A derivative UV spectrophotometry method for the determination of levothyroxine sodium in tablets

Abstract

A derivative UV (DUV) spectrophotometric method was developed for the determination of Levothyroxine Sodium (LT4) in tablets of different doses. Quantification was performed using the second derivative of the absorption spectrum at 253 nm (2D253) in methanol : water (50 : 50; v/v) (pH 11.2). The method was validated and compared with an HPLC procedure carried out using a RP18 column (125 x~ 4 mm, 5 microm) and methanol: phosphoric acid (0.1%) (70 : 30, v/v) (pH 3) as mobile phase. Flow rate was set at 1.5 mL/min, and detection was performed at 225 nm. The proposed DUV method was linear in the range 3.0 - 40.0 microg/mL with an appropriate precision and accuracy, and it was selective for the drug under study. On the other hand, results obtained by 2D253 analysis were similar to those obtained by HPLC, with no statistically significant differences between them. Therefore, it was concluded that the developed method is suitable for the determination of LT4 in tablets at the tested doses.