ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Discussion blank of nitrate during isotopic analysis of oxygen and nitrogen by the ion exchange method

Shaojie Yao, Jing Hu, Yuliang Li, Zhoufeng Wang, Kaili Yang, and Weiguo Liu

School of Water and Environment, Chang’an University, Xi’an, China

E-mail: hujing@ieecas.cn

Received: 6 December 2024  Accepted: 1 January 2026

Abstract:

Ion exchange is a traditional method for treating nitrate nitrogen and oxygen isotopes in surface water, and experimental blanks in the ion exchange process have a strong impact on nitrate isotope determination. The blanks can come from the reagents, the environment, the resin. This paper discusses the blanks and how to reduce blanks in three aspects. The results showed that: (1) the nitrate nitrogen content of 120 ml of 0.25 mol/l (M) KCl and 0.25 M NaCl was about 1.21 and 1.14 µg, and the nitrogen content could be reduced to less than 0.64 µg after burnt in a muffle furnace; (2) Nitrate nitrogen was limited to less than 0.33 µg in the determination of the environmental background blank, which was controlled by airtight equipment. (3) In particular, we found that the nitrate nitrogen content in 1 ml of resin was about 30 µg, the nitrogen content of 1 ml of resin could be reduced to 9 µg by overnight HCl soaking, and the nitrate nitrogen content of resin could be reduced to less than 0.15 µg/ml after pre-cleaning the resin by 120 ml of 0.25 M KCl or 0.25 M NaCl. This paper provides a more accurate pretreatment method for nitrate samples by ion exchange.

Keywords: Ion exchange method; Nitrate blank; Reagent blank; Resin blank

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-026-04641-8

Chemical Papers 80 (4) 3683–3691 (2026)