Spectrophotometric Determination of Doxycycline Hydrochloride in its pure form and its pharmaceutical preparations using reagent 2,4,6 - tribromo-anline by the Azo coupling reaction

This method is aimed at create a simple, fast, sensitive and cost-effective spectrophotometric method for measuring doxycycline hydrochloride in its pure form and in pharmaceutical preparations. The method is based on diazotization and coupling of a 2,4,6-tribromoaniline reagent in an alkaline medium to give an orange-yellow Azo dye and gave the highest absorption at a wavelength of 500 nm. After conducting numerous experiments to obtain optimal conditions, the linear relationship was governed by beer's law within the range of concentrations 0.5-24 (µg/mL),the molar absorptivity was 2.3 x 10⁴ (l.mol^-1.cm^-1), the Sandel^,s sensitivity value was 0.0205 (µg /cm²), the detection limit (LOD) was 0.0418 (µg/mL), the quantitative limit (LOQ) was 0.287 (µg/mL), and the average recovery percentage was 100.02%, With an accuracy (RSD%) of less than 0.8 %, the method showed that has good accuracy and the method was well applied successfully applied to pharmaceutical preparations as tablets and capsules.