Determination of lignin content in high-yield kraft pulps using photoacoustic rapid scan Fourier transform infrared spectroscopy

The spectra of a number of kraft pulps from Pinus radiata with varying lignin content (Kappa number) were obtained using a rapid scan photoacoustic Fourier transform infrared (PAS-FTIR) spectrometer and a method was developed for the determination of lignin content. A partial-least-squares (PLS) model was established based on spectral data collected at different mirror velocities. The robustness of the model was statistically evaluated. The outcomes indicate that the PLS model can be used to predict Kappa number of kraft pulps with a high degree of accuracy provided that the moving mirror velocity is ⩽0.5 cm/s.