Abstract
Numerous reports have been published regarding colorimetric determination of tetracycline but the present series of experiments were carried out in order to find a simple and more practicable method for chemical determination. The sample solution is prepared by dissolving tetracycline hydrochloride in distilled water to make a solution containing 10-100γ of tetracycline hydrochloride in 1cc. of the solution. A. 1cc. portion of this solution is placed in a glass-stoppered test tube, 2cc. of Mcllvain buffer (pH 7.0) and 0.2cc. of 0.05% aqueous solution of dimethyl-p-phenylenediamine hydrochloride are added, and mixed thoroughly. This solution, after addition of 3cc. of isobutanol and 0.2cc. of 0.02% aqueous solution of sodium hypochlorite, is shaken vigorously for 3 minutes and allowed to stand for 5 minutes at room temperature (5-30°). The blue-colored isobutanol layer is transferred to a dry test tube, 0.2cc. of absolute ethanol is added, and absorbance of this solution is measured at 630mμ. This method allows determination of a microquantity by a comparatively simple procedure and is also possible to determine the quantity of tetracycline in its preparation containing sodium metaphosphate and in tetracycline metaphosphate preparation, and also separatory determination of tetracycline in a mixture of tetracycline and chlorotetracycline.
