A simple method for plasma total vitamin C analysis suitable for routine clinical laboratory use.
BACKGROUND
In-hospital hypovitaminosis C is highly prevalent but almost completely unrecognized. Medical awareness of this potentially important disorder is hindered by the inability of most hospital laboratories to determine plasma vitamin C concentrations. The availability of a simple, reliable method for analyzing plasma vitamin C could increase opportunities for routine plasma vitamin C analysis in clinical medicine.


METHODS
Plasma vitamin C can be analyzed by high performance liquid chromatography (HPLC) with electrochemical (EC) or ultraviolet (UV) light detection. We modified existing UV-HPLC methods for plasma total vitamin C analysis (the sum of ascorbic and dehydroascorbic acid) to develop a simple, constant-low-pH sample reduction procedure followed by isocratic reverse-phase HPLC separation using a purely aqueous low-pH non-buffered mobile phase. Although EC-HPLC is widely recommended over UV-HPLC for plasma total vitamin C analysis, the two methods have never been directly compared. We formally compared the simplified UV-HPLC method with EC-HPLC in 80 consecutive clinical samples.


RESULTS
The simplified UV-HPLC method was less expensive, easier to set up, required fewer reagents and no pH adjustments, and demonstrated greater sample stability than many existing methods for plasma vitamin C analysis. When compared with the gold-standard EC-HPLC method in 80 consecutive clinical samples exhibiting a wide range of plasma vitamin C concentrations, it performed equivalently.


CONCLUSIONS
The easy set up, simplicity and sensitivity of the plasma vitamin C analysis method described here could make it practical in a normally equipped hospital laboratory. Unlike any prior UV-HPLC method for plasma total vitamin C analysis, it was rigorously compared with the gold-standard EC-HPLC method and performed equivalently. Adoption of this method could increase the availability of plasma vitamin C analysis in clinical medicine.
Lady Davis Institute for Medical Research and Department of Medicine, McGill University and Jewish General Hospital, 3755 Cote Sainte Catherine, Montreal, QC, H3T 1E2, Canada.
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L
Robitaille
Lady Davis Institute for Medical Research and Department of Medicine, McGill University and Jewish General Hospital, 3755 Cote Sainte Catherine, Montreal, QC, H3T 1E2, Canada. l.hoffer@mcgill.ca.
L John
LJ
Hoffer
D001205:Ascorbic Acid / Q000097:blood*; D001774:Blood Chemical Analysis / Q000379:methods*; D002851:Chromatography, High Pressure Liquid; D006801:Humans; D009752:Nutritional Status; D015203:Reproducibility of Results; D014815:Vitamins / Q000097:blood*
D014815:Vitamins; D001205:Ascorbic Acid
Ascorbic acid; Ascorbic acid deficiency; Avitaminosis; Dehydroascorbic acid; Malnutrition; Vitamin C