Networking of near infrared spectroscopy instruments for rapeseed analysis: a comparison of different procedures

A comparison of several procedures to establish a network of near infrared (NIR) spectroscopy instruments for analytical applications with rapeseed [moisture, protein, oil, glucosinolates (GSL), oleic acid (C18:1)] is presented, The procedures are (a) calibration transfer with bias adjustment, (b) standardisation with different products and different number of samples, (c) calibration with spectra of different instruments and (d) the use of a repeatability file for mininising instrument differences, The most successful procedure proved to be the use of a repeatability file of spectra of the network instruments after standardisation using rapeseed samples. Following this procedure the standard deviation of analyses in a network could be reduced by 50-66% compared to a direct calibration transfer. Calibrations for constituents with high absorptivity (e,g, moisture) could be transferred directly without a bias correction, while those for constituents with a low absorptivity (e,g, GSL) had to be transferred using a repeatability file and standardised instruments.