DETERMINATION OF TOC IN SLUDGE, SEDIMENT AND SUSPENDED-SOLIDS - DESCRIPTION OF THE ANALYTICAL PROCEDURE AND ACCOMPANYING QUALITY-CONTROL PROCEDURES

The total organic carbon (TOC) is calculated by subtracting the inorganic carbon (IC) from the total carbon (TC). For TC determination, the carbon in a sample is completely converted to CO2 by decomposition/combustion in an oxygen stream. To determine IC, inorganic carbon (carbonate) is liberated by adding acid and by heating in an oxygen stream. In both cases, CO2 is quantified by infrared spectrometry. To gain reliable and reproducable results for sludge, sediment and suspended solids, at least the following conditions have to be met: particle size has to be smaller that 200 mu m; weightout has to be selected in such a way, that the signal area is not below and the signal maximum is not above specific instrument dependent parameters; combustion/decomposition has to be complete (TC: greater than or equal to 1300 degrees C, no soot) and rules for analytical quality assurance must be followed. The TC quantification of calcium carbonate is used for system calibration. Daily working procedures include calibration checks by mean control charts for TC determination of calcium carbonate and IC determination of sodium carbonate as well as for control sediment TC and IC quantifications.