On-line technique to determine the isotopic composition of total dissolved nitrogen.
A new on-line analytical setup for 15N measurements of total dissolved nitrogen (TDN) has been developed through the coupling of a high-temperature catalytic (Ce(IV)O2) oxidation furnace, a Cu reduction furnace, and an isotope ratio mass spectrometer. The detection limit for accurate delta15N measurements is 20 mg of N L-1. For N-containing compounds dissolved in water, a standard deviation on N concentration measurements of 0.2 mg of N L-1, independent of N concentration, has been found. Reproducibility on delta15N increased with increasing N concentration, with standard deviations varying from 0.8 to 0.1 per thousand in the range of 20-100 mg of N L-1. Salt matrixes, in which the N species might be dissolved, could influence the analysis capacity and continuity, mainly at concentrations above 0.1 M. To our knowledge, this system is the first successful on-line setup capable of performing routine delta15N and N concentration measurements of the TDN pool. Potential applications are large and are believed to result in an increased insight in N cycling and dissolved organic nitrogen behavior in terrestrial and aquatic ecosystems.
Huygens
Dries
D
Laboratory of Applied Physical Chemistry ISOFYS, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium. Dries.Huygens@UGent.be
Boeckx
Pascal
P
Vermeulen
Jan
J
De Paepe
Xavier
X
Park
Andrew
A
Barker
Sam
S
Van Cleemput
Oswald
O
D017753:Ecosystem; D009584:Nitrogen / Q000032:analysis* / Q000737:chemistry; D009587:Nitrogen Isotopes / Q000737:chemistry; D009862:Online Systems / Q000295:instrumentation*; D011189:Potassium Chloride / Q000737:chemistry; D015203:Reproducibility of Results; D012996:Solutions; D014867:Water / Q000737:chemistry
D009587:Nitrogen Isotopes; D012996:Solutions; D014867:Water; D011189:Potassium Chloride; D009584:Nitrogen