Analysis of Handwashings for Gunshot Residue
To identify gunshot residue, if any, by the presence of lead on the hands.
Have someone fire a handgun at a firing range. Immediately swab each hand with a cotton swab wetted with 0.8 M nitric acid. Swab the thumb web, palm, and back of the hand. Place each swab in a separate plastic bag and seal. Repeat the process for someone who only handled the gun after it was fired.
Alternatively, prepare simulated hand-swabbings by adding lead nitrate solution to cotton swabs wetted with 0.8 M nitric acid. The added lead standard should contain 50 - 100 µg of lead (fired a gun) or 25-50 µg of lead (handled a gun).
1000 ppm lead solution (as lead nitrate) in 1% (v/v) nitric acid; nitric acid; ammonium dihydrogen phosphate (ultrapure; matrix modifier)
Standard Reference Material
500 ppb lead solution (as lead nitrate) in 1% (v/v) nitric acid
Electrothermal atomic absorption spectrophotometry
Atomic absorption spectrophotometer with graphite furnace atomizer
Atomic absorption calibration curve for lead
Scanning electron microscopy / X-ray fluorescence (SEM-EDX)
(planned for next edition)