Urease inhibitory activity associated with N-( n-butyl)thiophosphoric triamide is due to formation of its oxon analog

HPLC-purified N-( n-butyl)thiophosphoric triamide (NBPT) had no delectable urease inhibitory activity when tested with jack bean urease. However, considerable inhibition was associated with soil extracts when NBPT had been exposed in the soils for several hours. This activity was due to an NBPT derivative that was isolated by reverse phase HPLC. with NBPT and the derivative detected by a postcolumn system based on acid hydrolysis and phosphomolybdate complex formation. The purified derivative was shown to be highly active, giving 50% inhibition of jack bean urease at a concentration between 10 and 100 nM. Mass spectral analysis revealed the active derivative to be N-( n-butyl) phosphoric triamide. the oxon analog of NBPT.