title: Plasma ascorbic acid preparation and storage for epidemiological studies using TCA precipitation.
abstract: OBJECTIVE
  To introduce a procedure to validate an ascorbic acid method using trichloroacetic acid (TCA) for plasma stabilization at different storage temperatures.
  
  
  METHODS
  EDTA and heparin plasma were precipitated with TCA (1:5) containing 0.54 mol/L EDTA, or without. Samples were stored at -20 degrees C and -70 degrees C and their stability was tested at room temperature for 24 h.
  
  
  RESULTS
  A significant 40% loss (p<0.001) of plasma ascorbic acid was found when EDTA samples with added EDTA were stored at -20 degrees C for 2-4 weeks compared with storage at -70 degrees C. Ascorbic acid in heparin plasma without added EDTA was most unstable and samples left at room temperature for 24 h lead to almost a total loss of ascorbic acid. Addition of EDTA to the TCA solution improved stability of samples of both plasma types at room temperature.
  
  
  CONCLUSIONS
  The recommended procedure for ascorbic acid determination in plasma stabilized with TCA is immediate storage at -70 degrees C and inclusion of EDTA into the TCA solution.
authors: Department of Health and Functional Capacity, Biomarker Laboratory, National Public Health Institute, Helsinki, Finland. irma.salminen@ktl.fi
authors: Irma
authors: I
authors: Salminen
authors: Georg
authors: G
authors: Alfthan
mesh_terms: D001205:Ascorbic Acid / Q000032:analysis / Q000097:blood*; D001793:Blood Preservation / Q000379:methods* / Q000592:standards; D001800:Blood Specimen Collection / Q000379:methods / Q000592:standards; D011232:Chemical Precipitation; D004492:Edetic Acid / Q000032:analysis / Q000097:blood; D016021:Epidemiologic Studies; D005260:Female; D006801:Humans; D008297:Male; D013048:Specimen Handling / Q000379:methods / Q000592:standards; D014238:Trichloroacetic Acid / Q000097:blood* / Q000378:metabolism
chemical_list: D014238:Trichloroacetic Acid; D004492:Edetic Acid; D001205:Ascorbic Acid