Integrating Instead of Averaging Signal Intensity to Simplify Nanoparticle Mass Measurement by Single Particle Inductively Coupled Plasma Mass Spectrometry

The use of single particle inductively coupled plasma mass spectrometry has been rapidly expanding for the analysis of nanoparticles (NPs). When external calibration with standard solutions is done to find the mass of NPs, the average signal intensity for each standard solution is typically used, which requires measurement of the transport efficiency of solutions through the spray chamber. However, if the signal is integrated over a constant time period for all standards and samples, then there is no need to determine the transport efficiency to measure NP mass, as the mass of analyte aspirated can be directly found by multiplying the analyte concentration in each standard by the sample uptake rate and the integration time. The line of best fit through the calibration curve of integrated signal versus mass is then used to find the total mass of NPs nebulized during the integration time, the mass of each NP then corresponding to the fraction of the total integrated signal caused by the NP. Measurement of the transport efficiency is only required if the concentration of NPs is desired.