Determination of tacrolimus in pharmaceutical formulations by validated spectrophotometric methods

Abstract

Two simple, rapid and sensitive spectrophotometric methods were developed for the determination of tacrolimus in pharmaceutical dosage forms. The methods, based on the sulphuric acid reaction and on the iodine charge-transfer reaction, gave absorption peaks at 295 nm and 365 nm, respectively. The calibration curves were linear in the concentration range of 30- 55 μg mL-1 for the sulphuric acid method (r²=0.9999) and 5-10 μg mL-1 (r²=0.9999) for the charge-transfer method. The specificity was assessed, showing that there was no interference from the excipients. The accuracy of both of the methods was higher than 99.44%, with a bias lower than 2%, and high precision was also demonstrated. The limits of quantitation for the two methods were 30 μg mL-1 and 5 μg mL-1. The proposed methods were applied to the determination of tacrolimus in capsule dosage forms, and the results compared statistically with the validated reversed-phase liquid chromatography (RP-LC) method, showing significant correlation (p<0.05) and demonstrating either method to be an excellent alternative to LC. The application of these simple methods to routine quality control analysis of pharmaceuticals could contribute to their safety and therapeutic efficacy.