[Effect of humidity on detection of near-infrared spectra]

Spectral performance would be affected by many factors such as temperature, equipment parameters and so on. Humidity fluctuations may occur in practice because of varying weather conditions. The objective of the present research was to find out whether the change in humidity would influence the near infrared spectrum. In this trial, an airproof, humidity-controllable test-bed was established to change the humidity of the mini environment. At 40%, 50%, 60%, 70% and 80% degrees of humidity, each sample's final spectrum was obtained by removing the background's spectrum from the sample's. As whether the influences of the sample's spectrum and the background's are equal wasn't known, this trial was divided into two groups: detecting background and sample at each degree of humidity (group 1) and background's detecting just performed at 40% degree of humidity (group 2). This research was based on the hardware of NEXUS intelligent FTIR spectrometer, made by Nicolet instrument company U. S. A, using fiber optic diffuse reflectance accessory. The final spectrum was analysed using single variance analysis and Mahalanobis distance methods. The result shows that neither in group 1 nor in group 2, humidity had little influence on NIR.