Simultaneous Determination of Paracetamol-containing Tablets in Binary Mixtures by pH-Potentiometric Titration and Multivariate Calibration

HAMAD.M. I. HASAN1*, Ibrahim H.I. Habib2 , Amira A. A. K. Mohammad1
Page No. 34-43

Acid-base titration method is developed for the simultaneous determination of paracetamol “PAR”
in the presence of ascorbic acid “ASC” or methionine “MET”. A 50 ml solution of binary mixture
of the cited components is titrated with 0.60 M NaOH in the presence of 0.1 M KCl and using
automatic titrator, pH electrode and stirrer. The potentiometric measurements against the volume
of NaOH are first intra/interpolated along the fixed pH range of 3 to 12.5 and then the linear
relationship between the volumes of titrant and the concentrations of analytes is plotted. The
designed models are then used to predict the concentrations of components in unknown samples
either by simultaneous equations using Cramer's rule or by classical least squares CLS regression.
Direct calculation and first derivative methods are also applicable for analysis of well separated
titration steps of PAR and ASC. The concentration ranges applied successfully for the simultaneous
determination of PAR, ASC and MET in pharmaceutical tablets are in order 35-250, 80-265 and
45-150 mg/ml. The relative errors of prediction for the two-component mixtures are 1.11% for
PAR, 1.79% for ASC and 2.13% for MET.