Serious complications in the liquid scintillation counting analysis of mercury-203

The decrease in the count rate of mercury-203 as calculated from its half-life is approximately 0.06% per hour. In actual practice using liquid scintillation counting, this decrease can be far greater. It is shown that fluorescence, adsorption, and chemical reduction followed by volatilization are not responsible for this apparent loss of activity. The origin of the phenomenon is shown to be precipitation in the short term (24 h) followed by surface adsorption of the precipate in the longer term (greater than 2 days).