A precaution in the application of the coincidence method for determining 125I decay rates

The X-ray/X-ray coincidence method is an accurate and simple technique for calculating absolute disintegration rates for any 125I source. The calculation of dpm (disintegrations per minute) compensates for some of the variations in 125I counting efficiency caused by changes in sample volume, sample composition, container material and geometry. In the practical application of this technique there are some potential sources of error. These errors result in low dpm values and become more significant with increasing volume, increasing solute molarities, and increasing absorptivity of solutes. (author)