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 damage in human skin which could lead to cutaneous disorders such as premature aging or skin cancer. The aim of this work was to assess AA concentrations in human dermis by a microdialysis technique associated with gas chromatography-mass spectrometry (GC-MS). Due to the non-volatility of AA, it was necessary to derivatize this acid. Three methods, one methylation and two silylations, were validated and compared to determine the most sensitive. To validate the methods, calibration curves were plotted from AA concentrations ranging from 34 to 500 nmol mL⁻¹. The calibration curves were linear with a good correlation coefficient (r ≥ 0.99). Repeatability and reproducibility were significant with a coefficient of variation 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, silylation was the most sensitive method to assess AA. Thus, this method was performed to determine AA concentrations in microdialysates. In order to study AA 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.