THREE-WAY METHODS FOR THE CALIBRATION OF CHROMATOGRAPHIC SYSTEMS:COMPARING PARAFAC AND THREE-WAY PLS

For the calibration of chromatographic systems,different methods can be used.One class of methodsutilizes three-way approaches.The calibration problem is stated in such a way that the decompositionof a three-way array can serve for the prediction of retention on new stationary phases.Two three-way approaches are presented:the Unfold-PCA and PARAFAC models.The theory ofboth methods is presented and the differences are highlighted,the main difference being that PARAFACis a trilinear decomposition whereas Unfold-PCA is not.Both three-way methods are evaluated on asmall data set consisting of retention measurements of eight solutes at six mobile phase compositions onsix stationary phases.The differences in performance of the two models are minor,For calibration purposes,two variants of the methods are discussed:three-way PLS and an extensionof PARAFAC.Again the theory and differences between the two methods are explained.The predictiveperformance of the two methods is compared using the same data set as earlier.The differences inpredictive performance,however,are minor.Both methods are capable of predicting 98% of thevariation in the test sets.Yet,there are other considerations when comparing methods than predictiveperformance,e.g.the quality of the predictions.

THREE-WAY METHODS FOR THE CALIBRATION OF CHROMATOGRAPHIC SYSTEMS:COMPARING PARAFAC AND THREE-WAY PLS

For the calibration of chromatographic systems,different methods can be used.One class of methods utilizes three-way approaches.The calibration problem is stated in such a way that the decomposition of a three-way array can serve for the prediction of retention on new stationary phases. Two three-way approaches are presented:the Unfold-PCA and PARAFAC models.The theory of both methods is presented and the differences are highlighted,the main difference being that PARAFAC is a trilinear decomposition whereas Unfold-PCA is not.Both three-way methods are evaluated on a small data set consisting of retention measurements of eight solutes at six mobile phase compositions on six stationary phases.The differences in performance of the two models are minor, For calibration purposes,two variants of the methods are discussed:three-way PLS and an extension of PARAFAC.Again the theory and differences between the two methods are explained.The predictive performance of the two methods is compared using the same data set as earlier.The differences in predictive performance,however,are minor.Both methods are capable of predicting 98% of the variation in the test sets.Yet,there are other considerations when comparing methods than predictive performance,e.g.the quality of the predictions.