Stability of nonsteroidal anti-inflammatory drugs in contaminated fingermarks probed by Raman Spectroscopy: Effect of temperature and time since deposition

For over a decade, chemical analysis of fingermarks (FMs), with particular reference to “touch chemistry,” has offered additional intelligence to the forensics community. Therefore, understanding the FM degradation trends in the presence of exogenous contaminants is vital. The current study aimed to investigate the underlying changes in drugs in contaminated FMs upon exposure to different temperatures and times since deposition using Raman spectroscopy. For this purpose, five non-steroidal anti-inflammatory drugs (NSAIDs) were used to produce contaminated FMs, and their change at various temperatures and times was studied. We found that the Raman signal of aspirin, diclofenac, and ibuprofen in contaminated FMs were significantly reduced at high temperatures, whereas naproxen and ketoprofen were more stable at the studied temperatures. Furthermore, the chemical/physical changes of these drugs in FM samples were monitored for 40 days post-deposition. The Raman spectra of the FM contaminated with aspirin exhibited monotonic changes over time, whereas the diclofenac-, ibuprofen-, ketoprofen-, and naproxen-contaminated FMs showed little change. Additionally, the intensity of the Raman bands assigned to individual drugs showed a monoexponential decrease with time since FM deposition, and the characteristic decay time of each drug varied between 5 and 600 h. The present study advances the use of Raman spectroscopy to study the stability of drugs in FM samples exposed to high temperatures and aged up to 40 days.