Marine Geology & Quaternary Geology (海洋地质与第四纪地质杂志) 2013/33:6 PP.173-177
This paper presents a simple and rapid method to concentrate ammonium and nitrate from freshwater samples for an on-line isotope analysis using an elemental analyzer coupled to a mass spectrometer.Ammonium and nitrate are collected by passing the water-sample through pre-filled,disposable,ion exchanging resin columns.The ammonium and nitrate in sample solutions are separated as ammonium into diluted H2SO4by sequential distillation techniques.Then,the excrescent SO2-4in the distillate is precipitated directly as an insoluble salt of BaSO4.(NH4)2SO4is collected by freezing-drying filtrate,which is subsequently combusted in an elemental analyzer forδ15 N determination.The sorption efficiency of 001×7cationic resin and 732cationic resin for 2Lsample solutions with ammonium and nitrate concentration of0.5,1.0,5.0mg/L is95.1%,elution recovery is95%,showing insignificant isotope fractionation during precipitation.Analyses of the solutions prepared from(NH4)2SO4and KNO3distributed,and also the rain,river,lake and well samples showed that the method can produce good quality of isotope measurements.
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