Inclusion Of Nitrate And Nitrite In The Kjeldahl Nitrogen Determination Of Soils And Plant Materials Using Sodium Thiosulphate

Abstract

Sodium thiosulphate was used in a modification of the regular Kjeldahl method for the determination of total N in soil and plant samples containing NO3-N and NO9-N. Quantitative recoveries of added 15N-labelled and unlabelled N3-N (1000 pg N), NO2--N (500 pg N), and N3--N (500 pg N) + N2--N (250 pg N) were obtained from soils, plant materials and adenine, even in the presence of water (up to 50 ml H2O/sample) when 5 g of Na2S2O3.5H2O as 25% aqueous solution was added to each sample before digestion. Moreover, this procedure does not require additional pretreatment of samples as does the salicylic acid-sodium thiosulphate or KMn04-Fe modification of the Kjeldahl method, and therefore saves considerable time. © 1984, Taylor & Francis Group, LLC. All rights reserved.