Effects of lipid extraction and ultrafiltration on stable carbon and nitrogen isotopic compositions of fish bone collagen

Abstract

The chemical lipid extraction method (2:1 chloroform/methanol) performed significantly better than the physical lipid extraction method (30 kDa ultrafilters). Given the high quantities of lipids in fish bones we recommend the inclusion of a chemical lipid extraction step when isolating collagen from modern and archaeological fish bones. Copyright © 2016 John Wiley & Sons, Ltd.

Lake Ontario salmon (Salmo salar) were not migratory: A long-standing historical debate solved through stable isotope analysis

“…In contrast, δ 13 C, δ 15 N, and δ 34 S analyses of fish bone collagen have well-established criteria for assessing sample integrity in archaeological contexts where diagenesis may be a problem42434445 and are also well suited for reconstructing ecosystem nutrient relationships464748 as well as identifying marine and freshwater migratory behaviour32333435.…”

“…Samples were then treated three times with 2:1 chloroform-methanol in an ultrasonic bath (5–10 min each) to remove residual lipids4257. Sample demineralization was then achieved by soaking samples in 0.5 M HCl.…”

“…Samples were then rinsed in Type I water to neutrality, and base-soluble contaminants were removed by treating samples with 0.1 M NaOH several times in an ultrasonic bath (solution refreshed every 15 min until solution remained clear). Samples were again rinsed in Type I water to neutrality and then solubilized in 10 −3 M HCl (pH ~3) in a heating block (at 75 °C) for 48 h. The solution was then purified using 45–90 μm mesh filters to remove particulates (Elkay Laboratory Products, Basingstoke, UK) and 10 kDa MWCO filters (Pall Corporation, Port Washington, NY, USA) to remove low molecular weight contaminants4258. The solution containing the >10 kDa fraction was frozen and lyophilized.…”

Effects of skeletal element identity, delipidation and demineralization on the analysis of stable isotope ratios of C and N in fish bone

“…obs. ), although this could be improved using an ultrasonic bath (Guiry et al ., ). Furthermore, recently Guiry et al .…”

“…Both carbonate and lipids may bias δ 13 C values in opposite ways (Szpak, ; Guiry et al ., ). Although bone samples are usually demineralized with hydrochloric acid (HCl) and lipids are removed with organic solvents (Pinnegar & Polunin, ; Newsome et al ., ; Szpak, ; Guiry et al ., ), delipidation is not standard practice in archaeology (Guiry et al ., ). Collagen is the main protein in bone and is highly stable at low pH at ambient temperature (Brown et al ., ; Gage et al ., ).…”