Ultra-high-performance liquid chromatography–tandem mass spectrometry measurement of climbazole deposition from hair care products onto artificial skin and human scalp

A sensitive and specific ultra-high-performance liquid chromatography–tandem mass spectrometry (UHPLC–MS/MS) method was developed and validated for the measurement of climbazole deposition from hair care products onto artificial skin and human scalp. Deuterated climbazole was used as the internal standard. Atmospheric pressure chemical ionization (APCI) in positive mode was applied for the detection of climbazole. For quantification, multiple reaction monitoring (MRM) transition 293.0 > 69.0 was monitored for climbazole, and MRM transition 296.0 > 225.1 for the deuterated climbazole. The linear range ran from 4 to 2000 ng mL−1. The limit of detection (LOD) and the limit of quantification (LOQ) were 1 ng mL−1 and 4 ng mL−1, respectively, which enabled quantification of climbazole on artificial skin and human scalp at ppb level (corresponding to 16 ng cm−2). For the sampling of climbazole from human scalp the buffer scrub method using a surfactant-modified phosphate buffered saline (PBS) solution was selected based on a performance comparison of tape stripping, the buffer scrub method and solvent extraction in in vitro studies. Using this method, climbazole deposition in in vitro and in vivo studies was successfully quantified.