Smoking fingers

A team of scientists has conducted an experiment using capillary-scale ion chromatography with suppressed conductivity detection to analyse gunshot residues, sweat and latent human fingerprints.1

They tested particle-packed and polymer monolith capillary ion exchange resins for their chromatographic efficiencies, operating back pressures and thermal selectivities. The team separated a selection of inorganic and organic anions in under 23 minutes using an injection volume of 0.4 µL using a multistep hydroxide gradient. Linearity, range, reproducibility and sensitivity were tested to define method performance and then compared to a microbore (2 mm) IC method. Limits of mass sensitivity improved by factors up to 1800-fold using the capillary IC system and lay in the range of 0.3–26.2 pg. The final method was then applied to determine the presence of both endogenous and exogenous species in sweat and fingermark deposits.

The team were able to demonstrate that the method was sensitive enough to determine the difference between the sweat of three moderate (5–10 cigarettes a day) smokers in comparison to non-smokers. Smokers had elevated levels of thiocyanate and benzoate in their sweat compared with non-smokers. The team also conducted a controlled firing experiment to assess the transfer of gunshot residue onto the fingerprints of a firer. They were also able to show that direct contact with a black powder substitute (Pyrodex) could be identified by analysis of latent fingerprints.

The experiment is believed to be the first of its kind using capillary-scale suppressed ion chromatography to study sweat and fingerprints.

1. Leon Barron et al., Analyst, DOI: 10.1039/C2AN16126E (2012).

This story originally appeared in The Column. Click here to view that issue.