Orthophosphate, PO4-P

Samples with a concentration below the reporting limit of the Gallery instrument (4 µg/l), except samples ordered by the Department of Soil and Environment, are also analysed with the QuAAtro instrument which has a reporting limit of 1 µg/l.

Known issues with the parameter and/or important method changes

Since June 2014 are phosphate-P reported with a background correction, where influence from particles and background colour is subtracted from the measured concentration. For some sites this gives a jump in the time series from higher to lower concentrations. It has been investigated if older data can be corrected and more information about this available in the Swedish report "Bakgrundskorrigering av fosfatfosfor" (Background correction of phosphate-P)". The report suggest a correction of older phosphate values similar to the one used today in the chemical analysis. 

Report (in Swedish) about method comparison while changing to the Gallery instrument (Metodjämförelse vid byte till Gallery).

Current methods of measurement

Discrete analysis, photometric

Valid since June 2014
Method: ISO 15923-1:2013
Instrument: Gallery

Low concentrations

Valid since March 2019
Metod: SS-EN ISO 15681-2:2018 mod. QuAAtro method Q-064-05 Rev. 8.
Instrument: QuAAtro.

Previous methods (autoanalyzer)

2016 05 - 2019 02 (only selected samples)
Method: Bran*Luebbe Method No. G-175-96 Rev. 15 (Multitest MT 18).
Instrument: Bran*Luebbe Autoanalyzer 3.
Note: No conservation of water samples. The analyses with the autoanalyzer were only made for some samples with a concentration lower than the reporting limit of the Gallery instrument (4 µg/l). The autoanalyzer had a reporting limit of 1 µg/l.

2000-01 – 2014-05
Method: Bran & Leubbe Method No. G-175-96 2nd ed.
Instrument: Bran & Leubbe Autoanalyzer 3.
NB: No conservation of water samples.

1997-01 – 1999-12
Method: Swedish Standard SS 02 81 26-2 modified for autoanalyser.
Instrument: Technicon Autoanalyzer II.
NB: No conservation of water samples.

1987-01 – 1996-12
Method: Schuster, H. H.: 1969. Arch. Hydrobiol. 65:4. Koroleff, F. ICES C.M. 1968, C33.
Instrument: Technicon Autoanalyzer II.
NB: Water samples conserved with HgCl₂.

1969-01 – 1986-12
Method: Schuster, H. H.: 1969. Arch. Hydrobiol. 65:4. Koroleff, F. ICES C.M. 1968, C33.
Instrument: Technicon Autoanalyzer I.
NB: Water samples conserved with HgCl₂.

1965-01 – 1968-12
Method: Proctor, C. & Hood, D. W., 1954. Journal of Marine Research. Vol. 13. No. 1. Modified for autoanalyser.
Instrument: Technicon Autoanalyzer 1.
NB: Water samples conserved with HgCl₂.