Spectrophotometric determination of trimethoprim using 2,4-dinitro-1-fluorobenzene reagent

Abstract<br /> A simple spectrophotometric method for the determination of trimethoprim (TMP) in pure form and in its pharmaceutical formulation has been described. The method is based on the reaction of TMP with 2,4-dinitro-1-fluorobenzene reagent (DNFB) in acetone medium to give a highly rosy red colored product with maximum absorption at 538 nm with a molar ratio of 1:1. Beer's law is obeyed in the range 10-75 μg/ml with molar absorptivity of 1.917x103 l.mol-1.cm-1 and Sandell's sensitivity of 0.1514 µg/cm2. Precision (RSD) better than 1.7 % and accuracy (average recovery %) is 100.76 %. The suggested method has been applied to dosage forms as tablets and compared with the pharmacopoeial method, t-test is evaluated and found 1.828 at 95% confidence limit. The results show that there is no interference are present in commercial dosage forms.