Rapid determination of caffeine content in soft drinks using FTIR–ATR spectroscopy

A simple and rapid Fourier Transform infrared (FTIR) spectroscopic method was developed to determine caffeine content in soft drinks without the use of organic solvents. FTIR spectrum of carbonated beverages were characterized and the region between 2800 and 3000 cm−1 was used for quantitative estimation using partial least square (PLS) and principal component regression (PCR). FTIR spectroscopy with chemometrics, using the PLS-1st derivative spectra could predict the caffeine content accurately upto an R2 value greater than 0.97 and a standard error of prediction (SEP) of less than 2.43 with 4–6 factors in the prediction model. The developed model was applied to predict caffeine content in four commercial carbonated beverages in approximately 5 min. The developed procedure was further validated by recovery studies by comparing with UV spectroscopic method.