ABSTRACT
A spectrophotometric method is proposed for the determination of oxytetracycline in pharmaceutical preparations. The method is based on the measurement of the absorbance of the molybdate-oxytetracycline complex at 404 nm (pH 5.50; mu = 0.1 M; 20 degrees C). The composition of the complex (1:1) was determined by the application of the spectrophotometric methods of Job and Bent-French (pH 5.50; lambda = 390 nm; mu = 0.1 M). The relative stability constant (K' = 10(4.6) of the complex was obtained by the methods of Sommer and Nash (pH 5.50; lambda = 390 nm; mu = 0.1 M; 20 degrees C). The molar absorptivity of the complex was 9.5 x 10(3) l mol-1 cm-1. Beer's law was obeyed over the concentration range 2.48-34.78 micrograms ml-1. The relative standard deviation RSD (n = 10) was 0.27-0.39%. The method proposed can be applied to the assay of oxytetracycline in capsules. The detection limit of oxytetracycline is 2.5 micrograms ml-1.
Subject(s)
Oxytetracycline/analysis , Capsules , Hydrogen-Ion Concentration , Indicators and Reagents , Molybdenum/chemistry , Oxytetracycline/chemistry , Solutions , Spectrophotometry, UltravioletABSTRACT
It has been established that the antibiotic pefloxacin (Abaktal) methanesulphonate reacts with Fe(III) at pH 1.00-8.00 to form a water-soluble complex with maximum absorbance at 360 nm. The composition of the complex, determined spectrophotometrically by the application of Job's, molar-ratio and Bent-French's methods, was pefloxacin: Fe(III) = 1:1 (pH = 2.50; lambda = 360 nm; mu = 0.1 M). The relative stability constant, obtained by the methods of Sommer and Asmus was 10(5.02) (pH = 2.50; lambda = 360 nm; mu = 0.1 M). The molar absorptivity of the complex at 360 nm was found to be 4.8 x 10(3) l mol-1 cm-1. Beer's law was followed for pefloxacin concentrations of 2.15-85.88 micrograms ml-1. The lower sensitivity limit of the method was 2.15 micrograms ml-1. The relative standard deviation (n = 10) was 0.57-1.07%. The method can be applied to the rapid and simple determination of pefloxacin in aqueous solutions and tablets.
