Multivariate Analysis of Hemicelluloses in Bleached Kraft Pulp Using Infrared Spectroscopy

Abstract

The hemicellulose composition of a pulp significantly affects its chemical and physical properties and thus represents an important process control variable. However, complicated steps of sample preparation make standard methods for the carbohydrate analysis of pulp samples, such as high performance liquid chromatography (HPLC), expensive and time-consuming. In contrast, pulp analysis by attenuated total internal reflection Fourier transform infrared spectroscopy (ATR FT-IR) requires little sample preparation. Here we show that ATR FT-IR with discrete wavelet transform (DWT) and standard normal variate (SNV) spectral preprocessing offers a convenient means for the qualitative and quantitative analysis of hemicelluloses in bleached kraft pulp and alkaline treated kraft pulp. The pulp samples investigated include bleached softwood kraft pulps, bleached hardwood kraft pulps, and their mixtures, as obtained from Canadian industry mills or blended in a lab, and bleached kraft pulp samples treated with 0-6% NaOH solutions. In the principal component analysis (PCA) of these spectra, we find the potential both to differentiate all pulps on the basis of hemicellulose compositions and to distinguish bleached hardwood pulps by species. Partial least squares (PLS) multivariate analysis gives a 0.442 wt% root mean square errors of prediction (RMSEP) for the prediction of xylan content and 0.233 wt% RMSEP for the prediction of mannan content. These data all support the idea that ATR FT-IR has a great potential to rapidly and accurately predict the content of xylan and mannan for bleached kraft pulps (softwood, hardwood, and their mixtures) in industry. However, the prediction of xylan and mannan concentrations presented a difficulty for pulp samples with modified cellulose crystalline structure.

Nanostructural deformation of high-stiffness spruce wood under tension

“…S10), or deuterated ( Fig. S11) and through comparison with literature data 24,25,[38][39][40] from similar fractionation experiments and FTIR measurements on the isolated polymers (For details see SI). Crystalline and surface cellulose were readily distinguished by deuteration but there were more limited opportunities for unambiguous measurement of glucomannans and xylans.…”

Characterization of Polypropylene Composite Reinforced with Wood Flour or Cellulose Fiber

“…A decrease in the strain ratio will cause a decrease in crystallinity. According to FTIR, pulp bleaching results had a higher crystallinity value than those of all treatments [13,15,16]. The higher the crystallinity value means the better the physical and mechanical properties of the composite.…”