Spectrophotometric determination of tolbutamide in tablets.

Two spectrophotometric methods, Glenn's method of orthogonal function and the basic dye method, are described for determing tolbutamide in tablets without interference from the tablet excipients. In Glenn's method, the absorbance of tolbutamide in 95% ethanol is measured in the vicinity of 250--270 nm at 4 nm intervals and the p2 coefficient is calculated. The coefficient is linearly related to concentration within a range of 0.1--0.4 mg/mL. Tolbutamide gives a complex of a ratio 1:1 with basic dye Brilliant Cresyl Blue (BCB) or Safranin T (ST). The complex is easily extracted with chloroform. The absorbance of the chloroform extract is measured against either a blank or reference experiment. The latter is obtained by using a specific concentration of tolbutamide: 0.4 mg/mL in tolbutamide-BCB or 0.024 mg/mL in tolbutamide-ST. The ST complex method is more sensitive compared with the other methods. When the t-test is applied, the results of the proposed methods are more accurate than those of the traditional ultraviolet spectrophotometric method.