COMBINED HIGH-PERFORMANCE AQUEOUS SIZE-EXCLUSION CHROMATOGRAPHIC AND PYROLYSIS-GAS CHROMATOGRAPHIC MASS-SPECTROMETRIC STUDY OF LIGNOSULFONATES IN PULP-MILL EFFLUENTS

An aqueous high-performance size-exclusion chromatographic (HPASEC) method for lignosulphonates was developed and optimized using a TSK G3000SW column. Curie-point pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) was used to characterize the lignosulphonates on the molecular level. Combined HPASEC and Py-GC-MS results showed that a sodium lignosulphonate standard, prepared under mild conditions, was a relatively polydisperse polymer that still contained features of a natural lignin polymer. Lignosulphonates discharged by pulp mills are more monodisperse macromoles of a relatively low molecular mass and are structurally modified to a greater extent than the sodium lignosulphonate standard. A relationship was established between the molecular mass distributions of the various lignosulphonate macromolecules and the fraction of preserved phenylpropane structural units.