Detection and characterisation of water alcohol hydrates by on-line FTIR using multivariate data analysis

In the current work, several chemometric functions based on the principal component analysis (PCA) are studied in order to determine the number of absorbing species in an infrared data matrix acquired during a mixing process. Applying a target factor analysis (TFA), the concentration profiles of the chemical substances are obtained without the need for a calibration of the spectrometer. Different considerations concerning the objective function of the optimisation process have been tried. The chemical systems tested for such techniques are alcohol-water mixtures. The study is completed with calorimetric data that confirm the hypothesis of the presence of a hydrate suggested by the information from the spectra. The mathematically extracted concentration-time profile results are finally verified with traditional methods of quantitative analysis. This particular case will also confirm the validity of the experimental design, according to the rank compatibility test (RCT) for semibatch reactors proposed by our group.