Physiochemical differences between dissolved and precipitated Kraft ligninfragments as determined by PFG NMR, CZE and quantitative UV spectrophotometry

A combination of analytical techniques, specifically capillary zone electro phoresis, H-1 pulsed-field gradient nuclear magnetic resonance se (diffusio n measurements and quantitative UV spectrophotometric measurements, was use d to investigate physicochemical differences between dissolved and precipit ated kraft lignin (KL)fragments, obtained from the same sample. Precipitati on was induced by heating alkaline (pOH4)Indulin AT solutions, containing v arious concentrations of NaCl (0.20-1.0 mol/L), at 75 degreesC. Depending o n the salt concentration in the samples, different amounts of KL were preci pitated. The KL precipitated at the lowest NaCl concentrations was found to consist of the largest lignin fragments whereas, at high NaCl concentratio ns, the KL fragments in the supernatants were found to be of comparably low er mean molecular weights. From the outcome of the investigation, it was fo und that the combination of analytical techniques used provides the possibi lity of collecting important information about physicochemical characterist ics related to the solution behaviour of industrial lignins.