title: Confocal Raman spectroscopy to trace lipstick with their smudges on different surfaces.
abstract: Lipsticks are very popular cosmetic products that can be transferred by contact to different surfaces, being important forensic evidence with an intricate analysis if they are found in a crime scene. This study evaluates the use of confocal Raman microscopy at 780 nm excitation wavelength for the nondestructive identification of 49 lipsticks of different brands and colors, overcoming the lipstick fluorescence problem reported by previous works using other laser wavelengths. Although the lipsticks samples showed some fluorescence, this effect was not so intense to completely overwhelm the Raman spectra. Lipsticks smudges on twelve different surfaces commonly stained with these samples were also analyzed. In the case of the surfaces, some of them provided several bands to the smudge spectra compromising the identification of the lipstick. For these samples spectral subtraction of the interfering bands from the surface was performed. Finally, five different red lipsticks with very similar color were measured on different surfaces to evaluate the lipstick traceability with their smudges even on interfering surfaces. Although previous spectral subtraction was needed in some cases, all the smudged were linked to their corresponding lipsticks even when they are smeared on the interfering surfaces. As a consequence, confocal Raman microscopy using the 780 nm excitation laser is presented as a nondestructive powerful tool for the identification of these tricky samples.
authors.affiliation: University Institute of Research in Police Sciences, University of Alcalá, Ctra. Madrid-Barcelona Km. 33.600, 28871 Alcalá de Henares (Madrid), Spain; Department of Analytical Chemistry, Physical Chemistry and Chemical Engineering, Multipurpose Building of Chemistry, University of Alcalá, Ctra. Madrid-Barcelona Km. 33.600, 28871 Alcalá de Henares (Madrid), Spain.
authors.forename: Maria
authors.initials: M
authors.lastname: López-López
authors.affiliation: Department of Chemistry, Faculty of Arts & Science, Istanbul Technical University, 34469 Maslak, Istanbul, Turkey.
authors.forename: Nil
authors.initials: N
authors.lastname: Özbek
authors.affiliation: University Institute of Research in Police Sciences, University of Alcalá, Ctra. Madrid-Barcelona Km. 33.600, 28871 Alcalá de Henares (Madrid), Spain; Department of Analytical Chemistry, Physical Chemistry and Chemical Engineering, Multipurpose Building of Chemistry, University of Alcalá, Ctra. Madrid-Barcelona Km. 33.600, 28871 Alcalá de Henares (Madrid), Spain. Electronic address: carmen.gruiz@uah.es.
authors.forename: Carmen
authors.initials: C
authors.lastname: García-Ruiz
mesh_terms: D003116:Color; D003358:Cosmetics / Q000032:analysis* / Q000737:chemistry; D005453:Fluorescence; D044707:Forensic Sciences / Q000379:methods; D006801:Humans; D015203:Reproducibility of Results; D013059:Spectrum Analysis, Raman / Q000379:methods*; D013499:Surface Properties; D013997:Time Factors
chemical_list: D003358:Cosmetics
keywords: Lipstick; Raman spectroscopy; lipstick smudges