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The Effect of Calcium and Magnesium on Soil Nitrate Determination by Automated Segmented‐flow Methods
Author(s) -
Ananth S.,
Moraghan J. T.
Publication year - 1987
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1987.03615995005100030020x
Subject(s) - autoanalyzer , chemistry , hydrazine (antidepressant) , magnesium , sulfate , aqueous solution , chromatography , ultrafiltration (renal) , nitrate , soil water , soil science , geology , organic chemistry
An automated procedure, involving the reduction of NO ‐ 3 to NO ‐ 2 by an alkaline solution of hydrazine sulfate containing traces of Cu 2+ , is commonly used for determination of small quantities of NO ‐ 3 ‐N in electro‐ultrafiltration (EUF) extracts of soils. When this reduction method was employed to determine NO ‐ 3 ‐N in aqueous extracts from certain Calciaquolls, low and erratic results were obtained with 24 of 46 soil samples. The problem extracts contained high levels of Ca 2+ and Mg 2+ that interfered with the method. Soil extracts with <40 mg Ca 2+ L −1 and 15 mg Mg 2+ L −1 presented no analytical problems. Placement of a cation exchange resin column between the sampler and pump of a Technicon AutoAnalyzer II overcame the interference, due presumably to removal of Ca 2+ and Mg 2+ from the flow line. Solution studies revealed that Ca 2+ and especially Mg 2+ prevented quantitative reduction of NO ‐ 3 to NO ‐ 2 . No analytical problems were encountered with any of the soil extracts when a Cd‐Cu column was used to reduce NO ‐ 3 to NO ‐ 2 . Any hydrazine sulfate reduction method should be carefully evaluated when newly introduced as an analytical procedure for soil NO ‐ 3 ‐N determination.