抄録
Ascorbic acid (AH2) is well known to give false positive errors in the determination of hydrogen peroxide (H2O2) with the catalase-Hantzsch reaction which involves the formation of formaldehyde from H2O2 and methanol, followed by the color development based on the condensation reaction of formaldehyde formed and acetylaceton added in the presence of ammonium ion.
Present study was undertaken to elucidate a possible mechanism of the AH2 interference in the H2O2 determination. Dehydro-ascorbic acid (DA) was prepared by use of immobilized ascorbate oxidase-tube. The oxidation-reduction relationship between AH2 and DA was investigated with spectral analysis and using the Hantzsch reaction and aldehyde dehydrogenase reaction.
1.AH2 continuously increases the color development of the catalase-Hantzsch reaction in the absence of H2O2, suggesting the formation of H2O2 or formaldehyde in the reaction mixture.
2.AH2 is oxidized by a sparing amount of oxygen and Cu2+ to form H2O2 and DA.
3.DA formed reacts with methanol even in the absence of catalase to regenerate AH2 and formaldehyde. H2O2 reacts with methanol in the presence of catalase to form formaldehyde. The formaldehyde increases the color development of the Hantzsch reaction.
4.AH2 regenerating system (AH2, O2 and methanol) continuosly supplies H2O2 and formaldehyde which are used as substrates of the catalase-Hantzsch reaction and then increase the color development. The coupled reaction of DA reduction (DA to AH2) and methanol oxidation (methanol to formaldehyde) seems to play a most important role in AH2 interference.
