DETECTION LIMIT
The lowest concentration that can reliably be detected above the level of the background. To achieve low (10-100 ppm) detection level requires a large number of counts which means running at maximum currents (hundreds of nA), long times (100s of seconds) and the highest accelerating voltage possible. It has been shown that (P2/B) is the "figure of merit" for trace element analysis, and it increases for many elements with increasing accelerating voltage.
Probe for EPMA offers two versions of the detection limit calculation. The first is for each line ("single line") which means that in a heterogeneous material, it is the detection limit for each measured spot. Alternatively, if many counts are acquired on a homogeneous material, then they can be averaged, yielding a lower detection limit. The software provides such a detection limit for an average sample at a variety of confidence levels (normal level is 99%) utilizing a T-test. (see T-test)