Refining measurement techniques for N2H4, NH2OH, and NH4+-N in nitrogen-rich environments: Mitigating interference for accurate detection

Abstract

In biological studies, several nitrogenous compounds interfere with each other’s measurements, which may result in unreliable results and misinterpretation. In this context, this study aims to refine the analytical techniques for N₂H₄, NH₂OH, and NH₄⁺-N by eliminating interferences to obtain accurate data from the anammox system as a case study. Results indicated that NO₂^--N interferes with N₂H₄ and NH₂OH measurements, while N₂H₄ and NH₂OH interfere with NH₄⁺-N measurements. In N₂H₄ determination, different NO₂^--N levels resulted in different utilization of sulfamic acid (SA) in terms of volume and concentration. The samples containing ≤ 2 mg/L NO₂^--N were pretreated with 400 µL 0.5 % SA to prevent NO₂^--N interference, while 10 % SA is required for NO₂^--N concentrations between 27.25 mg/L and 46.62 mg/L. The 10 % SA treatment also significantly mitigated NH₂OH degradation in solutions, ensuring precise and steady results even in the presence of NO₂^--N. Adding 0.1 g of KIO₃ to 50 mL of samples containing N₂H₄ (≤ 10 mg/L) produced findings most comparable to the control group in NH₄⁺-N tests. Furthermore, without any pretreatment, it is possible to measure NH₄⁺-N accurately if the NH₂OH concentration is ≤ 0.01 mM. Overall, this study offers insightful data for further biological research in nitrogen-rich environments.