ISO 8245 pdf download.Water quality — Guidelines for the determination of total organic carbon (TOC) and dissolved organic carbon (DOC)
1 Scope
This International Standard gives guidance for the determination of total carbon (TC), total inorganic carbon (TIC) and total organic carbon (TOC) in drinking water, ground water, surface water, sea water and waste water. It also defines terms and specifies interferences, reagents, and sample pretreatment for water samples. The method described in this International Standard applies to water samples containing organic carbon content ranging from 0,3 mg/l to 1000 mg/l. The lower limit concentration is only applicable in special cases, for example drinking water, measured by highly sensitive instruments. Higher concentrations may be determined after appropriate dilution. This International Standard does not deal with the instrument-dependent specifications. Purgeable organic substances, such as benzene, toluene, cyclohexane and chloroform, can also be determined using this method. Cyanide, cyanate and particles of elemental carbon (soot), when present in the sample, can be determined together with the organic carbon.
2 Normative reference
The following normative document contains provisions which, through reference in this text, constitute provisions of this International Standard. For dated references, subsequent amendments to, or revisions of, this publication do not apply. However, parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent edition of the normative document indicated below. For undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC maintain registers of currently valid International Standards. ISO 5667-3, Water quality — Sampling — Part 3: Guidance on the preservation and handling of samples .
3 Terms and definitions
For the purposes of this International Standard, the following terms and definitions apply. 3.1 total carbon TC sum of organically bound and inorganically bound carbon present in water, including elemental carbon 3.3 total organic carbon TOC sum of organically bound carbon present in water, bonded to dissolved or suspended matter, including cyanate, elemental carbon and thiocyanate 3.4 dissolved organic carbon DOC sum of organically bound carbon present in water originating from compounds passing through a membrane filter of 0,45 mm pore size, including cyanate and thiocyanate 3.5 volatile organic carbon VOC purgeable organic carbon POC organic carbon present in water which can be purged under the conditions of this method 3.6 non-volatile organic carbon NVOC non-purgeable organic carbon NPOC organic carbon present in water which cannot be purged under the conditions of this method
4 Principle
Organic carbon (org. C) in water is oxidized to carbon dioxide by combustion, by the addition of an appropriate oxidant, by UV radiation or any other high-energy radiation. The application of the ultraviolet method with only oxygen as an oxidant is restricted to low polluted waters, containing low concentrations of TOC . NOTE In the presence of humic material, low TOC values may be obtained when UV radiation is used. The carbon dioxide formed by oxidation is determined either directly or after reduction, for example to methane (CH 4 ). The final determination of CO 2 is carried out by a number of different procedures, for example infrared spectrometry, titration (preferably in non-aqueous solution), thermal conductivity, conductimetry, coulometry, CO 2 -sensitive sensors and flame ionization detection (used after reduction of CO 2 to methane, among others). In addition to organic carbon, the water sample may contain carbon dioxide or ions of carbonic acid. Prior to the TOC determination, it is essential that this inorganic carbon be removed by purging the acidified sample with a gas which is free from CO 2 and organic compounds. Alternatively, both total carbon (TC) and total inorganic carbon (TIC) may be determined and the organic carbon content (TOC) may be calculated by subtracting