Simple liquid-liquid extraction of U and Th in tracer amounts from phosphate matrix for dating purposes

Existing procedures for 230Th dating of phosphate-rich materials (bone, teeth) are labor-intensive and troubled with variable, operator-dependent results. A liquid-liquid extraction procedure was developed, using a long-chained quaternary ammonium salt as the organic extractor. Quantitative separation of U and Th with chemical yields of 80–90% are attainable, at a tolerance of up to 200 g Ca3(PO4)2 per litre dissolved sample. Liquid-liquid extraction is very fast, and appears not to produce any bias on the resulting dates, as compared with the more time-consuming ion-exchange chromatographic methods in common use. The technique also works well on conventional material, like carbonate fossils and speleothems.