Performance of sp-ICP-TOFMS with signal distributions fitted to a compound Poisson model

Abstract

Characterization of dissolved background signals as compound Poisson distributed enables more accurate and robust nanoparticle detection thresholds in single-particle ICP-TOFMS.

Single-particle ICP-TOFMS with online microdroplet calibration for the simultaneous quantification of diverse nanoparticles in complex matrices

“…In our Matlab script, microdroplet signals were isolated from data traces by their multi-element fingerprints, and NPs were identified based on a critical value detection criterion (S C ) that gives a false-positive rate of 0.01%; critical values were based on modelling TOFMS signals as a compound Poisson signal distribution. 32,34 Prior to data analysis in Matlab, TOF spectra were mass calibrated in TOFWARE (ver. 2.5.11, TOFWERK, run in Igor-Pro 7 environment) and exported as .CSV time traces of counts vs. time for all analyte isotopes.…”

“…Au, Pt, and Ag) and endogenous particles present in the WWTP effluent sample. All NP signals were found by fitting m/z-specific background signals with a compound Poisson distribution 32,34 and then thresholding ICP-TOFMS data at a critical value (S C ) that predicts 0.01% false-positive particle signals. As seen, the determined d eff,i, and PNC values of the spiked engineered NPs match well with expectation.…”

Monodisperse microdroplets: a tool that advances single-particle ICP-MS measurements

“…This setup has been described elsewhere. 33,[35][36][37][38]40,41 In this setup, microdroplets are produced by a microdroplet generator (50 mm diameter Autodrop Pipette, AD-KH-501-L6, MD-E-3000 dispensing system, Microdrop Technologies, GmbH, Germany) and introduced via a falling tube that is lled with a He/ Ar gas mixture to accelerate solvent evaporation so that microdroplets are reduced to dried droplet residues by the end of the falling tube. 26,42 Continuously nebulized samples are introduced via a pneumatic nebulizer and spray chamber, and then mixed with microdroplet-aerosols via a t-piece just in front of the injector base of the ICP torch.…”

“…59,72 For ICP-TOFMS, we have shown that ion signals are neither Gaussian nor Poisson distributed; instead, signals follow a compound-Poisson distribution that is the result of Poissondistributed ion arrival and the response function of the electron-multiplier detection system. 40,41 Because distributions of ICP-TOFMS signals have a unique compound-Poisson shape, accurate separation of background signals from particle signals requires a distinct critical value, L C(ADC) , that is calculated via Monte Carlo methods. 40 L C(ADC) is the net-signal critical value, i.e.…”

Emerging investigator series: automated single-nanoparticle quantification and classification: a holistic study of particles into and out of wastewater treatment plants in Switzerland

“…A detailed explanation of each of these data processing steps is beyond the scope of this reportin part because many aspects of the analysis strategy are reported elsewhere. 36,[38][39][40][41][42] For aspects of this process that are new to the current study, we provide a more detailed discussion below. In addition, our "NanoFinder" software is provided under an open-source license (http://doi.org/10.5905/ethz-1007-363) and is hosted at https://github.com/ethz-tema/TEMAsingleParticle.…”