DETECTION, INTERPRETATION AND CORRECTION OF CHANGES IN THE INSTRUMENTAL RESPONSE OF NEAR-INFRARED MONOCHROMATOR INSTRUMENTS OVER TIME

A new approach is proposed for the detection of changes in the instrum ental response of near-infrared spectrometers over time. This approach is based on simulating possible instrumental differences and performi ng a principal component analysis of the simulated data set. This mult ivariate approach is tested on a real near-infrared data set and the r esults are compared to those obtained by the several univariate diagno stic procedures commonly used to check the stability of the response o f a near-infrared spectrometer over time. Advantages and drawbacks of this new approach are discussed. A simulated data set is used to study the influence of using different types of standards on the results ob tained by this approach.