Caffeine Flow Through Ftir Sensor Based

The concept of a novel FTIR flow-through sensor is presented on the example of caffeine determination in soft drinks. The system is based on the placement of a solid phase sorbentinside a standard flow through cell (optical path: 70 µm) being the particle size appropriate to be fitted without leaking. By using a SI-manifold, pre-conditioning, sample-sensorinteraction and sorbent regeneration were performed in an automated and highly reproducible way.
The sensor has been characterized in terms of activation of the solid sorbent, sample volumeinjection, efficiency of the retention process and regeneration step. Moreover, it was in-house validated for the quantitative determination of caffeine by evaluation of the followingparameters: linearity, linear range, sensitivity, limits of detection (LOD) and quantification (LOQ) and precision. The characterization and validation results clearly demonstrate thecapability of flow through FTIR sensor to determine non-polar molecules such as caffeine at parts per million level.
Comparing the features of the developed sensor with those of themost recently precedent based on ATR-FTIR spectroscopy [1] also for caffeine determination, it can be seen that the LOD and LOQ has been improved by a factor of 3-4, the analysis timehas been reduced to approximately a half and the selectivity of the methodology has been also improved by selecting a narrow and characteristic caffeine band for its determination.Furthermore, the sensor can be easily adapted to the analysis of polar, non-polar, cationic and anionic molecules by changing the solid support, providing interesting possibilities forthe development of new applications in the trace analysis of organic molecules.

[1] M. C. Alcudia-León, R. Lucena, S. Cárdenas, M. Valcárcel, Anal. Chem., 2008, 80, 1146-1151.