DEVELOPMENT OF A METHODOLOGY USING METHYLENE-BLUE TO QUANTIFY THE AMOUNT OF UV-SCREEN APPLIED AND TO DETERMINE THE HOMOGENEITY OF APPLICATION ON PAPER

Methylene blue was employed as a model molecule to develop a methodolo gy to quantify the incorporation of compounds into the paper matrix. Q uantification was based on absorption and fluorescence measurements of the solutions employed to transfer methylene blue into paper. This me thodology is suitable to quantify amounts which correspond to less tha n 1% of the paper weight, and it can be applied when testing the inhib ition efficiency of UV-screens against the photoyellowing of paper mad e from mechanical pulp. In addition, two application methodologies wer e compared to establish which one led to a more homogeneous distributi on of methylene blue in paper. The 'dip method' led to a more even dis tribution than the 'drop method'. (C) 1998 Elsevier Science S.A. All r ights reserved.