The masses of single SiO₂ and Au nano- and microspheres were measured by introducing monodisperse droplets of diluted Au and SiO₂ particle suspensions into an ICP-OES system and calibrating the element line intensities by respective intensities obtained with monodisperse droplets of Si and Au standard solutions with known concentrations and diameters. Commercially available SiO₂ (diameters between 470 nm and 2.06 μm) as well as 250 nm Au particles, both with small size dispersions, were used in the investigations. Evaluation of the ICP-OES signals revealed good agreement between the atomic line intensities recorded with particles and droplets from standard solutions having the same analyte mass as the particles. Detection limits of spherical solid particles by ICP-OES were found to be ∼200 nm and ∼470 nm for Au and SiO₂ particles, respectively. The corresponding analyte masses at the detection limits were ∼80 fg (Au) and ∼50 fg (Si). The general applicability of the suspension technique for measurements of nanoparticles having different sizes and masses is demonstrated analyzing a suspension containing spherical SiO₂ particles of three different sizes.