Total Nitrogen by Alkaline Persulfate Digestion and Enzymatic Nitrate Analysis

Building Consensus Methods to Support Environmental Laboratories
Oral Presentation

Prepared by E. Campbell, A. Marceau, W. Campbell, T. Kinnunen-Skidmore
NECi, 334 Hecla Street, at 217 Calumet St, Lake Linden, MI, 49945, United States


Contact Information: ellenr@nitrate.com; 906.296.1000

ABSTRACT

NECi develops recombinant enzymes for green analytical chemistry. Enzymes catalyze difficult chemical reactions under gentle conditions in complex matrices. Numerous common lab methods can be done with nonhazardous reagents and low cost instrumentation when the methods are enzyme-based.

Manual formats of nitrate reductase (AtNaR) for nitrate analysis were adopted as 4500-NO3-J by standardmethods.org in Fall 2019. NECi’s nitrate reductase reagent has standard method status for autoanalyzers under CWA and ASTM International, and for discrete analyzers under SDWA. The new alkaline persulfate method for Total Nitrogen drives all N compounds to nitrate. In order to extend applications of the method, NECi ran internal validation studies to determine whether its AtNaR reagents were compatible with this new way to determine TN. Lab formats, where the color reagent step includes an aggressive acid, and NECi’s onsite test kits, with less aggressive citric acid, were tested. All formats are shown to produce reliable, accurate results. In addition, the paper describes a safe and effective method for the sample digestion step. The publication shows that an off the shelf IntantPot™ or similar pressure cooker device can be used in place of an autoclave or heating block. This puts TN in reach of Citizen Scientists and other users with limited lab facilities.

Citation: On 24Jan20, status of the paper is prepublication. This was posted on MethodsX on 16Jan20, at this link: https://doi.org/10.1016/j.mex.2020.100791