DETERMINATION OF ALKENYL SUCCINIC ANHYDRIDE (ASA) IN PULP AND PAPER SAMPLES

A method for the determination of alkenyl succinic anhydride (ASA) in pulp, paper and water samples is presented. The method, based on gas chromatography (GC), enables the determination of ASA in its different forms, that is fiber-bound ASA and unbound ASA. The latter normally comprises metal soaps of alkenyl succinic acid. In order to distinguish between bound and unbound ASA, the unbound ASA must first be extracted from the sample. In this study, were have shown that unbound ASA can be efficiently extracted from paper either with acidic acetone or acetone in the presence of KH2OP. Acetone alone is not the proper solvent, since unbound ASA in paper often occurs as Ca-soaps which are not very soluble in acetone. For GC analysis, derivatization of the extracted components is necessary. Regarding determination of bound ASA, acid methanolysis on one hand, and alkaline hydrolysis followed by methylation with diazomethane on the other, gave similar recoveries of bound ASA. The different derivatization methods evaluated here, namely silylation, methylation with diazomethane, and methylation during acid methanolysis, all resulted in similar amounts of detected ASA. Resin acids may severely interfere with the quantification of ASA due to overlapping in GC analysis. This is especially true for wood-containing or rosin-sized paper grades, where resin acids are abundant. For reliable quantification, GC-MS used in selected-ion-monitoring (SIM) mode is recommended.