Automatic and Simple Method for 99Tc Determination Using a Selective Resin and Liquid Scintillation Detection Applied to Urine Samples

99mTc (6.0067 h half-life) is an artificial radionuclide largely used in diagnostic medicine. Its daughter 99Tc is a beta emitter of great concern because of its long half-life (2.111 × 105 years) and presumed mobile behavior in the environment. To monitor the 99Tc in urine from treated patients, an automatic Lab-on-valve (LOV) system for separation and preconcentration of 99Tc was developed. TEVA resin was selected since it retains pertechnetate ion selectively from diluted nitric acid solutions. After elution, 99Tc is detected using a liquid scintillation counting (LSC) detector. The present method has been successfully applied to urine samples with low 99Tc content (recoveries between 94–111%). The minimum detectable activity (MDA) of the developed method is 0.1 Bq or 1 Bq L–1 (expressed as activity concentration), when preconcentrating 100 mL of sample. The high durability of the resin, together with the low amount of resin required (32 mg), the good reproducibility (RSD 2%, n = 5) and the high extraction frequency (up to 12 h–1) makes of the present method an inexpensive, precise and fast useful tool for monitoring 99Tc in urine samples.