Simultaneous stopped-flow determination of paracetamol, acetylsalicylic acid and caffeine in pharmaceutical formulations by Fourier transform infrared spectrometry with partial least-squares data treatment

A simple and rapid analytical procedure is proposed for the simultaneous determination of paracetamol, acetylsalicylic acid and caffeine in pharmaceuticals by partial least-squares treatment of Fourier transform infrared spectrometric data obtained in the wavenumber range 823 and 1775 cm(-1) (PLS-FTIR) using the 14 characteristic bands included in this interval for the three compounds under study (a total of 130 absorbance data points), The method involves the leaching of the compounds to be determined from the pharmaceutical formulations with a 10% v/v solution of ethanol in dichloromethane in an ultrasonic water-bath for 20 min, filtration and direct introduction inside a liquid now cell, taking 16 cumulated scans obtained in the stopped-flow mode, For calibration a reduced set df eight standard mixtures of the three compounds assayed, considered at two concentration levels, are required, In the analysis of real and synthetic samples, precise and accurate values were obtained by PLS-FTIR, providing in all instances RSDs and accuracy errors lower than 5% and results comparable to those obtained by PLS-UV.