Second-derivative spectrometric determination of urea in milk using the diacetyl monoxime reagent.

The application of derivative spectrometry to resolve overlapping spectra and improve the sensitivity and selectivity of the colorimetric determination of urea in milk using diacetyl monoxime is presented. With first-derivative (1D) spectrometry, the lambda(max) of the colored complex was established to be 525 nm. The absorption band at lambda(max) = 525 nm in normal absorption (0D) spectrometry was resolved into three clearly distinct spectral bands with minima at 497, 530, and 566 nm with second-derivative (2D) spectrometry.