Total nitrogen, TotN/TNb/Total-N

Note: Total nitrogen content has previously also been calculated as the sum of Kjeldahl nitrogen and the sum of oxidized nitrogen (nitrite and nitrate nitrogen.

Known issues with the parameter and/or important method changes

Read more about total nitrogen content analyses at the Department of Aquatic Sciences and Assessment in two assessment on our various methods for analysis of total nitrogen content: Wallman et al. (2009) and Wallman et al. (2011), both in Swedish.

A popular science article about the nitrogen analyses has been written by Sonesten (2011) in the report Havet 2011 (in Swedish).

Current method of measurement (combustion)

Valid since May 2022
Method: SS-EN ISO 20236:2021 
The samples are treated with HCl. The nitrogen content is measured through chemoluminescence after catalytic oxidation into nitrogen oxides.
Instruments: Shimadzu TOC-VCPH with TNM-1 module and automatic sample changer ASI-V. .
Instrument: Shimadzu TOC-LCPN with TNM-L module and automatic sample changer ASI-L.
NB 1: The two instrument models are used in parallel.
NB 2: Sample changer with built-in stirring function is used. 

Previous methods

Combustion

2007-01 –  2022-04
Method: SS-EN 12260:2004
The samples are treated with HCl. The nitrogen content is measured through chemoluminescence after catalytic oxidation into nitrogen oxides.
Instruments (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 and automatic sample changer ASI-L.
NB 1: The two instrument models were used in parallel.
NB 2: Since 2010-03, sample changer with built-in stirring apparatus was used.

Nitrogen from persulphate

2002-01 – 2006-12
Method: Swedish Standard SS-EN ISO 11905 modified for Traacs. Bran & Leubbe Method No. J-002-88 B.
Instrument: Technicon Traacs 800.
NB: Water samples conserved with H₂SO₄.

1998-07 – 2001-12
Method: SIS 02 81 31-1 modified for Traacs. Bran & Leubbe Method No. J-002-88 B.
Instrument: Technicon Traacs 800.
NB: Water samples conserved with H₂SO₄.

1997-01 – 1998-06
Method: Swedish Standard SIS 02 81 31 modified for Traacs. Bran & Leubbe Industrial Method 55010279A.
Instrument: Technicon Traacs 800.
NB: Water samples conserved with H₂SO₄.

1988-01 – 1996-12
Method: Swedish Standard SIS 02 81 31 (modified). Bran & Leubbe Industrial Method 55010279A.
Instruments: Technicon Traacs 800 with sample changer for 120 samples. Autoclave for influx of sample.
NB: Water samples conserved with HgCl₂.