Ascorbic acid assessment in human dermis by a microdialysis technique associated with gas chromatography-mass spectrometry

Ascorbic acid (AA) plays a significant role in preventing photobiological d amage in human skin which could lead to cutaneous disorders such as prematu re aging or skin cancer. The aim of this work was to assess AA concentratio ns in human dermis by a microdialysis technique associated with gas chromat ography-mass spectrometry (GC-MS), Due to the non-volatility of AA, it was necessary to derivatize this acid. Three methods, one methylation and two s ilylations, were validated and compared to determine the most sensitive, To validate the methods, calibration curves were plotted from AA concentratio ns ranging from 34 to 500 nmol mL(-1). The calibration curves were linear w ith a good correlation coefficient (r greater than or equal to 0.99). Repea tability and reproducibility were significant with a coefficient of variati on of less than 10 %, The accuracy of the techniques was meaningful as the bias was low (ranging from -5.6 to 5.0%), According to our results, silylat ion was the most sensitive method to assess AA. Thus, this method was perfo rmed to determine AA concentrations in microdialysates. In order to study A A in human dermis, a microdialysis method was used to sample AA and the GC- MS technique used to assess this acid in the microdialysates. Microdialysis can only partially collect AA from human dermis. An ex vivo recovery of AA was 30 +/- 2% (n = 7). The average concentration of AA in microdialysates was 250 +/- 66 nmol mL(-1) (Mean +/- SD, n = 5), In view of the AA recovery , AA concentrations in human skin ranged from 759 to 891 nmol mL(-1).