Methodology

Sample Materials

Most stable isotope ratio analysis in archaeology uses bone/tooth tissues from recovered human and animal remains. Other biological materials such as hair, nail, and muscle tissue may also be used if preservation is extraordinary. Residuals, such as encrustations on pottery, may also be analyzed using isotopic methods.

Good bone preservation is paramount to producing good results, particularly with regard to retrieving its protein component, bone collagen. Bone apatite, its mineral component, also provides a biological signal and can be retrieved. Ideally, bone samples should have good cortical integrity and have not been applied with any preservative. Tooth enamel is used in palaeontological and palaeoecological applications, and increasingly in archaeology. Tooth enamel is less prone to diagenesis than bone, although rather than representing average diet over a period of years (as is represented by bone), ‘bulk’ analysis represents dietary intake during the time of crown formation (e. g., 2-3 years, for human molars). Advances in securing small samples at precise locations of dental tissues represents a means of coupling life history data with diet and ecology, reflecting dietary and environmental changes at weekly or monthly intervals.

Preparation and Instrumentation

Methods for preparing bone and enamel samples for isotopic analysis are well established. Bone/tooth apatite is first physically cleaned and ground to a powder. The sample is then chemically cleaned in dilute bleach or hydrogen peroxide to remove organics. To remove secondary carbonates dilute acetic acid is used and then rinsed to neutral. For insoluble bone collagen, the sample is physically cleaned and demineralized in dilute acid (e. g., HCl), rinsed to neutral pH, and then freeze-dried for analysis.