Sources of Measurement Variability and Their Effect on the Transfer of near Infrared Spectral Libraries

The use of near infrared spectroscopy for the rapid identification of raw materials has now become widely accepted. In order to facilitate the ease of use of such libraries it is beneficial to be able to transfer libraries from one instrument to another without making any adjustments to the spectral data or the spectral library. Often variability between samples from the same lot, instruments, sampling conditions and environmental conditions impact the performance of a spectral library. These factors also influence the ability to transfer a library or calibration from one instrument to another. To see how large an effect these variables have, a study of various cellulose powders was undertaken to measure the variability resulting from: glass vials, grades of material and lots and instruments, as well as day-to-day variation. It was found that the sources of variation had contributions in the order: material > day-to-day measurements > material lots > vial type > instrument.