Total organic carbon, TOC

Last changed: 08 September 2022

The most common method (and which we use) is directing the sample across a hot catalyst, where the carbon is combusted into CO2, which is quantified. First, inorganic carbon is removed by acidification of the sample and expulsion of the resulting carbonic acid with CO2-free gas. The final step may also expel some volatile organic forms of carbon, but these usually constitute a negligible proportion of the TOC in surface waters. 

Known issues with the parameter and/or important method changes

No problems reported.

Current method of measurement

Valid since May 2022
Method: SS-EN ISO 20236:2021 
Water samples not conserved. Preparation treatment with HCL and CO2 expulsion. The sample is subsequently combusted and produced CO2 is measured using an NDIR detector.
Instrument: Shimadzu TOC-VCPH with TNM-1 module and automatic sample changer ASI-V. 
Instrument: Shimadzu TOC-LCPN with TNM-L module with automatic sample changer ASI-L.
Note 1: The two instrument models are used in parallel.
Note 2: Sample changer with built-in stirring apparatus is used.

Previous methods

2007-01 – 2022-04
Method: Swedish Standard SS-EN 1484 1st ed.
Water samples not conserved. Preparation treatment with HCL and CO2 expulsion. The sample is subsequently combusted and produced CO2 is measured using an NDIR detector.
Instrument (since January 2007): Shimadzu TOC-VCPH with TNM-1 module and automatic sample changer ASI-V. 
Instrument (since August 2021): Shimadzu TOC-LCPN with TNM-L module with automatic sample changer ASI-L.
Note 1: The two instrument models were used in parallel.
Note 2: Since 2010-03, sample changer with built-in stirring apparatus was used.

2004-01 – 2006-12
Method: Swedish Standard SS-EN 1484 1st ed.
Instrument: Shimadzu TOC 5050 with sample injector ASI-502. Water samples not conserved. Preparation treatment with HCl and measured using an NDIR detector.

1999-01 – 2003-12
Method: Swedish Standard SS 02 81 99.
Instrument: Shimazdu TOC 5050 with sample injector ASI-502. Water samples not conserved. Preparation treatment with HCl.

1987-01 – 1998-12
Method: Swedish Standard SS 02 81 99.
Instrument: Shimazdu TOC 500 with sample injector ASI-502.
NB: Water samples conserved with HgCl2 until 1996, with H2SO4 during the period 1997-1998.