New way eases gunshot forensics (Science Alert)

New way eases gunshot forensics (Science Alert)

"Forensic detection of gunshot residues at crime scenes could be made easier and more affordable with further development of detecting barium (Ba) through anodic stripping voltammetry.

ECU School of Natural Sciences researcher Dr Magdalena Warjak says that while lead (Pb), antimony (Sb), and copper (Cu) in gunshot residues could be detected, barium is more difficult.

“There is no reliable and highly accurate on-site method for barium detection and many other industries, such as oil and gas, use barium compounds and need to constantly monitor barium concentrations in their waste before releasing it into the environment,” she says.

“Anodic stripping voltammetry is an analytical technique that allows us to detect very low levels of metal and semi-metal ions present in liquid samples, using oxidation and reduction processes—concentrations down to micrograms per litre (µg) or parts per billion (ppb).

“Each metal or semi-metal has a different stripping potential and that’s how we can identify what metals are present in a particular sample.

“The main problem is barium requires very negative potential values for the barium ions to be deposited on the working electrode and this consequently causes problems with sensitivity, reproducibility and accuracy with its detection.

“The research involves investigating different electrolyte solutions, a variety of working electrodes and the use of an ultrasonic probe to reduce interference from gases formation.”

Using a portable digital voltammeter (PDV6000+), Dr Warjak has been able to detect barium in 10ppb and 20ppb barium standard solutions—the next goal is to lower the detection limit and then test the method on real gunshot residue samples.

“Currently, gunshot residues are collected using special adhesive sampling discs of various surfaces around crime scenes which must then be sent to be analysed qualitatively by a scanning electron microscope,” she says.

“This process is expensive, takes considerable time, requires trained chemists and may require additional samples to be collected later.

“It would be useful in some cases to perform a screen test to determine the presence of barium, lead and antimony in samples before sending them to the laboratory.”

Interest in Dr Warjak’s work has already come from the UK’s Cogent Environmental Company because it has clients that need to detect barium in industrial wastewater on-site.

“Anodic stripping voltammetry has yet to be presented to police forensic departments until the method has been developed and tested on real gunshot residue samples,” she says.

Dr Warjak expects her research on the residues to be finished by the end of the year."