Organic carbons and TOC in waters: An overview of the international norm for its measurements

Many chemical measurements are subjected to international recommendations and rules. When applied to environment, they must also respect national rules. In this paper, rules to measure TOC issued in the period 1973-2002 are presented. Over 20 rules and guidelines, both national and international, are presented all aiming to increase the environmental monitoring capacity of ecologists and researchers through the use of the best instruments commercially available and manufactured by the market farms. The tracking of CO2, obtained by oxidative system, is the heart of TOC modern analysers. Practically, all the methods foresee the determination of the CO2 produced by the degradation of the organic matter present in solution, often IR devices are used. Also, other detectors can be used (conductivimeter, CO 2electrode) but they must be characterised by mechanical resistance and stability, not interfered by other gases, not easily corroded. The thermal oxidation methods are distinguished in low-temperature method (below 100°C) and high-temperature method (between 600 and 1200°C) with the presence also of mixed oxidation systems. In many countries, TOC determination is ruled in order to avoid that manufacturers of scientific equipment manage at their commercial convenience on this field. Anyway, the rules imposed by internationally recognised organisms must be actually followed. They establish the use of reference solutions, specific methods of measure and detection limits that must be respected by the analytical instruments. Due to the wide field of application involving TOC measurements, especially related to water (drinking, surface, waste), this kind of instruments is largely present everywhere. At present, definitive rules about TOC measurement are not laid down by law; so, we consider it interesting to present the chronological list of the rules with their content concerning the measurement method, the sensitivity and detection limit, and the matrices that must be subjected to the control. Consideration about the measurement quality and the correspondence between rules and analytical power are out of the interest of this work. © 2004 Elsevier B.V. All rights reserved.