Comparison of powdered enamel sample pretreatment methods for strontium isotope analysis

Most researchers assume minimal impact of pretreatment on strontium isotope ratios ( 87 Sr/ 86 Sr) for bones and teeth, methods vary tremendously. We compared 14 methods, including no prep other than powdering enamel, ashing, soaking in water, an oxidizing agent (bleach or hydrogen peroxide) acetic acid (0.1 M, 1.0 M buffered with calcium acetate), a combination these steps. prepared analyzed aliquots powdered molar enamel from three proboscideans (one modern captive Indian elephant, Elephas maximus indicus ; one Pleistocene mastodon, Mammut americanum Miocene gomphothere, Afrochoerodon kisumuensis ). Each was performed triplicate we measured Sr, Sr concentration, uranium (U) using the same lab space instrumentation all samples. Variability U concentrations considerable across pretreatments. Mean ranged 0.70999 to 0.71029 tooth, 0.71458 0.71502 0.70804 0.70817 tooth. The tooth contained least negligible U. slightly more measurable amounts U, had approximately 5x For variance concentrations, among replicates statistically indistinguishable pretreatments, but there were apparent differences pretreatments teeth. Both relatively little it is possible that small exogenous reagents, building materials dust affected some median varied considerably (but insignificantly) variability also considerable; distinct obvious patterns methods. much smaller, significant yielded comparable to, lower than, untreated powder, suggesting selective removal material high Sr. Further evaluation mechanisms driving isotopic both within warranted. Researchers should clearly report their avoid combining data obtained different Small could interpretations, especially areas where low.