title: An automated, specific, spectrophotometric method for measuring ascorbic acid in plasma (EFTSA).
abstract: OBJECTIVE
  To evaluate an automated enzyme linked, ferric-tripyridyltriazine spectrophotometric assay (EFTSA) for plasma ascorbic acid.
  
  
  METHODS
  Using aqueous ascorbic acid solutions and plasma containing native and/or added ascorbic acid, the following were assessed: reaction kinetics, dose response relationships, recovery of added ascorbic acid, specificity, precision.
  
  
  RESULTS
  Performing the test on a Cobas Fara centrifugal analyser, the test is linear at least to 400 micromol/L; within-run CVs at 20, 50, 140, and 300 micromol/L ascorbic acid, in both pure aqueous solutions and in plasma, were <5.5%; 99-105% of added ascorbic acid (from 30-130 micromol/L) was recovered. The reaction of ascorbic acid is virtually instantaneous; other native antioxidants do not appear to interfere, and there is no interference by dehydroascorbic acid when readings are taken within a 15-60-s reaction time window.
  
  
  CONCLUSIONS
  EFTSA appears suitable for the routine measurement of ascorbic acid in plasma.
authors.affiliation: Department of Health Sciences, Hong Kong Polytechnic University, Hong Kong.
authors.forename: I F
authors.initials: IF
authors.lastname: Benzie
mesh_terms: D000328:Adult; D000975:Antioxidants / Q000032:analysis; D001204:Ascorbate Oxidase; D001205:Ascorbic Acid / Q000097:blood*; D001774:Blood Chemical Analysis / Q000379:methods* / Q000706:statistics & numerical data; D004355:Drug Stability; D005069:Evaluation Studies as Topic; D005290:Ferric Compounds; D006801:Humans; D010084:Oxidation-Reduction; D012680:Sensitivity and Specificity; D013053:Spectrophotometry / Q000379:methods* / Q000706:statistics & numerical data; D014527:Uric Acid / Q000097:blood
chemical_list: D000975:Antioxidants; D005290:Ferric Compounds; D014527:Uric Acid; D001204:Ascorbate Oxidase; D001205:Ascorbic Acid