Rapid Determination of Technetium-99 in Large Volume Seawater Samples Using Sequential Injection Extraction Chromatographic Separation and ICP-MS Measurement

摘要

An automated method was developed for rapid determination of ~(99)Tc in large volume seawater samples. The analytical procedure involves preconcentration of technetium with coprecipitation, online separation using extraction chromatography (two TEVA columns) implemented in a sequential injection setup, and measurement of ~(99)Tc by inductively coupled plasma mass spectrometry (ICP-MS). Chromatographic behaviors of technetium, molybdenum, and ruthenium were investigated, and the mechanism of adsorption and elution of TcO_(4)~(-) on a TEVA column using HNO_(3) was explored. The results show that not only NO_(3)~(-) but also acidity (or concentration of H~(+)) of the loading or eluting solution affect the adsorption and desorption of TcO_(4)~(-) on TEVA resin. Decontamination factors of more than 1 X 10~(6) for ruthenium and 5 X 10~(5) for molybdenum are achieved. Chemical yields of technetium in the overall procedure range from 60percent to 75percent depending on the sample volumes, and a detection limit of 7.5 mBq/m~(3) (or 11.5 pg/m~(3)) for 200 L of seawater was obtained. Compared with the conventional analytical procedure, the developed method significantly reduces analytical time. A batch of samples (n > 4) can be analyzed within 24 h. The method has been successfully applied for rapid and automated determination of low level ~(99)Tc in large volume seawater samples. The analytical results of seawater samples collected in Denmark show a good agreement with the values obtained using the conventional method.