doi:

DOI: 10.3724/SP.J.1140.2013.06173

Marine Geology & Quaternary Geology (海洋地质与第四纪地质杂志) 2013/33:6 PP.173-177

A METHOD TO EXTRACT AMMONIUM AND NITRATE FROM FRESHWATER FOR NITROGEN ISOTOPE ANALYSIS


Abstract:
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.

Key words:nitrogen isotope,ammonium,nitrate ion exchange resin

ReleaseDate:2016-08-31 18:47:08



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