Comparison of ascorbic acid concentrations in whole blood obtained by venipuncture or by finger prick.

Vitamin C (ascorbic acid) concentrations in whole blood obtained by finger prick or by venipuncture have been shown to be equivalent when measured by the 2,4-dinitrophenylhydrazine procedure. Whole blood obtained by eithertechnique is stable for at least 6 h at 25#{176}C, and for as long as 28 days when stabilized with trichloroacetic acid and stored at 4#{176}C. Storage of whole blood at -70#{176}C is accompanied by an initial loss (10-20%) of vitamin C; however, additional losses of vitamin C do not occur beyond the third day of storage.