Characterization of single Au and SiO2 nano- and microparticles by ICP-OES using monodisperse droplets of standard solutions for calibration

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 mm) 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 similar to 200 nm and similar to 470 nm for Au and SiO2 particles, respectively. The corresponding analyte masses at the detection limits were similar to 80 fg ( Au) and similar to 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.