Transdermal sampling of vitamin D3 and 25-hydroxyvitamin D3 | Bioanalysis

Aim: Transdermal analysis is proposed for vitamin D3 and its hydroxylated metabolite to overcome problems associated with blood analysis. Methods: Vitamin D3 was extracted directly from skin with solid patches and liquid phases. Deuterium-labeled vitamin D3 was added to the extraction solutions to compensate for variability and accurately determine the rate of transdermal transfer. Of the different extraction solvents tested, 50:50 octanol:isopropanol showed the best results, with an accuracy of 115% and reproducibility better than 30%. Conclusion: The research shows that transdermal route can be used for analysis of vitamin D3 in porcine skin. When microneedles are used, accurate measurements were obtained in 1 h. With intact skin, the highest accuracy was obtained when extraction was done for 2 h.