New kinetic method for creatinine measurement now automated in the Cobas Fara centrifugal analyzer.

A new kinetic method to determine creatimne in serum by using an alkaline 3,5-dinitrobenzoate solution was recently reported (1). Interference from pseudo-creatinine chromogens, bilirubin, or triacylglycerols was negligible. The results obtained with this kinetic spectrophotometric assay, performed with an Eppendorf ACP 5040 analyzer, agreed well with the procedure of Jaff#{233}, as modified by Helger et al. (2). The procedure, however, requires that the changes in absorbance be measured in very short time intervals after the start of the reaction. We have automated this procedure (1) for determination of serum creatimne for use with a Cobas Fara centrifugal analyzer (F. Hoffmann-La Roche, Basle, Switzerland). The reagents consist of (a) 0.3 mol/L solution of 3,5-dimtrobenzoic acid (Carlo Erba, Milano, Italia; cat. no 405274) in 0.3 molfL NaOH and (b) 0.5 mol/L NaOH. The instrument settings were as follows: