A simple, specific, accurate and precise colorimetric method has been developed and validated for the determination of Tacrolimus (TCR) in bulk and its capsule dosage form. The proposed method involves the chemical derivatization of the drug with 2, 4-dinitrophenylhydrazine (2, 4-DNP) in the presence of an acid catalyst, followed by treatment with methanolic solution of potassium hydroxide; an intensely colored compound was formed that was measured in methanol as the diluting solvent at 439 nm. All variables affecting the development of the measured colored compound were studied and optimized. Beer's law was obeyed in the concentration ranges of 50-175 µg/ml with acceptable correlation coefficient of 0.9910. The limit of detection (LOD) and limit of quantification (LOQ) for this method were found to be 5.0051 and 15.1671 µg/ml respectively. The % relative standard deviations for intra-day and inter-day precision studies were found to be less than 2%. The % recovery of TCR was found to be 98.51-100.49% confirming accuracy of the method. The proposed method was applied successfully for the determination of TCR in bulk and in its capsule dosage form without interference of any matrix additives proving its specificity.
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