Standard method of test for radioactive manganese in water

A method is described for the determination of concentrations of 54Mn and 56Mn above 10-3 μCi/l in H2O. Radioactive Mn and carrier are first precipitated as MnO2 and finally as the gravimetric precipitate Mn(H2PO4)2 for chemical yield determination and counting. The final precipitate is mounted and counted by γ spectrometry using a Ge(Li) or NaI detector. Using a Ge(Li) detector, the peaks of the two isotopes are separated, and only a single measurement is required; however, if a NaI detector is used and both isotopes are to be determined, two countings are necessary. The first is made immediately after the chemical separation, and the second is made about 2 days later after the 56Mn has decayed leaving a direct measure of the 54Mn. The 56Mn is then determined by difference. A large amount of chloride makes the first precipitation difficult, and large amounts of stable Mn will cause errors in the chemical yield determination. The standard deviation of the method for a single operator is 2.5 percent