A scintillator-fiber flow-cell radioactivity detector for liquid chromatography

A new type of heterogeneous flow-cell radioactivity detector has been designed and developed which is packed with aligned scintillator-fibers instead of the solid scintillator particles currently used in heterogeneous flow cells. The present fiber-scintillator flow-cell radioactivity detector was designed to overcome the light scattering difficulties of the conventional heterogeneous type detector. Improved back pressure and sample retention characteristics were also expected due to the alignment of the fibers. The fiber-scintillator detector has shown good detection efficiency for most beta emitting isotopes when 0.1-mm diameter fibers were used. The fiber-cell has also demonstrated improved compound retention characteristics and a back pressure which is more than a factor of 50 less than that of typical commercially available particle-scintillator cells. The experimental detection efficiency observed with the fiber cell was, in most cases, very close to the theoretical geometric efficiency predicted by a computer model which was also developed. It is concluded that the most significant factor which limits the efficiency for most beta emitters is cell geometry. Further improvements in fiber cell efficiency would require the use of smaller and/or more uniform diameter fibers. However, for very low energy beta emitters such as tritium, it appears that the low pulse height available for detection may be the primary limiting factor