Determination of assay and impurities of gamma irradiated chloramphenicol in eye ointment

A sample preparation method was developed to isolate chloramphenicol and it s radiolytic products from an oily ointment base. The isolation method susp ended the eye ointment in n-hexane at 45 degreesC, and isolated the target compounds as residue by centrifugation. It was found that the main element to ensure a satisfactory isolation was keeping the sample solution at 45 de greesC during sample preparation. Linearity, precision. accuracy and suitab ility of the method were confirmed valid for both assay and impurity tests. This isolation method was ideal for assay, unique for extraction of unexpe cted and complex radiolysis products, and had a number of advantages compar ed to the pretreatment methods described in The United States Pharmacopoeia and British Pharmacopoeia, in terms of accuracy, precision, and easy handl ing. Thc effect of gamma -irradiation on chloramphenicol eye ointment was s tudied by HPLC, after applying the developed sample preparation method. The present assay and impurity test methods with HPLC were confirmed to be sui table for irradiated chloramphenicol in eye ointment. Formation of radiolyt ic products induced by gamma -irradiation was evidenced by the impurity tes t. The assay test showed that active ingredient of chloramphenicol eye oint ment decreased by 3.3% at an irradiation dose of 25 kGy and by 11.1% at 50 kGy. (C) 2001 Elsevier Science B.V. All rights reserved.