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Introduction -- Sunscreen Cosmetics: Advantages and Drawbacks -- Development of a Chromatographic Method to Estimate the In Vitro Percutaneous Absorption of Hydrosoluble UV Filters -- Determination of the Unconjugated Forms of Benzophenone-3 and Benzophenone-4 in Urine by Solid-Phase Extraction Coupled to a Liquid Chromatographic System with UV/VIS Detection by Using Autormated Sequential Injection Analysis -- Determination of Benzophenone-3 and Their Metabolites in Urine by Solid-Phase Extraction and Liquid Chromatography Tandem Mass Spectrometry -- Determination of Benzophenone-3 and Its Metabolites in Human Semen by Solid-Phase Extraction and Liquid Chromatography Tandem Mass Spectroscopy -- Eluciation of the In Vitro Biotransformation Products of Ethylhexyl Dimthyl PABA by Chromatographic Techniques Coupled to Mass Spectrometry -- Elucidation of the In Vivo Biotransformation Products of Ethylhexyl Dimethyl PABA By Liquid Chromatographic Techniques with Mass Spectrometry Detectors -- Determination of Ethylhexl Dimethyl PABA and Its Metabolites in Semen by Automated Solid-Phase Extraction and Liquid Chromatography Tandem Mass Spectrometry -- Determination of Methyl Benzylidene Camphor and Its Main Metabolite in Urine by Solid-Phase Extraction and Liquid Chromatography Tandem Mass Spectrometry -- Summary and General Conclusions.

Zacarías León's thesis describes the development and validation of analytical methods to estimate the processes set in motion by percutaneous absorption of UV filters in sunscreen cosmetic products. León describes these methods in both in vitro and non-invasive in vivo methodologies. Currently dermatologists recommend the use of sunscreen products not only under conditions of extreme exposure to the sun but also in daily situations. However the chemical compounds in these products contain may lead to undesired processes and cause induced toxicity, estogenic effects and endocrine activity. León establishes methods to investigate these effects and provides valuable information on the undesired side effects associated with the use of UV filters found in sunscreen products. The work in this thesis has led to a number of publications in renowned analytical chemistry journals.