Quantifying the Multi-Element Composition of Single Steel Nanoparticles with the icpTOF: Application Note

Simultaneous measurement of all isotopes enables quantitative determination of the multi-elemental composition of complex single particles.

Olga Borovinskaya, Steffi Boehme
TOFWERK, RIKILT, The Netherlands

Single particle inductively coupled plasma mass spectrometry (sp-ICP- MS) has established itself as a robust and sensitive method for the measurement of nanoparticle size and number concentration at environmentally relevant levels. A single particle transmitted into an ICP- mass spectrometer generates a ~1 ms pulse of ion signal (e.g., Figure a). Most ICP- mass spectrometers use sequential mass analyzers that can measure only one or two isotopes during this rapid single-particle detection event. This is insufficient for the detection of complex multi-element particles, which represent a substantial portion of manufactured nanomaterials used as additives in consumer products or which are formed by chemical modifications of pristine single-element particles after they have entered the natural environment.

The TOFWERK icpTOF simultaneously measures all isotopes, enabling determination of the complete chemical composition of single nanoparticles. In a previous application note (Multi-element Detection of Nanoparticles with icpTOF, 2016), we demonstrated the ability of the icpTOF to record all elements in single particles and compared multi-element icpTOF data to what can be recorded with modern sequential mass analyzers. Here, we show that the elemental composition of single steel nanoparticles in a polydisperse population can be quantified based on a simple multi-element solution calibration.

Determining the elemental composition of single steel nanoparticles. Steel nanoparticles (IRMM-383) synthesized in the frame of the NanoDefine Project (http://www.nanodefine.eu/index.php/project-overview) were provided by Steffi Böhme. Complete mass spectra (all isotopes) of single particles were recorded with the icpTOF using H2 in the Q-cell to reduce the interference of ArO+ and ArC+ with 56Fe+and 52Cr+, respectively. Figure a) shows the transient signal of Cr, Fe, Ni, and Mo from a single particle and figure b) the signals of many single particles recorded in a 20 second time period. The response of the icpTOF to individual elements figure c) was calibrated using standard solutions of Cr, Fe, Ni, and Mo in 1 % nitric acid in the concentration range of 0.1 -1 0 mg/g. This calibration was used to determine the concentration (c) of each element in every single particle, and element fractions for each particle were calculated using 100 % normalization method (c(Fe)+c(Cr)+c(Ni)+c(Mo)=100%). The table compares element fractions used for synthesis of these particles to the mean element fractions of 1900 single particles measured with the icpTOF.
Share on facebook
Share on twitter
Share on linkedin
ASK A QUESTION
close slider
Contact Us Pop Up

We would like to hear from you. Please send us a message by filling out the form below or email mail@tofwerk.com, and we will get back with you shortly.