Stability of nitroblue tetrazolium-based alkaline phosphatase substrates

This report demonstrates the stability of NBT substrate after multiple expo sures to alkaline phosphatase. Perhaps more important than the ability to r euse substrates, the report provides some insight into the mechanisms by wh ich tetrazoliums are reduced and evidence for the formation of an intermedi ary product, i.e., a half-formazan that is reduced more rapidly.