High performance liquid chromatography-diode array and electrospray-mass spectrometry analysis of vardenafil, sildenafil, tadalafil, testosterone and local anesthetics in cosmetic creams sold on the Internet web sites

A simple high-performance liquid chromatography (HPLC) method with ultraviolet diode array (UV-DAD) and electrospray ionisation mass spectrometry (ESI-MS) detection has been developed for the determination of vardenafil, sildenafil, tadalafil, testosterone, procaine, lidocaine, prilocaine, and benzocaine in cosmetic creams sold as promising remedies for male erectile dysfunction and female genitals stimulation. The presence of these substances in commercial cosmetic samples is prohibited. Aliquots (1 g) of the cosmetic creams under investigation were diluted 1:100 in methanol, subjected to ultrasonic treatment, added with benzoic acid as internal standard, and analyzed by HPLC-DAD and HPLC-ESI-MS after a further 1:1000 dilution. The compounds were separated by reversed phase chromatography with water (0.02% trifluoroacetic acid) and acetonitrile gradient elution and detected by UV-DAD at 228, 255 and 290 nm and by ESI-MS positive ionisation mode. Benzoic acid was used as internal standard. Linearity was studied with UV-DAD detection from 2.5-7.8 to 250 mu g/g range, depending on the different compounds and with ESI-MS in the 3.3-8.9 to 250 ng/g range. Good determination coefficients (r(2) >= 0.99) were found in both UV-DAD and ESI-MS. Limits of quantifications ranged between 2.5 and 7.8 mu g/g for HPLC-UV-DAD assay and between 3.3 and 8.9 ng/g for HPLC-ESI-MS assay depending on different analyzed substances. At three concentrations spanning the linear dynamic ranges of both UV-DAD and ESI-MS assay, mean recoveries were always higher than 90% for the different analytes and intra-assay and inter-assay precision always better than 15% and 12%. This method was successfully applied to the analysis of substances under investigations present in cosmetic creams, freely sold on the Internet web-sites. (C) 2009 Elsevier B.V. All rights reserved.