A live-timed bi-dimensional data acquisition system was applied for standardization of152Eu by 4 πβ-γ spectroscopic coincidence counting that was proposed by Baba et al. [Nucl. Instr. Meth., 203, 273 (1982) ] . A 4 πβ pressurized proportional counter detects β-particles, Auger electrons and X-rays, and a high purity germanium detector measures γ rays. Digitized data from both detectors on coincidences and anti-coincidences are stored on magnetic tapes. A micro computer extracts the single γ spectrum and the γ spectrum coincident with the β pulses from them, and activity of152Eu is calculated from both spectra by the 4 πβ-γ spec-troscopic coincidence method. This apparatus not only decrease a half of measurement time but also the statistical uncertainty is largely improved. Furthermore, it is effective that the detection efficiencies unknown for β-rays are estimated using mass absorption coefficients.
Absorption, distribution, metabolism and excretion were studied in rats following a single oral administration of N-cyclohexyl-2-benzothiazyl sulfenamide (CBS) at a dose of 250 mg/kg. About 65% and 24% of the dose were excreted into urine and feces, respectively, for 3 days after administration of labeled CBS (cyclohexyl-14C) Biliary excretion amounted to about 5 % of the dose for 3 days. While about 92% of the dose was recovered in urine and feces at a ratio of 1: 1 within 3 days when14C-2CBS was given. No specific organ-affinity was observed in distribution study. Cyclohexylamine and 2-mer-captobenzothiazole were identified as urinary metabolites.
We tested the performance of “Ready Cap” which can be used in place of liquid scintillation cocktails to measure the activity of3H and14C with a liquid scintillation counter, and observed satisfactory results on counting efficiencies for these nuclides. We could correct color-quenching with Ready Cap either by a method of the gravity-center of β-ray spectrum or by an external standard method that uses the external irradiation from bottom of the sample. Although there are several problems such as limitation of the maximum sample volumes (<200 μl) and sample preparation procedures (drying the sample solution), we can conveniently employ Ready Cap in some aspects of activity counting because of the easy disposal procedure of the radioactive waste resulting from it.
We carried out the efficiency test of Ready Cap, a solvent free scintillation material, using a non-volatile3H-labeled compound and a liquid scintillation counter (Aloka LSC-1000) . The following results were obtained: (1) The tritium efficiency was about 40% and varied narrowly. (2) Potential sample volume for high efficiency was up to 200 μl. (3) Significant decrease in the counting efficiency was caused by incomplete drying and the presence of non-volatile solutes such as high molarity buffers. (4) Chemiluminescence was not observed. (5) Color quenching correction except high quenching level was successfully made by SCCR method. Thus, it is suggested that Ready Cap might be convenient for measurement of counting rate, althongh this method is limited in quantitative estimation of radioactivity.