Preservation of hair stable isotope signatures during freezing and law enforcement evidence packaging

The use of stable isotopes in postconflict forensic identification

“…Instead, preparation of these keratinous tissues focuses on cleaning and then, if needed, sequential sampling (Mancuso & Ehleringer, 2019b; O'Connell et al, 2001; O'Connell & Hedges, 1999). Cleaning starts with a solvent wash, typically using a mixture of chloroform and methanol (Gordon et al, 2018; Kootker et al, 2020; Mancuso & Ehleringer, 2019b; O'Connell & Hedges, 1999), and then samples are dried at room temperature. For tissues recovered from forensic settings, physical debris can be first removed using forceps and low‐lint laboratory wipes (Gordon et al, 2018); a blast of high pressure N 2 gas (Kootker et al, 2020); or a drop of mild detergent, such as dish soap, in water (Saul et al, in press).…”

“…Cleaning starts with a solvent wash, typically using a mixture of chloroform and methanol (Gordon et al, 2018; Kootker et al, 2020; Mancuso & Ehleringer, 2019b; O'Connell & Hedges, 1999), and then samples are dried at room temperature. For tissues recovered from forensic settings, physical debris can be first removed using forceps and low‐lint laboratory wipes (Gordon et al, 2018); a blast of high pressure N 2 gas (Kootker et al, 2020); or a drop of mild detergent, such as dish soap, in water (Saul et al, in press). Hair and nail prepared for measurement of hydrogen isotopes must either be equilibrated with (1) local laboratory atmosphere, as per guidance for the reference materials USGS42 and USGS43 (Coplen & Qi, 2012, 2016); (2) humidity within a sealed chamber, which can provide more consistent conditions and reproducible results; or (3) an online preparation system that can reduce equilibration time from days to hours (Soto et al, 2017; Wassenaar et al, 2015).…”