Validation of a method for the determination of 14C and 63Ni in samples of concrete

For the determination of 14C, the concrete sample was distilled in inert atmosphere and the released 14CO2 was trapped in a scintillation vial with Carbo-Sorb E. Permafluor E was added and the well mixed sample was kept in the dark for 24 h, after which the preparation was measured on a liquid scintillation spectrometer. For the determination of 63Ni the sample was ignited at 550 deg C overnight and subjected to acid leaching. Nickel was then separated by a procedure which included separation from Fe by precipitation with NH4OH and precipitation of Ni with dimethylglyoxime and purification by extraction chromatography on Ni Resin; 63Ni was determined by liquid scintillation spectrophotometry of the beta radiation. The participation in the interlaboratory comparison exercise gave evidence of the reliability and quality of the results achieved by the laboratory. (P.A.)