Determination of uranium in tap water by ICP-MS

A fast and accurate procedure has been developed for the determination of u ranium at mu g L-1 level in tap and mineral water. The method is based on t he direct introduction of samples, without any chemical pre-treatment, into an inductively coupled plasma mass spectrometer (ICP-MS). Uranium was dete rmined at the mass number 238 using Rh as internal standard. The method pro vides a limit of detection of 2 ng L-1 and a good repeatability with relati ve standard deviation values (RSD) about 3% for five independent analyses o f samples containing 73 mu g L-1 of uranium. Recovery percentage values fou nd for the determination of uranium in spiked natural samples varied betwee n 91% and 106%. Results obtained are comparable with those found by radioch emical methods for natural samples and of the same order for the certified content of a reference material, thus indicating the accuracy of the ICP-MS procedure without the need of using isotope dilution. A series of mineral and tap waters from different pants of Spain and Morocco were analysed.