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, and the method blank, MB) are amenable to direct measurements and the other two (the total youden blank, TYB, and system blank, SB) to extrapolation, revealed the need to use a correct blank test (TYB, which eliminates the constant error component) and make analytical measurements in the presence of the matrix at two different levels of the test portion in order to avoid its interactive interferences. The proposed methodology enables validation of the analytical procedure used in those cases where no placebo or SRM is available for this purpose. The conclusions drawn here are demonstrated in the microcoulometric determination of adsorbable organic halogen (AOX) in two different bleached kraft mill effluents: one from the stage D1 (100% ClO2) of the bleaching sequence OD1PD2 of the elemental chlorine-free (ECF) type, and the other for the chlorination step, the first in the conventional sequence (D20C80)(E0)D1D2, applied to kraft pulp from Populus spp.