Online radionuclide detection

Both on-column and post-column detection schemes have been developed for radionuclide detection for CE. The most common type used is an on-column configuration, which yields detection limits in the 10 M range for isotopes such as P. Isotachophoretic separations of C were among the first examples of online capillary radionuclide detection, performed by Kaniansky et al. The associated instmment uses 300-p,m ID fluorinated ethylene-propylene copolymer capillary tubing, and the separation eluent flows directly into a plastic scintillator cell between two PMTs. The scintillation events are detected coincidentally between the two PMTs, such that only if both PMTs receive an input within a short time will they register the count as signal. This kind of coincidence detection ensures that nonscintillation photons that come from outside the detection cell and only hit one PMT are not counted. This system exhibits a detection limit of 16 Bq for analytes, with a detector efficiency of 13-15%. 

Long-lived radionuclides occur at extremely low concentrations, especially in environmental samples, therefore several authors have proposed matrix separation and enrichment of the analytes before analysis.21,24,26,3 39 Radiochemical methods often require very careful and time consuming separation and enrichment processes and measurement procedures of a-, (3- and -emitting radioactive species at the trace and ultratrace level using conventional radioanalytical techniques 40-43 Trace/matrix separation, which is performed offline or online in order to avoid possible isobaric interferences, matrix effects and to reduce the detection limits for the determination of long-lived radionuclides, is also advantageous before ICP-MS measurements as the most widely applied mass spectrometric technique. 

As an example of a fully automated system for radionuclide determination, there is a method based on SIA technique developed for Tc determination, including microwave assisted treatment, solid phase extraction (SPE) and online detection (Figure 8.6) [21]. 

Another example of system for radionuclides determination using online detection is an SIA system with bead injection (Figure 8.7) [20]. The use of a renewable column packing with selective... 

Online detection of radionuclides is also integrated in sensors developed for environmental monitoring. Sensors are constituted by a preconcentrating minicolumn packed with scintillating microspheres, which integrates radiochemical separation and radiometric detection steps within a... 

---