Determination of iodochlorhydroxyquin and corticosteroids in pharmaceutical formulations

Iodochlorhydroxyquin was separated from various corticosteroids using an acetonitrile-diatomaceous earth column. Iodochlorhydroxyquin was eluted with cyclohexane, and the corticosteroid was eluted with chloroform. Iodochlorhydroxyquin was determined by both a UV absorbance method and a new compleximetric method using the nickel chelate of iodochlorhydroxyquin. The corticosteroid was determined by the blue tetrazolium and isoniazid procedures. The average percent recovery for these four methods was 100.8, 99.4,100.7, and 99.9, respectively, for 10 known mixtures. The standard deviation for the absorbance for 10 determinations of the nickel complex was 0.002 absorbance unit (0.31%). Various characteristics of the nickel and other complexes were evaluated, including the sensitivity, solubility, and wavelength of maximum absorbance in 14 different solvents. The analyses of 23 typical products are reported, for which the standard deviation, expressed as a percentage of the amount declared, was 1.31% for the UV, 1.34% for the compleximetric, 1.49% for the blue tetrazolium, and 1.22% for the isoniazid procedures. Methods of determination in the presence of interferences are discussed.