FTIR determination of Aspartame and Acesulfame-K in tabletop sweeteners

Two different strategies for sweeteners determination in tabletop samples by Fourier transform middle-infrared (FTIR) spectrometry, an off-line and a fully mechanized extraction of Aspartame and Acesulfame-K with different mixtures of chloroform and methanol, have been developed. The off-line method involves the extraction of both active principles by sonication of samples with 25:75 v/v CHCl3/CH3OH and direct measurement of the peak height values at 1751 cm(-1), corrected using a baseline defined at 1850 cm(-1) for Aspartame, and measurement of the peak height at 1170 cm(-1) in the first-order derivative spectra, corrected by using a horizontal baseline established at 1850 cm(-1), for Acesulfame-K. Limit of detection values of 0.10 and 0.9% w/w and relative standard deviations of 0.17 and 0.5% were found for Aspartame and Acesulfame-K, respectively. The time needed for the sweeteners determination is reduced from 35 min for the HPLC method to 7 min by FTIR. On the other hand, the fully mechanized on-line extraction avoids the contact of the operator with toxic solvents and differentiates between samples that contain Aspartame and Acesulfame-K and those that include only Aspartame, reducing the time needed for the analysis of the last kind of samples to 5 min.