An electrospray ionization ion trap mass spectrometric (ESI-MS-MSn) study of dehydroascorbic acid hydrolysis at neutral pH.
The hydrolysis of dehydroascorbic acid (DAAH) at neutral pH and 27 degrees C was investigated by direct infusion electrospray ionisation ion trap mass spectrometry (ESI-MS). This approach permitted derivatisation and elution procedures to be avoided, reducing to the minimum extent sample manipulation and allowing a rapid and direct observation of the species involved in the reaction. Six main peaks, related to hydrated dehydroascorbate (HyDAA-) and diketogulonate (HyDKG-) anions, were observed in the mass spectra of DAAH solutions at different times of incubation and were characterised by MSn experiments. The relevant signal intensities changed with time and a model, based on the irreversible pseudo-first order HyDAA(-)-->HyDKG- conversion, fitted successfully the data obtained for dehydroascorbate. The kinetic constant of the process was (3.2 +/- 0.5) x 10(-2) min-1. The influence of metal ion traces on the hydrolysis rate was also checked, performing experiments in the presence of EDTA, and was found to be negligible.
Cioffi
N
N
Dipartimento di Chimica, Università degli Studi di Bari, 4 via E. Orabona, I-70126 Bari, Italy. cioffi@chimica.uniba.it
Losito
I
I
Terzano
R
R
Zambonin
C G
CG
D015083:2,3-Diketogulonic Acid / Q000138:chemical synthesis*; D003683:Dehydroascorbic Acid / Q000737:chemistry*; D006868:Hydrolysis; D021241:Spectrometry, Mass, Electrospray Ionization
D015083:2,3-Diketogulonic Acid; D003683:Dehydroascorbic Acid