Single shot, single sample, single instrument detection of IGSR and OGSR using LC/MS/MS

Area of Science:

• Forensic Science
• Analytical Chemistry
• Mass Spectrometry

Background:

• Firearm discharge residue (FDR) comprises organic and inorganic components from firearm components.
• Current forensic analysis often separates inorganic primer residues (IGSR) and organic residues (OGSR) using different techniques.
• Advances in mass spectrometry enable sensitive detection of both organic and inorganic residues.

Purpose of the Study:

• To develop an innovative, integrated method for simultaneous collection and analysis of both IGSR and OGSR from a single sample.
• To characterize FDR using a single analytical instrument, LC coupled with triple quadrupole mass spectrometry.
• To leverage host-guest and ligand chemistry for the detection of inorganic constituents within FDR.

Main Methods:

• Collected IGSR and OGSR on a single SEM stub.
• Employed a two-step sequential extraction process.
• Utilized liquid chromatography coupled with triple quadrupole mass spectrometry (LC/MS/MS) for characterization, exploiting metal-ligand complex precursor ions.

Main Results:

• Successfully detected lead and elemental copper (EC) down to a single shot discharge in controlled shooting studies.
• Identified barium, calcium, and iron in the residue samples.
• Demonstrated the necessity of tartaric acid for the detection of antimony using this method.

Conclusions:

• The developed sequential extraction and LC/MS/MS method offers an efficient and integrated approach for FDR analysis.
• This technique enables the simultaneous characterization of both organic and inorganic residues from a single sample.
• The method shows promise for enhancing forensic investigations by providing comprehensive FDR analysis with improved sensitivity.