
A simple isocratic high-performance liquid chromatographic method for monitoring the photodecomposition of chlorothiazide in ethanolic solution is described. A 125-mm RP-18 column and an aqueous mobile phase containing 10% methanol and 2% acetic acid were used. The flow-rate was 1.0 ml/min and the UV detector wavelength 265 nm. Samples of 0.2 ml were taken from the reaction vessel and diluted 10-fold. The external standard method was used in the quantitative determinations. The decomposition appeared to proceed according to first-order kinetics. When the solutions were saturated with oxygen, the decomposition was greatly inhibited.
