Measurement of dehydrogenase activity using 2-p-iodophenyl-3-p-nitrophenyl-5-phenyltetrazolium chloride (INT) in the presence of copper

This paper reports on the adverse effect of Cu on the use of 2-p-iodophenyl-3-p-nitrophenyl-5-phenyltetrazolium chloride (INT) as a substrate for measuring microbial dehydrogenase activity (DHA). The presence of Cu affected the absorbance of the reaction product 2-p-iodophenyl-3-p-nitrophenyl-5-phenyltetrazolium formazan. The experiment provides evidence that the use of INT is an unreliable measure of DHA activity in soils contaminated with Cu.