In this paper the technique and procedure were developed to determine the chemical compositions of suspended mineral particles in the different fractions of river samples by gravimetry, aqua rega-HF-H₃BO₃ digestion and ICP-AES analysis. Particulate Si, Al, Ca, Fe, Mg and Mn in the different fractions can be determined simutaneously, precisely and accurately with a simple procedure at very low concentrations. The loss of Si in the digestion was not observed. The presence of boric acid did not cause any interference in the analysis. The comparisons between digested and non-digested particles in the fractions of diameters < 3μm, <2–3 μm and >0.8 μm were made. A negative error occurred in non digested particles.