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Visible Spectrophotometric Analysis for the Mutual Determination of Doxycycline Hydrochloride and Iron in Real Samples after Cloud Point Extraction

Zuhair A. A. Khammas and Rana A. Rashid

A new method is described for the mutual analysis of drug doxycycline hydrochloride (DOX. HCl) and iron(III) ions in pharmaceuticals, biological and river water samples by combined cloud-point extraction and UV-Vis spectrophotometry. The method is based on the reaction between iron(III) ions and the drug DOX. HCl in acidic medium forms a brown colored Fe-DOX complex, which is subsequently extracted by cloud point extraction (CPE) using Triton X-114 as an extracting medium followed the determination of both; DOX drug and Fe(III) ions individually, using visible spectrophotometry at same wavelength maximum 430 nm. The parameters impact on the extraction efficiency of CPE methodology was studied by using the classical optimization and the interferences effect of some metal ions on the determination of iron was also investigated. The pre-concentration and enrichment factors of the method were found to be of 55.5 and 24.35 fold, respectively, achieving the detection limit of 0.07 μg mL-1 with linear range of 0.2-8 μg mL-1 (r = 0.9999) for DOX and 9.57 ng mL-1 with linear range of 20-200 ng mL-1 (r = 0.9984) for Fe(III). The mean recovery percentage was 95.95 ± 1.09 in urine sample and 101.55 ± 0.77 in river water, and the precision (RSD%) ranged between 0.21-1.09% and 0.84-2.60 % for DOX and Fe(III), respectively. The proposed method was used for the determination of DOC in the urine samples of 10 subjects orally administered with DOX tablets like Medomycin 100 mg, in addition to drug formulations, While iron was determined in two selected supplements and in both cases, the experimental values agreed with the quoted values as stated by the manufacturer company.