The determination of tungsten in biological material by activation analysis.

Tungsten exists at such low concentrations in normal biological material that it has been detected only in tissues from animals previously fed with unusually large quantities of tungsten (Kinard & Van de Erve, 1941), or plants growing in tungsten-rich soils (J. P. R. Polkinhorne, personal communication). In view of the discovery that the related element molybdenum is essential for plants and animals and is a constituent of at least two enzyme systems, it would seem that further measurements of tungsten might yield equally interesting results. The present note describes a technique capable of detecting as little as 1 itmg. of tungsten. The method used is that of activation analysis, which is now established as an extremely sensitive technique for determining trace elements in tissue (Loveridge & Smales, 1957; Bowen & Cawse, 1959). A number of workers have studied the distribution of tungsten in samples of geochemical and metallurgical interest by this technique (e.g. Atkins & Smales, 1959; Leliart, Hoste & Eeckhaut, 1959), and a recent paper describes the determination of the element in various marine organisms (Fukai & Meinke, 1959). Tungsten has a relatively high cross-section for thermal neutrons (much higher than that of molybdenum) and, among the radioactive isotopes produced, 24-hr. '57W is much the most abundant. In this work chemical methods were used to isolate the 187W activity from the other radioelements occurring in the activated material. Contamination before activation was minimized as described in the next section, and subsequent contamination would not affect the analysis.