Analysis of Silver Nanoparticles Using Single-Particle Inductively Coupled Plasma – Mass Spectrometry (ICP-MS): Parameters Affecting the Quality of Results

Single-particle analysis using inductively coupled plasma mass spectrometry offers a new tool for the characterisation of inorganic nanoparticles. Its development is connected with new generations of ultrafast spectrometers. This work is concerned with thorough investigation of parameters affecting the quality of the analysis of Ag nanoparticles, i.e., nanoparticle stability, transport efficiency and sensitivity of determination. The short-term stability of Ag nanoparticles in demineralised water can be prolonged to at least 7 h by the addition of 0.05% gelatin. The sensitivity was affected by plasma power and the nebuliser Ar flow. The transport efficiency decreased with increasing sample uptake, so a compromise between the efficiency and the total number of particles entering the spectrometer should be selected. The estimate of transport efficiency is distorted when more concentrated dispersions of nanoparticles are analysed because of the overlapping of signals of multiple nanoparticles. This effect was observed for dispersions of concentration greater than 1 x 10(6) mL(-1) where an apparent decrease in transport efficiency from an initial value 7-8% to 1% was observed. The following parameters were found by method validation: concentration limit of detection of 97 mL(-1), nanoparticle diameter limit of detection 15 nm, linearity from 20 to at least 100 nm and repeatability of 1.3%. After validation, the method was applied to determine Ag nanoparticles in river water from the Vltava in Prague. Nanoparticles with diameters of 32-114 nm were found, and their number concentration increased from 340 mL(-1) to 1670 mL(-1) as the stream of water passed through urban agglomeration.