Synthesis of Precision for the Certification of Phosphorus in Biological Materials by INAA

The β-emitter32P was used to determine total phosphorus by INAA in Skim Milk Powder RM 63, a material now certified by the EEC Bureau of Reference (BCR). Samples and comparator were irradiated in the Danish reactor DR 3. One month later the samples were dissolved in water and aliquots counted with a GM end-window counter using absorber thicknesses of zero to 400 mg/cm2. The Synthesis of Precision was introduced to find the absorber best suited for discriminating against other β-emitting isotopes and at the same time giving maximum precision.