4.3.2. Optimum Counting Times

To use counting time most efficiently, and to minimize the uncertainties due to counting statistics, the times spend measuring peak and background should satisfy the following ratio:

If peak counts are much greater than background counts, the background measurement hardly matters; however, if peak counts are near background counts (as for trace elements), it is necessary to spend as much time establishing the background as counting on the peak. Typically, it is better to choose a standard with a high concentration of the element of interest so that is it not necessary to count its background for very long. Backgrounds should be taken on both sides of the peak when dealing with low concentrations of the element of interest. In extreme cases, it may be necessary to profile the background on a standard that contains none of the element of interest.