After more than ten years of steady development of single particle inductively coupled plasma mass spectrometry (SP-ICP-MS), it seems a good time to seek consensus about some metrological issues in relation to the technique. Making our results comparable requires a certain level of agreement in the SP-ICP-MS community on theoretical (e.g., threshold criteria for discrimination of particles from baseline) and practical topics (e.g., determination of transport efficiency), but also the availability of reliable tools for their application.

Whereas first SP-ICP-MS methods were based on the use of millisecond dwell times, faster instruments allowed working with dwell times in the microsecond range. When data acquisition frequency is increased, individual particles are recorded as peaks consisting of multiple reading events, making data processing more complex and requiring the integration of different analysis tools on the software, in line with those used for chromatograms. Precisely, the use of different proprietary software provided by most manufacturers for data treatment, make results not comparable until this software is harmonized and validated. In this regard, the availability of open-access software (SPCal) [1] for processing of SP-ICP-MS data could contribute to such process, if criteria are clearly defined. In addition, the capability of these software for data processing regardless of the acquisition frequency applied, make possible to work in the transition region between pulses and peaks, managing with consecutive pulses and removing the fictitious border between these two situations stablished at the beginning.

In this work, different topics will be presented and discussed: (i) the inter-validation of a manufacturer software and the open-access software SPCal by applying appropriate thresholding criteria. (ii) the detection of particle events with respect to dwell time from milli seconds to microseconds under different conditions (iii) the reliability of methods for estimating transport efficiencies to be used in particle size (or element mass per particle) and number concentration determinations.


References

[1] T.E. Lockwood; R. Gonzalez De Vega; D. Clases J. Anal. At. Spectrom. 2021, 36, 2536.


Acknowledgments
This work was supported by the project PID2021-123203OB-I00 funded by MCIN/AEI/10.13039/501100011033 and by “ERDF A way of making Europe” and the Government of Aragon (E29_23R). I. A. thanks the European Union-Next Generation EU and the Spanish Ministry of Universities for funding under the María Zambrano Grant (MZ-240621).