Extraction of selected elements from commercial fertilizers

Two commercial fertilizers preparation methods for ICP OES analysis of were used for two different fertilizers types: urea and NPK (mineral fertilizer containing nutrients N, P, and K), as organic and inorganic fertilizers, respectively. The aim of our research was the comparison of two methods for the preparation of samples, the determination of the contents of elements, and the comparison of obtained results with the maximum allowed concentrations. The first preparation method consists of digestion with 18.5% HCl, and the other method is the digestion with aqua regia. Regarding the extraction of some secondary nutrients and micronutrients (Ca, Mg, Fe, Mn, Cu, Zn, and B) from NPK fertilizer, better extraction was achieved using the first method for B, Ca, and Mg, while the other method was better for Fe, Mn, Cu, and Zn. On the basis of the results of the analysis, the digestion with aqua regia is suitable for almost all investigated 3d metals from both samples, except for NPK, for which the degree of the extraction is somewhat higher. Determined concentrations of some toxic elements (As, Cr, Cd, Ni, and Pb) do not cross the maximum allowable concentrations (MAC).