BGS stable isotope laboratories, we designed an experiment to test this using a range of cleaning methods. For isotopic work, cleaning was performed using chemical oxidation, vacuum roasting and plasma ashing; for trace element work we used sonication, chemical oxidation and reductive cleaning. These methods were compared to simple ‘manual’ cleaning using a paint brush to remove visible material. Cleaning methods were compared by undertaking analyses on a single ostracod carapace (two separate ‘valves’, similar to a mussel, which together form the ‘shell’); in modern ostracods, the two valves should have identical trace element and isotope ratios. One valve was cleaned using one of the methods above, and the other was manually cleaned using a paintbrush. Any difference between the two valves after cleaning could be assigned to the effect of the treatment method.
For more information on the study and the recommended methods, the open access paper is reference is: Roberts, L.R., Holmes, J.A., Leng, M.J., Sloane, H.J., Horne, D.J. Effects of cleaning methods upon preservation of stable isotopes and trace elements in ostracod shells: Implications for palaeoenvironmental reconstruction. Quaternary Science Reviews, 189, 197-209. The paper can be download for free here.