On-line multicomponent determination of the flux of mixtures of phenols through a liquid membrane in real time

The analysis of mixtures of four phenolic compounds in an on-line system us ing UV-visible measurements with a fibre optic probe is discussed in this w ork. The aim of this system is to provide accurate real time concentration profiles in order to monitor the transport of phenols across a solid suppor ted liquid membrane in both the feed and stripping phases. Different calibr ation models are taking into account the pH of the solution, using experime ntal designs and the first derivative in combination with different multiva riate approaches like multiple linear regression (MLR), inverted least squa res (ILS) and partial least squares regression (PLS). The comparison of all these combinations is carried out by means of the predictive residual erro r sum of squares (PRESS) evaluated from an independent set of spectra. From this comparison it is concluded that a PLS model using first derivative sp ectra offers the most accurate and robust prediction in the permeation expe riments. Additionally, the stability of the model and the figures of merit obtained are also discussed.