In TXRF analysis an important consideration is the capability of the
instrument to detectwhether an element is present or not in a specimen
and to be able to show with some defined statistical certainty that a
given element is present if its concentration is greater than a lower
limit of detection (LLD) (Rousseau, 2001). The LLD, which in this
study is assumed to be the concentration equivalent to three standard
counting errors of a set of measurements of the background intensity
(Bruker, 2007), was calculated using the following formula