VIII - Some common inorganic and organic sample preparation methods used in archaeology

Summary

This appendix describes briefly the dissolution procedures for some of the more common inorganic sample types. The use of an internal standard is discussed in Section 13.3.

Acidification for the preparation of water samples

Water samples are amongst the simplest to prepare, simply requiring acidification to keep the sample elements in solution and to matrix-match with the calibration solutions, and the addition of an internal standard. The procedure is as follows.

• Centrifugation or filtration to remove suspended particles

• Add 2 ml of super purity acid (SPA) (or equivalent) nitric acid

• Add internal standard

• Make up to 100 ml in volumetric flask.

Open vessel digestion (HNO₃) for bones, teeth, hair, and soil

This is a standard preparation for most organic samples. In the case of soils, nitric acid will not fully dissolve all of the sample, but this method is sufficient to examine the total “available” elements.

• Accurately weigh c. 0.1g of finely powdered sample in Teflon beaker

• Add 2 ml of SPA nitric acid

• Heat gently until digested

• Allow to cool

• Add internal standard

• Make up to 100 ml in volumetric flask.

Open vessel digestion (HF:HClO₄) for ceramics, glass, rocks, and soil

These acids should completely dissolve most materials. HF removes the silica (as volatile SiF₄), which reduces the total dissolved solid content and therefore reduces interferences, and ClO₄⁻ produces perchlorates, which are soluble (but explosive if dried out). The use of hydrofluoric and perchloric acids therefore has considerable safety risks and requires specialized fume hoods, handling equipment, and safety equipment.