Validation of a micromethod for determining oxidized and reduced vitamin C in plasma by HPLC-fluorescence.
An HPLC micro-method with fluorescence detection has been developed to determine total vitamin C (vit C) and dehydroascorbic acid (DHA) concentrations in human plasma samples. This method is based on the rapid, specific reaction of DHA with dimethyl-o-phenylenediamine (DMPD) to form a fluorescent quinoxaline derivative that is quantified by HPLC in less than 5 minutes. The method was assessed with reference to the direct 2,4-dinitrophenylhydrazine (DNPH) colorimetric method. They were well correlated (r3 = 0.879), but the DMPD-HPLC method had the limit of detection 6 times lower than the standard method and the relative error for a vitamin standard was 10 times better than that of the standard method. The plasma DHA to total vit C ratio varied from 10 to 60%, depending on sample processing. Plasma that were immediately analysed contained 10% DHA whatever the subject's age; frozen deproteinized samples kept 1 week (-67 degrees C) had 20%, and blood samples kept for one hour at room temperature before treatment had up to 60% DHA. The ratio in capillary samples taken from the finger was 11-42%. This rapid, specific and very sensitive micro-method is well suited to routine measurements of plasma vit C.
Tessier
F
F
Institut National Agronomique, Laboratoire de Chimie Analytique, Paris - France.
Birlouez-Aragon
I
I
Tjani
C
C
Guilland
J C
JC
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001205:Ascorbic Acid / Q000097:blood*; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D003124:Colorimetry; D003683:Dehydroascorbic Acid / Q000032:analysis* / Q000737:chemistry*; D005470:Fluorometry; D006801:Humans; D016014:Linear Models; D008875:Middle Aged; D010084:Oxidation-Reduction; D010655:Phenylenediamines / Q000737:chemistry*; D010659:Phenylhydrazines / Q000737:chemistry; D012015:Reference Standards; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D018709:Statistics, Nonparametric; D013696:Temperature; D013997:Time Factors
D010655:Phenylenediamines; D010659:Phenylhydrazines; C004787:2,4-dinitrophenylhydrazine; C004781:dimethyl-4-phenylenediamine; D001205:Ascorbic Acid; D003683:Dehydroascorbic Acid