High-performance liquid chromatographic determination of plasma ascorbic acid in relationship to health care.

We have developed a simple reversed-phase high-performance liquid chromatographic method for determining plasma ascorbic acid level and studied the relationship between its plasma concentration and fruit and vegetable intake and plasma dopamine-beta-hydroxylase activity. The samples were pretreated by precipitating the proteins and injected onto the column. Elution with a methanol gradient in sodium phosphate buffer was carried out by monitoring the absorbance at 265 nm, and the peak corresponding to ascorbic acid was well separated from other peaks of reagents used for pretreatment and from plasma endogenous components. The proposed method correlated well with the conventional dichlorophenol-indophenol method. Mean levels of ascorbic acid in normal human plasma were 0.86 +/- 0.36 mg/dl for males (twenty subjects, 19-28 years old) and 1.01 +/- 0.30 mg/dl for females (twenty subjects, 19-21 years old). There was good correlation between plasma ascorbic acid levels and dopamine-beta-hydroxylase levels, reflecting activities of daily living, but no correlation was found between these levels and dietary consumption of vegetables or fruits.