To determine the range of selectivity, the limit of detection, or other analytical parameters, i.e. validation of an analytical procedure. the extracts of control plants should be spiked with Tl(lll)DTPA standard as late as possible, to shorten the time of contact with the matrix. In order to give credibility to the obtained results it is necessary to confirm them by using an independent analytical method, alternative to Lc ICP Ms.