Comparison of monosegmented flow analysis to flow injection for single particle inductively coupled plasma mass spectrometry

Abstract

The determination of the size and composition of nanoparticles (NPs) is important because they are increasingly prevalent in many industries. Although single particle inductively coupled plasma mass spectrometry (spICPMS) is a useful technique for the analysis of NPs, using flow injection (FI) for sample introduction simplifies the determination of NP mass by eliminating the requirements to measure the sample uptake rate and the transport efficiency. However, the dispersion that is inherent to FI degrades sensitivity and the detection limit for the simultaneous determination of dissolved analyte. To avoid this degradation, monosegmented flow analysis (MSFA) can be used, which involves the injection of a discrete volume of sample solution into a pocket of air within the carrier. This not only minimizes the dispersion experienced by the sample on the way to the nebulizer compared to when introducing the sample using FI, thereby doubling the sample throughput, but it slightly increases sample transport efficiency from 6.3% with FI-spICPMS to 8.4% with MSFA-spICPMS. This, in combination with the square-wave shape of the MSFA peak, improves sensitivity for the determination of dissolved analyte compared to FI-spICPMS, without degrading the measurement of NPs. With a 10 500 NPs mL⁻¹ suspension to avoid NPs coincidence, the size of Au NPs was measured with 0.6% relative standard deviation (RSD). On the other hand, the RSD for Pt NPs of similar size was 14% because of the higher detection limit compared to that for monoisotopic Au.