Date of Award

Summer 8-2023

Document Type


Degree Name

Master of Science (MS)


Forensic Science



First Advisor or Mentor

Ana Pego

Second Reader

Marta Concheiro-Guisan

Third Advisor

Emanuele Alves


Hair is a biological sample used in forensic toxicology to identify and quantify drug exposure. However, when interpreting analytical results, hair can be challenging due to the presence of external contamination. Previous studies have shown that cosmetic treatments remove drugs within the hair shaft decreasing their concentration. Nevertheless, not enough information is available to explain this phenomenon. This study focused to determine whether cosmetic products such as dry shampoo and gel influence the concentration of externally deposited cocaine (COC) and benzoylecgonine (BE) in different hair types/colors. Hair samples from fifteen COC-free volunteers of various hair colors/types were collected and divided into three different groups. Each group received a treatment of dry shampoo and gel. In Group A, hair samples were first treated with a cosmetic product then contaminated; in Group B, hair samples were first contaminated then treated with a cosmetic product; in Group C, hair samples only suffered contamination. The contamination procedure consisted in immersing hair samples in a 1 µg/mL COC and BE mixed solution in water for 24 h. Prior to analysis, hair samples were washed, extracted, and filtered. Dry shampoo samples resulted in a harsher removal of COC in both hair samples treated before and after, causing an average decrease in concentration of 97% and 67%, respectively. Gel treated hair samples showed an average decreased of 34% and 10%, respectively. Overall, these results suggest that cosmetic treatments do influence drug concentrations by removing COC and BE as well as preventing further COC and BE contamination.

Included in

Toxicology Commons


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