Analysis of high-purity water: a direct determination of ultratrace inorganic impurities by monostandard neutron activation analysis

A direct method for determining ultratrace inorganic impurities in high-purity water is presented, which consists in activation of a large volume of water (250 ml) by reactor neutron activation, subsequent gamma spectrometric assay and concentration evaluation by the monostandard procedure. The method requires neither preconcentration nor postconcentration and provides a sensitivity for a large number of elements in the concentration range of parts per trillion (ppt: 10^-12 g/g) or even much less. Using the method, over twenty different ultratrace elements are quantitatively determined in two different high-purity waters, i.e., bidistilled water and water from a Super-Q system. Problems involved in analysing such highpurity waters are discussed.