Evaluation of Flow Cell Detector Configurations Combining Simultaneous Preconcentration and Scintillation Detection for Monitoring of Pertechnetate in Aqueous Media

Abstract

Flow cell detectors were developed for simultaneous concentration and scintillation detection of technetium-99 in water. Evaluated flow cell geometries consisted of a coil and a fountain flow cell design; the latter is based on radial solution flow through a resin bed interfaced with a photomultiplier tube through a polycarbonate window. The sorptive scintillating media investigated were (1) an extractive scintillator combining a porous polystyrene resin with the extractant Aliquat-336 and fluor 2-(1-naphthyl)-5-phenyloxazole, (2) a mixed bed of organic scintillator (BC-400) and Tc-selective resin (TEVA), and (3) a mixed bed of inorganic scintillator particles (CaF2-Eu) with either TEVA resin or strong base anion-exchange resin (Dowex 1 x 8-400(Cl)). Depending on flow cell geometry and medium, the detection efficiencies for 99Tc ranged from 7.26 (BC-400/TEVA in coil geometry) to 50.20% (CaF2(Eu)/Dowex 1 x 8-400(Cl) in fountain flow cell geometry). The configuration with the highest sensitivity, CaF2(Eu)/Dowex 1 x 8-400(Cl) in coil geometry, can detect 99Tc as low as 3.78 Bq L(-1) for a 100-s count interval and a 200-mL sample, which is below the current regulatory level of 33 Bq L(-1). The issue of sensor reusability was addressed in this research, and its potential application at near neutral pH was demonstrated. The optimal sensor design was evaluated with a 99Tc-spiked synthetic groundwater matrix.

Development of polymerizable 2-(1-naphthyl)-5-phenyloxazole scintillators for ionizing radiation detection

“…Fig. 13 C NMR experimental spectra are given in ESI † (Fig. The figure confirms the successful organic synthesis of vNPO and allylNPO relative to the starting material (aNPO).…”

“…All 1 H and 13 C NMR spectra were recorded on a JEOL ECX-300 spectrometer operating at 300 MHz for 1 H NMR and 75 MHz for 13 C NMR at room temperature and in CDCl 3 solvent. The chemical shifts (d) are reported in ppm and were referenced to the residual solvent peak.…”

“…6 Although the sensors prepared with these resins exhibited favorable selectivity and detection efficiency, an approximate 7% decrease in the counting rate was reported as a result of organic fluor leaching after pumping approximately 5000 column void volumes (B1400 column volumes) of 25% (v/v) CH 3 OH/H 2 O solution. 6,13 The main objective of this work was to prepare stable and efficient extractive scintillating resins by synthesizing polymerizable forms of aNPO and incorporating them covalently into the resin structure. 7 The resin which has been prepared by this method was used effectively to measure 99 TcO 4 À in several natural freshwater samples with different chemical composition.…”

“…aNPO was applied recently in different radiometric applications; however, the extractive scintillating resins prepared with it suffered from different degrees of instability. 6,13 The main objective of this work was to prepare stable and efficient extractive scintillating resins by synthesizing polymerizable forms of aNPO and incorporating them covalently into the resin structure. The synthesis and characterization of 2-(1naphthyl)-4-vinyl-5-phenyloxazole (vNPO) and 2-(1-naphthyl)-4allyl-5-phenyloxazole (allylNPO) are described.…”

Automatic in-syringe dispersive liquid–liquid microextraction of 99Tc from biological samples and hospital residues prior to liquid scintillation counting

“…The obtained eluates are diluted up to a volume of 2 mL with 22.5 % Aliquat®336 in acetone and mixed with 8 mL of liquid scintillation cocktail, according to the LSC manufacturer's recommendations [19]. Borosilicate glass LSC vials were kept in the dark overnight and measured the following day to avoid interferences due to fluorescence and/or phosphorescence [20].…”