DETECTION AND ELIMINATION OF THE CONSTANT ERROR COMPONENT AND THE INTERACTIVE MATRIX INTERFERENCE IN THE DETERMINATION OF ADSORBABLE ORGANIC HALOGEN (AOX) IN BLEACHED KRAFT PAPER PULP-MILL EFFLUENTS

A study of four types of blank, two of which (the placebo blank, PB, a nd the method blank, MB) are amenable to direct measurements and the o ther two (the total youden blank, TYB, and system blank, SE) to extrap olation, revealed the need to use a correct blank test (TYB, which eli minates the constant error component) and make analytical measurements in the presence of the matrix at two different levels of the test por tion in order to avoid its interactive interferences. The proposed met hodology enables validation of the analytical procedure used in those cases where no placebo or SRM is available for this purpose. The concl usions drawn here are demonstrated in the microcoulometric determinati on of adsorbable organic halogen (AOX) in two different bleached kraft mill effluents: one from the stage D-1 (100% CIO2) of the bleaching s equence OD1PD2 of the elemental chlorine-free (ECF) type, and the othe r for the chlorination step, the first in the conventional sequence (D 20C80)(E(0))D1D2, applied to kraft pulp from Populus spp.