A novel methodology for imaging wood pulp fibre surface lignin by fluorescence confocal laser scanning microscopy was developed. Various imaging modes and imaging conditions were explored for quantitative analysis. Acridine Orange was used for labelling lignin and the orthochromatic labelling condition was developed. With the thusly established methodology, the distribution of lignin across the fibre wall was clearly imaged. It was found that surface lignin concentration is about 2-4 times higher than bulk lignin concentration and that high concentration of lignin was also found on the fibre lumen surfaces and pit borders.
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