A very simple resolution of the mixture paracetamol and salicylamide by flow injection–solid phase spectrophotometry Original Research Article

A continuous and simple multi-parameter sensor for the sequential determination of salicylamide and paracetamol by solid-phase UV spectrophotometry is described. The sample containing these compounds is injected and then they are concentrated on-line on to an anionic exchanger (Sephadex QAE A-25) packed in a flow-through cell and its absorbance measured continuously at 300 nm. The calibration graphs at 300 nm are linear over the range 2.5–40 μg ml−1 for paracetamol and 5–80 μg ml−1 for salicylamide in the presence of each other; the relative standard deviations were 0.60 and 0.36%, respectively, and the sampling frequency of 36 h−1. Mixtures of salicylamide and paracetamol in ratios between 1 : 5 and 5 : 1 were satisfactorily resolved. The proposed simultaneous method was applied to the determination of these compounds in pharmaceutical preparations. The procedure does not require any separation step and the sensor can be regenerated by the carrier itself. This is the first UV multi-parameter sensor showing these features.