Recovery of very low level 210Po (10-12-10-14Ci) from given solutions were investigated by electrochemical displacement method, which is the simplest and has high recovery for very low level 210Po. Under experimental conditions used here, it was found that recovery even for very low level 210Po of 10-12-10-14Ci was more than 90%.
In the measurement of automotive engine oil consumption rate by the radiometric method using 35S, continuous measurement was made possible with the development of high-sensitive plastic scintillation counter which employs plastic scintillator beads. The method which burns out remaining liquid oil in a exhaust manifold with town gas burners, made the radiometric method applicable to the measurement during engine break, which had been considered to be difficult with this method. Thus, a reliable method was developed which can make rapid and continuous measurement of engine oil consumption rate through all phases of engine operating condition.
Phadebas insulin test, the Pharmacia's new insulin assay kit, was evaluated. The test is based on solid phase radioimmunoassay, in which insulin antibody is coupled by covalent linkage to Sephadex particles. Standard curves we obtained were satisfactory in sensitivity, range which they covered and reproducibility. When the same plasma samples were measured both by two antibody method and Phadebas insulin test, these gave very similar insulin levels, with the coefficient of correlation of 0.99. In solid phase radioimmunoassay, the per cent bound at the zero level (Bo/T) is generally low, and the counting error tends to be greater for higher insulin levels due to low count rate. According to our results, the mean coefficient of variation of duplicated samples was 13.4% when the radioactivity was counted for 1 minute. Counting for longer period is recommended in this method. Repeated centrifugations and washings of the precipitate are required in this method to separate bound from free insulin, because Sephadex particles are not packed tightly to the bottom of tubes. In order to simplify this separation procedure, a modification was introduced in which an aliquot of the supernatant was aspirated and counted after a single centrifugation. Standard curve obtained by this modification was almost identical to that by the standard method. It suggests that the modified method is an acceptable alternative. We further studied on the effect of incubation period in this method. Although standard curve obtained by 3 hours incubation was comparable to that obtained by overnight incubation, the coefficient of variance was greater in the former. Therefore, the standard overnight incubation is recommended to obtain valid results.