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An improved fluorescence method for the determination of nanomolar concentrations of ammonium in natural waters
Author(s) -
Jones Ronald D.
Publication year - 1991
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.1991.36.4.0814
Subject(s) - microporous material , fluorescence , ammonium , chemistry , reagent , detection limit , environmental chemistry , chromatography , analytical chemistry (journal) , organic chemistry , physics , quantum mechanics
An improved fluorescence method is described for measuring nanomolar concentrations of NH 4 + in natural waters. This method is based on the conversion of NH 4 + to NH 3 and subsequent diffusion of NH 3 across a microporous hydrophobic Teflon membrane into a flowing stream of o ‐phthaldialdehyde reagent to produce a fluorescent adduct. The product is detected fluorometrically with a lower detection limit of better than 1.5 nM. Up to 30 determinations h −1 can be made. The method works well in freshwater or salt water. Field tests of the method in the Dry Tortugas and Gulf Stream gave NH 4 + concentrations that ranged from 18.0 nM in Gulf Stream waters to 2,254.7 nM in interstitial waters from coralline reef sands. The method can be used to measure near real‐time NH 4 + concentrations in situations where it was previously difficult or impossible.