Coincidence radioisotope detector

Table III. Injection Data for Coincidence Radioisotope Detector CE System...

Figure 6. Capillary electropherogram of adenosine-5 -[7-S2P] triphosphate obtained by injecting approximately 25 nCi (6 x 10 M solution) onto the capillary and applying a constant potential of -25 kV. The separation was monitored using the coincidence radioisotope detector.

Table VI. Coincidence Radioisotope Detector Efficiency Data...

Figure 11. Capillary gel electrophoresis separation a poly (T) oligomer sample S2P-labeled at the 5 end. Detection was accomplished using the coincidence radioisotope detector.

We report here the design and characterization of three simple, on-line radioisotope detectors for capillary electrophoresis. The first detector utilizes a commercially available semiconductor device responding directly to 7 rays or particles that pass through the walls of the fused silica separation channel. A similar semiconductor detector for 7-emitting radiopharmaceuticals separated by HPLC was reported by Needham and Delaney (XI). The second detector utilizes a commercially available plastic scintillator material that completely surrounds (360 ) the detection region of the separation channel. Light emitted by the plastic scintillator is collected and focused onto the photocathode of a cooled photomultiplier tube. Alternatively, a third detection scheme utilizes a disk fashioned from commercially available plastic scintillator material positioned between two-room temperature photomultiplier tubes operated in the coincidence counting mode. 

Figure 17.3—Counting system, a) Device used to measure the activity of a low-energy radioisotope using the method of two coincident detectors. A single ft emission can produce hundreds of photons. It is thus possible to measure photons in opposite directions using two photomultiplier tubes (PMT). Counting only occurs if both PMTs produce a signal that is not offset by more than a few nanoseconds b) device involving a PMT in a counting well used to measure luminescence produced by a sample that has been mixed with a scintillation cocktail (in aqueous or non-aqueous media).

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