RESUMO
A simple method, based on inductively coupled plasma mass spectrometry, for determination of uranium in urine at levels that indicate occupational exposure, is presented. Sample preparation involves a fifty-fold dilution of the urine by nitric acid (2% HNO3) and no other chemical treatment or separation. The analysis itself is completed in under 3 min. The analytical procedure is fully automated so that a technician may perform over 100 analyses per day. With proper control of the blank contribution, a lower limit of detection of 3 ng L(-1) in the original urine sample was achieved. Uranium concentrations in the range 6-30 ng L(-1) were found in urine samples of people that are not occupationally exposed. The validity of the results was demonstrated through measurement of standards, controlled uranium addition experiments and, at higher concentrations, by comparison with results obtained by an independent method based on laser induced fluorescence. The laser induced fluorescence technique was found to be sufficient for detection of occupational exposure at an action level of 1.5 microg L(-1). Use of internal standards, indium, and thallium, improved quantification by about 10%, but was not deemed necessary for routine analysis. The inductively coupled plasma mass spectrometry is also ideally suited for monitoring uranium in fresh water and drinking water, as no sample dilution is required and the lower limit of detection is below 0.15 ng L(-1).