Effect of Temperature on the Diffusivity of Fatty Acids for Age Dating of Fingerprints using Time-of-Flight Secondary Ion Mass Spectrometry

Published

September 13, 2017

Author(s)

Shinichiro N. Muramoto, Sarah E. Smith

Abstract

In the previous work, palmitic acid in sebum was used as a chronological marker for age dating of fingerprints, using time-of-flight secondary ion mass spectrometry (ToF-SIMS) to visualize its spreading on the surface. Its diffusivity assuming an infinite-source model was determined to be (4.5 ± 0.3) × 10-4 mm2/h on a clean silicon wafer held at room temperature. In this work, the feasibility of age determination is tested for the same system up to 13 days. It was found that while palmitic acid molecules follow the infinite-source model up until t = 72 h, older samples exhibited a limited-source condition where the total number of molecules available for diffusion was conserved, leading to a decrease in diffusivity with time that limited age dating to roughly 12 days for fingerprints on a silicon wafer. In addition, exposure of the fingerprints to temperatures of (-7, 7, 21, 28, and 35) °C revealed an Arrhenius dependence on the diffusion rate with an activation energy of (21.5 ± 2.4) KJ/mol, showing that the position of palmitic acid could still be determined irrespective of aging time and temperature.

Citation

Analyst

Pub Type

Journals

Keywords

tof-sims, chemical imaging, fingerprints, sebum, forensics, diffusion

Citation

Muramoto, S. and Smith, S. (2017), Effect of Temperature on the Diffusivity of Fatty Acids for Age Dating of Fingerprints using Time-of-Flight Secondary Ion Mass Spectrometry, Analyst (Accessed April 25, 2024)