Determination of Doxycycline as Pure and in Pharmaceutical Preparation (Capsule) Using 4-Aminoantipyrine in Presence of Potassium Periodate

A simple spectrophotometric method for the determination of doxycycline in aqueous medium using oxidative coupling reaction has been described. The method was based on the reaction of doxycycline with 4-aminoantipyrene (4-AAP) which gives soluble and stable red colored product that gives the highest absorption at the wavelength 515 nm, and the linearity of Beer's law was in the concentration range from 5 to 110 µg/ml, and the value of the determination coefficient for the standard curve was 0.9995, which statistically indicates that it has excellent linear characteristics. The molar absorptivity was calculated and found to be 1.387x10 3 l.mol -1 .cm -1 . Sandell's sensitivity value, the Limit of detection (LOD), and ‎‏ limit of quantitation (LOQ) were calculated and equal to 0.3334 μg/cm 2 , 0.114 and 0.38 µg/ml respectively the method was successfully applied for the determination of doxycycline in its pharmaceutical preparation.