The aligned chromatograms were subsequently reduced to 866 points by taking one of every 5 points and the mean of the repli cates was calculated. To eliminate the effect of irreproducibility which was closely related not only with the loss of sensitivity in the fiber over time but also to the detector, the data matrix was submitted to a row profile pretreatment. This scaling method con sists of dividing each value of the original variables by the row sum Cerrato Oliveros and others 2005)