Looking into lipsticks

Lipstick traces of different colours and manufacturers have been analysed by dispersive Raman spectroscopy, providing a reasonable degree of discrimination. Michael Went and Fatma Salahioglu from the University of Kent studied 69 lipsticks in total after they had been smeared on glass microscope slides and described their findings in Forensic Science International.

Most of the spectra had a fluorescent baseline but 7 were too fluorescent to study. Of the remaining 62 samples, 15 gave unique spectra which allowed their discrimination. They included orange, brown, peach, pink and flesh colours. The remainder could be clasified into 7 groups, some of which were discriminated on the basis of colour or brand with others covering a range of colours and brands. The most difficult colour was red. All of the red lipsticks fell in the same group regardless of manufacturer. The peaks in the Raman spectra were attributed to oils, waxes and dyes, among other components.

The spectra of aged lipsticks showed no changes after one year of storage on a bench in the lab, which is an important property for forensic considerations.