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Errors in Concentrating Ammonium Samples Prior to Isotope‐Ratio Analysis
Author(s) -
Reeder J. D.
Publication year - 1984
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1984.03615995004800030047x
Subject(s) - fractionation , chemistry , boric acid , evaporation , dissolution , contamination , ammonia , analytical chemistry (journal) , chromatography , nuclear chemistry , ecology , physics , organic chemistry , biology , thermodynamics
Errors during 15 N analysis can result from NH + 4 ‐N loss, isotopic fractionation, or atmospheric contamination during the distillation and concentration of samples prior to mass spectrometric analysis. The effectiveness of three trapping acids were compared at two different evaporation temperatures for their capacity to rapidly and efficiently concentrate large numbers of samples with minimum error in 15 N measurements due to fractionation or contamination. Standard samples containing 1 mg of N as either (NH 4 ) 2 SO 4 or NH 4 Cl, at 15 N concentrations of 0.366, 3, or 10 atom %, were acidulated with one of three trapping acids (2 mL of 0.1 M HCL; 2 mL of 0.04 M H 2 SO 4 ; or 2 mL of 0.04 M H 2 SO 4 + 2 mL of 2% H 3 BO 3 ) and evaporated to dryness on either a 95°C waterbath or an 87°C dry‐bath. Significant fractionation errors occurred in samples acidulated with HCl when the evaporation procedure was prolonged and a film of NH 4 Cl was allowed to form on the walls of sample vials. Samples acidulated with H 2 SO 4 were significantly contaminated with atmospheric ammonia when the evaporation procedure was prolonged. The presence of boric acid in evaporating samples resulted in erratic 15 N values which were thought to be partially due to incomplete dissolution of the samples prior to mass spectrometric analysis.