Stabilized Trinder reagent.
Spontaneous aspecific coloration in so-called Trinder reagents which can alter subsequent colorimetric determinations is inhibited by adding compounds of the chelating agent class to the solution. The resultant compositions contain a peroxidase enzyme, a phenylpyrazone derivative, a compound of phenolic or aromatic amine structure and a stabilizer. Preferred stablizers are ethylenediaminetetraacetic acid (EDTA) and diethylenetriaminepentaacetic acid (DTPA).