Determination of lignin distribution in pulps by FTIR ATR spectroscopy

In most pulp lignin content measurements, only the average lignin content is measured and no information on the variance of the lignin content between fibres is obtained. This paper describes a new method, based on mid-infrared attenuated total reflectance spectroscopy and multivariate data analysis, to determine the variation of lignin content in pulp fibres. It was shown that laboratory-cooked and mill-cooked hardwood kraft pulps have a much higher uniformity than mill-cooked softwood pulp and the softwood kraft pulp became more uniform after oxygen delignification. The pulp lignin content variability was not found to correlate with pulp bleachability.