Stabilized alkaline picrate reagent for jaffe creatinine determination

Claim 1

An improved method for determining creatinine, comprising the following steps: preparing a stabilized alkaline picrate reagent solution by mixing water, picric acid, a molar excess relative to said picric acid of an alkali metal hydroxide, and an alcohol having 1 to 4 carbon atoms, said alcohol being employed in an amount effective to stabilize said alkaline picrate reagent solution during storage; storing said stabilized alkaline picrate reagent solution in a sealed container for a time in excess of the time an unstabilized alkaline picrate reagent solution otherwise corresponding to said stabilized alkaline picrate reagent solution but lacking said alcohol would be stable, until said stabilized alkaline picrate reagent solution is needed for a creatinine determination; combining an aliquot of said stored stabilized alkaline picrate reagent solution and an aliquot of a sample solution to be analyzed for creatinine, to produce a colored solution; and measuring the absorbance of said colored solution.