To pretreat, or not to pretreat, that is the question. The value of pretreatment protocols in the stable carbon and nitrogen isotope analysis of archaeobotanical cereal grains from Croatia and Serbia

Isotopic analysis of archaeological charred plant remains is a useful tool to infer past agricultural practices. However, debate continues over whether charred seeds should be untreated or pretreated before analysis, to counteract any residual contamination and retrieve the “true” isotopic signature of the seed. This paper presents a case study examining whether archaeobotanical remains from Croatia and northern Serbia should be pretreated before isotopic analysis with the aim to provide a pragmatic technique for wider application. A small subset was first examined with an ATR-FTIR and then four different protocols were examined: water rinse only, two different acid-only methods and ABA (acid–base-acid). The results were inconsistent, displaying variability in the effect each protocol had on the isotopic values. Overall, it was concluded that the slight differences between untreated and pretreated sub-samples should not impact the archaeological interpretation, removing the need for pretreatment of the remaining archaeobotanical material.