Fluorine (F)

Atomic number: 9
Atomic weight: 18.9984
Average concentration in ocean: 68 µmol/kg
Residence time: 500,000 years

Distribution in ocean
Fluorine is a major component of seawater and is believed to have a conservative distribution, although positive anomalies have been reported in several studies (data).

Speciation
Fluoride is present in seawater as the fluoride anion F-.

Analysis
Fluoride can be determined colorimetrically by the llanthanum-alizarium complexone method or potentiometrically with a fluoride ion selective electrode that has been calibrated in seawater media.

References