Development of an UHPLC–MS/MS method to determine cutaneous biodistribution of cannabidiol after topical application of cannabidiol gel assisted by iontophoresis

Cannabidiol has potential for use in skin disease therapy, so it is important to know the cutaneous biodistribution of cannabidiol after topical application of cannabidiol formulations. However, currently existing quantification methods for the investigation of cannabidiol skin distribution are not optimal. This study aimed to establish a method for the determination of cannabidiol in skin samples by UHPLC–MS/MS. A BEH C 18 (50.0 × 2.1 mm, 2.5 μm) column was used; the mobile phase consisted of acetonitrile–0.1% formic acid (70:30, v/v), the flow rate was 0.2 μl·min −1 and the column temperature was 30°C. Positive‐ion mode with multiple reaction monitoring detection was used to quantify cannabidiol ( m/z 315.1 → 193.1) while diphenhydramine ( m/z 256.3 → 167.08) served as the internal standard. Good linearity was shown in the range of 1–200 ng·ml −1 for cannabidiol with correlation coefficients of >0.999. The LLOQ was 1 ng·ml −1 . The intra‐day and inter‐day RSDs of cannabidiol were all