A rapid methodis provided for the on-linespectroscopic determinationof lignin content and/or kappanumber in wood pulps. Unlikecurrently available commercialinstrumentation, the methodenables one to measure lignincontent independently of speciesvariations and pulp consistency.The method includes the steps of:(1) withdrawing high-consistencysamples of wood pulp from achemical pulp manufacturingprocess; (2) subjecting these samplesto a monochromatic visible-lightsource; (3) recording the resultingscattered light and its Ramanspectrum over a predeterminedrange of wave numbers so as toproduce Raman-scattered lightintensity measurements; (4)determining either the uncorrected,baseline-corrected and/or integratedRaman-scattered light intensity ofthe samples over a predeterminedrange of wavenumbers shown by different combinations of lignin content,cellulose content, and consistency; (5) correlating byeither univariate or multivariate calibration the relationships between theRaman-scattered light intensity measurements of unknownsamples and the Raman-scattered light intensity shown by known combinations oflignin content, cellulose content, and consistencyso that the lignin content and/or kappa number in wood pulps can be accuratelydetermined over a Kappa range of 5 to 110 andpreferably 5 to 20, for any levels of sample cellulose content or pulpconsistency.
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