An optical emission spectrometry with the ionization in inductively coupled plasma was tested as a potential anal. method for detn. of trace amts. of Cd, Pb, Ni and Cr in phosphorites -based materials, which were previously shredded and dissolved in a mixt. of concd. HNO3 and HCl acids in the ratio of 3:1 by vol. The markings were carried out without correction of the calibration as well as using Sc, Be and Cs solns. as internal stds. The calibration resulted in an increase in the accuracy of markings of the tested elements in the certified ref. material by approx. 10%.