Spectrophotometric Determination of Telmisartan with the Reagent Phenol Red

In the B-R buffer solution of pH 7.9,an ion-association complex was formed by the reaction of telmisartan with phenol red,having its positive maximum absorption wavelength at 558 nm and the negative maximum absorption wavelength at 426 nm.Ranges of linearity and values of apparent molar absorptivity were found in the positive absorption region and in the negative absorption region were 6.50×10-7-1.35×10-5mol·L-1,7.50×10-7-1.00×10-5mol·L-1,and 6.59×104L·mol-1·cm-1,2.12×104L·mol-1·cm-1 respectively.The detection limits (3δ) of the method found were 1.72×10-7mol·L-1 and 8.53×10-7mol·L-1 respectively.The proposed method was applied to the determination of telmisartan in the samples of medicine,human serum and human urine,giving values of RSD (n=11) in the range of 0.72%-2.56%.