Nitrate nitrogen and oxygen isotopes have been widely used to trace the nitrogen biogeochemical cycle by identifying NO(3)(-) sources. An improved method of anion exchange was developed to measure delta(15)N-NO(3)(-) in fresh water by continuous-flow elemental analyzer/isotope ratio mass spectrometry (EA-IRMS). We used a custom-built exchange resin column, a peristaltic pump and the oven-drying method in our experiments. Consequently, the amount of Ag(2)O used as a neutralizer was reduced, time was saved, and operation became simpler than before. Meanwhile, analytical precision remained identical to previous studies. KNO(3) solutions were prepared at 0.2, 5 and 25 mg-N L(-1) from KNO(3) standard salt (delta(15)N = +6.27 parts per thousand), and the average delta(15)N values of the solutions after having been absorbed on and subsequently stripped from anion columns were +6.62 +/- 0.22 parts per thousand (n = 6), +6.38 +/- 0.09 parts per thousand (n = 6), and +6.26 +/- 0.07 parts per thousand (n = 6), respectively. In addition, the "natural" water sample delta(15)N-NO(3)(-) showed consistency in comparison to standards, and the mean standard deviation by the different approaches was 0.08 parts per thousand. Accordingly, by these improvements the anion exchange resin technique is demonstrated to be more suitable for measuring delta(15)N in NO(3)(-) than original techniques. (C) 2010 Elsevier B.V. All rights reserved.