Quantitative problems in using nuclear reactions and dielectric detectors for the detection of stable isotopes (6Li and10B) in biological samples

The methodology of the detection of (n, ) nuclear reactions by means of cellulose nitrate detectors is discussed with special reference to the reliability of the quantitative estimates. The discrimination of¹⁰B and⁶Li from the other isotopes is possible by using thin coloured detectors. The ratio of the number of tracks found at the level of a¹⁰B or⁵Li-enriched calibrating sample, and the number expected from theoretical calculation, i.e. the detection efficiency, P is generally below 1. P is fairly sensitive to the experimental conditions, and for precise quantitative measurements it must be determined separately for each different experiment. The gelatin, used for solidification of liquid samples is boron contaminated (almost 1 mol natural B per g). It has been observed, especially with¹⁰B-enriched liquid samples, that part of the stable tracer under study is lost during sample preparation.⁶Li extra tracks appear at the rear face of thick, non-plastic-supported detectors. Boron diffuses in the cellulose-nitrate detectors with the diffusion coefficient of the order of 10^–8 cm²·s^–1. Therefore it requires rapid operations for microlocation of boron with high resolving power.