0 ml of EBC was obtained in which the following indices were detected: Total protein content (g/L) by Lowry's method, EBC proteolytic activity by the lysis of albumin, azocasein, and azocollagen by Veremeyenko's method, the content of aldehyde and ketone derivatives of 2,4-dinitrophenylhydrazone
(AKDNPH) of the main and neutral character by Dubinina's method, the content of nitrogen monoxide metabolites (NMON) by Yemchenko's method (1994) in Gozhenko's modification (2002), total, enzymatic, and non-enzymatic fibrinolytic activity by Kukharchuk's method.
However, it is clearly apparent that most of reported spectrophotometric researches in the literature either employed 2,4-dinitrophenylhydrazone (Schwimmer and Weston's procedure)  or salicylaldehyde (Straub's procedure)  with continues modifications and improvements.
2% w/v stock solution of 2,4-dinitrophenylhydrazone (Merck, USA) was prepared by dissolving the appropriate weight in 250 ml of HCL 1 M.
In brief, proteins precipitated with trichloroacetic acid were suspended and incubated in a solution containing 10 mM 2,4-dinitrophenylhydrazones
(DNPH) and 2 N HCl for 1 hour at 15 C.
HPLC-DAD analysis of ketones as their 2,4-dinitrophenylhydrazones
in Brazilian sugarcane spirits and rum.
Determination of nanogram amounts of carbonyls as 2,4-dinitrophenylhydrazones
by high-performance liquid chromatography.