Comparison of two NIR systems for quantifying kaolinite in Weipa bauxites

Two laboratory-based near infrared systems were compared for the purpose of quantifying kaolinite within Weipa bauxites. The two systems were based on different instrument technologies, a Bruker MPA (multi-purpose analyser) FTNIR (Fourier transform near infrared) instrument, and a Foss Model 6500 pre-dispersive grating instrument. Systems were compared in terms of accuracy, robustness, sample throughput and ease of use. The MPA-based system was superior in terms of accuracy (root mean squared error of prediction (RMSEP) = 0.88%m/m), throughput and ease of use. The Model 6500 had an advantage of offering the most robust measurement with greater time stability and lower errors in repeated and repacked measurements. However, addition of a small number of temporally displaced and repacked samples in the calibration set improved robustness of the MPA system, matching the Model 6500.