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Nitrogen isotope analysis of ammonium and glycine

method development for aqueous solutions and soil extracts

Norlin, Elin (2005). Nitrogen isotope analysis of ammonium and glycine. Diss. (sammanfattning/summary) Umeå : Sveriges lantbruksuniv., Acta Universitatis Agriculturae Sueciae, 1652-6880 ; 2005:84
ISBN 91-576-6983-X
[Doctoral thesis]

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Stable isotope techniques can be used as a tool in nitrogen cycling studies of different ecosystems. The studies are based on measurement of the heavy (15N)- to- light (14N) isotopic ratios of nitrogen in different biospheric pools. Isotope ratio mass spectrometry (IRMS) is the most precise technique to use for analysis of nitrogen isotopic ratios. This thesis deals with the development of methods for compound-specific nitrogen isotope analysis of ammonium and glycine in aqueous solutions and soil extracts using Gas Chromatography - Combustion (GC-C) - IRMS. For ammonium, three different techniques were developed: equilibrium headspace analysis, solid phase microextraction (SPME) and the purge and trap (P & T) technique, which were all based on conversion of ammonium to ammonia with subsequent separation of ammonia for analysis. In the SPME and P & T approaches, custom-made absorbents were used for pre-concentration, followed by thermal desorption into the GC-C-IRMS system. For the equilibrium headspace technique, high precision measurements of the nitrogen isotopic ratio were obtained for concentrations above 420 mg N L-1. With further improvements and the use of suitable equipment, the method has the potential to be used for solutions containing ammonium in the low mg N L-1 range. The SPME technique increased the sensitivity by a factor of » 3 compared to the headspace technique, but was less precise. In addition, the NafionÒ material used for absorption showed a memory effect in the desorption step. With the P & T technique a large variation in the measured isotopic value was observed (using solutions containing 2 mg N L-1) which was due to a non-quantitative thermal desorption. However, with further improvements, the P & T technique has the potential to be used for samples containing below 1.0 µg N, which is a much lower amount than that possible with any method used today. A method for determination of the nitrogen isotopic ratio in free glycine in soil extracts was also developed. By a combination of sample pre-concentration and Isotope Dilution Mass Spectrometry (IDMS), it was possible to determine isotopic ratio in soil extracts with a glycine concentration of only 3 µM (0.042 mg N L-1). The precision obtained was sufficient for use with tracer studies and was higher by an order of magnitude than the precision obtained with conventional GC-MS.

Authors/Creators:Norlin, Elin
Title:Nitrogen isotope analysis of ammonium and glycine
Subtitle:method development for aqueous solutions and soil extracts
Series Name/Journal:Acta Universitatis Agriculturae Sueciae
Year of publishing :2005
Number of Pages:42
ALLI. Norlin, E., Irgum, K. and Ohlsson, K. E. A., 2002. Determination of the 15N/14N Ratio of Ammonium and Ammonia in Aqueous Solutions by Equilibrium Headspace-Gas Chromatography-Combustion-Isotope Ratio Mass Spectrometry. The Analyst 127, 735-740. II. Norlin, E., Irgum, K. and Ohlsson, K. E. A., 2003. Nitrogen Isotope Analysis of Ammonium in Aqueous Solutions Using a Perflourosulfonated Ionomer Membrane for Solid-Phase Microextraction. Rapid Communications in Mass Spectrometry 17, 936-942. III. Norlin, E., Nguyen, D., Ohlsson, K. E. A. and Irgum, K., 2005. Development of Sorption Tubes with a Sulfonated Styrene-Divinylbenzene Copolymer Surface Layer for Use in Nitrogen Isotope Analysis of Ammonium and Ammonia. Manuscript. IV. Norlin, E., Irgum, K. and Ohlsson, K. E. A., 2005. Nitrogen Isotope Analysis of Free Glycine in the Mor Layer of a Forest Soil using Isotope Dilution Mass Spectrometry. Submitted manuscript.
Place of Publication:Umeå
ISBN for printed version:91-576-6983-X
Publication Type:Doctoral thesis
Full Text Status:Public
Agris subject categories.:P Natural resources > P33 Soil chemistry and physics
Subjects:Not in use, please see Agris categories
Agrovoc terms:nitrogen, isotopes, tracer techniques, ammonium, amino acids, soil analysis, analytical methods
Keywords:nitrogen, stable isotope, isotope ratio mass spectrometry, ammonium, glycine, amino acid, solid phase microextraction, purge and trap, headspace analysis
Permanent URL:
ID Code:891
Department:(S) > Institutionen för skogsekologi (921101-930630)
Deposited By: Elin Norlin
Deposited On:22 Aug 2005 00:00
Metadata Last Modified:02 Dec 2014 10:07

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