Voltammetric Measurement of Lignin in Pulp and Paper Samples

A new approach for measuring lignin content of kraft pulps is described based on the voltammetric measurement of catalytic reactions involving lignin and redox mediators. This electrochemical method consists of measuring the rate of regeneration of a lignin redox catalyst in the presence of pulp following its oxidation at a voltammetric electrode. The intensity of the catalytic current generated at the electrode surface was found to be proportional to the amount of lignin present in a pulp. Within pulp types (softwood, hardwood, or oxygen delignified) linear relationships were obtained between the intensities of the generated current and a range of kappa numbers. The redox characteristics and concentration of the mediator, and the voltage sweep rate of the voltammetric procedure, are among parameters that can be tuned to obtain linear relationships with kappa number of various Pulps.