A sensitive spectrophotometric determination of acetaminophen

A sensitive, accurate and precise spectrophotometric method is described for the determination of Acetaminophen (paracetamol, ACTP) in pure form and in pharmaceutical formulations. The principle of the method is the reduction, of Fe(III) to Fe(II) by the ACTP in the presence of o-Phenanthroline (o-Phen), when the orange-red coloured chelate complex [Fe(II)-(o-Phen)3]2+ the ferroin complex was formed, and its absorbance was measured at lambda = 510 nm. The apparent molar absorptivity, referred to ACTP was 3.16 x 10(4) 1 mol-1 cm-1 and the Sandell's sensitivity was calculated as 4.8 ng cm-2. The calibration graph was rectilinear over the range 0.25-10.0 ppm of ACTP and the regression equation was calculated as A = 2.06 x 10(-1) C + 4.78 x 10(-3) with a correlation coefficient of 0.9999 (n = 8). A statistical analysis by means of the Student's t-test as well as by the variance ratio F-test, indicates that the proposed new method is equivalent to the corresponding B. P. 1988 and U. S. P. XXII official methods with regard to accuracy and precision.