Sequential Determination of a Combined γ/β and Pure β-Emitter by Gamma and Liquid Scintillation Counting: Application to the Transport of Metals across Fish Gills

• Published in: Analytical biochemistry 1995, Vol.224 (1), p.92-99
• Main Authors: Vanginneken, L., Blust, R.
• Format: Article
• Language: English
• Subjects: Animals; Biological Transport; Calcium Radioisotopes - pharmacokinetics; Carps - metabolism; Cobalt Radioisotopes - pharmacokinetics; Gills - metabolism; Scintillation Counting
• ISSN: 0003-2697; 1096-0309
• DOI: 10.1006/abio.1995.1012

A combined gamma scintillation/liquid scintillation technique for the sequential determination of two radioactive tracers is described. The method was developed using a combined γ/β-emitter ( 57Co) and a pure β-emitter ( 45Ca). First, the 57Co radioactivity was determined by counting the samples in a gamma scintillation analyzer in the energy region 80-165 keV. Next, the samples were counted in a liquid scintillation analyzer. Only one energy region was used to count both isotopes to maximize the counting efficiencies. From the difference between quenched and unquenched β-spectra, the counting region was set from 0 to 256 keV. The counting efficiency was related to a quench-indicating parameter (tSIE) for both nuclides by fitting a rectangular hyperbola to the quench data. By subtracting the 57Co counts from the observed counts in the total window, 45Ca dpm values were obtained. It is shown that the method presented gives reliable and consistent results. The recoveries of both isotopes are independent of the quench level in a large tSIE range, although five times more radioactivity is required for 45Ca than for 57Co to obtain accurate and reproducible results. The method has been used to study mechanisms of metal transport across biological interfaces.