FTIR-ATR vs HPLC analysis of Aspartame in Soft Drinks

The purpose of this study was to rapidly determine the aspartame content in soft drinks using the Fourier Transform Infrared Spectroscopy with Attenuated Total Reflectance (FTIR-ATR) method along with partial least-squares regression (PLS). The additional PLS method was implemented in order to obtain subtle information from the FTIR spectra on the possible interference bands and overlapping peaks. The results from the FTIR-ATR method were compared to the High-Performance Liquid Chromatography (HPLC) method. Given that many beverages and foods contain low-calorie sweeteners, such as aspartame, Khurana and his colleagues, the authors of the study, state that an efficient and straightforward method of measuring aspartame content in food and beverage products is essential.

At present, the dominant method for determining aspartame content is HPLC-based. According to the researchers of this study, HPLC-based methods, as well as several other methods, are expensive and require a significant investment of time, especially when preparing the sample for analysis. Khurana and his fellow researchers suggest that the FTIR-ATR method is faster and less time consuming when compared to the HPLC method, and has been shown to be useful when quantifying chemical components in food samples.

The prediction errors between the results of the FTIR-ATR and HPLC methods were about 5% or less for each brand of soft drinks analyzed. Possible reasons for these errors could be noise interference, aspartame concentration sensitivity, or stronger absorbance of peaks due to certain stretching of functional groups from the aspartame molecule.

Khurana et. al. suggests that replications or similar future studies should use a higher concentration range of aspartame to possibly lower prediction errors due to the sensitivity of a lower concentration. This could imply that FTIR-ATR may have questionable accuracy when measuring lower concentrations of aspartame, leaving HPLC to be a superior method in such cases.

Source: Khurana, Harpreet K., Il K. Cho, Jae Y. Shim, Qing X. Li, and Soojin Jun. "Application of Multibounce Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy and Chemometrics for Determination of Aspartame in Soft Drinks." Journal of Agricultural and Food Chemistry 56 (2008): 778-83.