(Seborin, Schwarzkopf). The treatment consisted of a skin massaging with the lotion during 1 min. The left side was not treated. Collection of hair specimens of both sides was done 1 day before hair treatment, 1 week and 1 month after treatment (for 5 subjects also after 2 months of treatment). A 3 cm proximal hair segment (if available) was analyzed.
2.3. Sample preparation and extraction method
The method used for extraction of the hair samples has been described previously [10]. In this study 2 ng of EtG-D5 was added as internal standard and the derivatization agent was heptafluorobutyric anhydride (HFBA). The observed precursor ions were: m/z 596, 397 for EtG and m/z 601 for EtG-D5. The actual limit of detection (LOD) was at 0.5 pg/mg and the lowest limit of quantification (LLOQ) was at 1.5 pg/mg. The hair lotions used in our study were tested for EtG by diluting them 100 and 200 times in water. The 2 aqueous solutions were then analyzed using the same extraction and quantification method as previously described.