Single-particle ICP-MS with online microdroplet calibration: toward matrix independent nanoparticle sizing. Issue 4 (15th January 2019)

• Record Type: Journal Article
• Authors: Hendriks, Lyndsey; Ramkorun-Schmidt, Benita; Gundlach-Graham, Alexander; Koch, Julian; Grass, Robert N.; Jakubowski, Norbert; Günther, Detlef
• Is Part Of: Journal of analytical atomic spectrometry. Volume 34:Issue 4(2019)
• Page Start: 716
• Page End: 728
• Publication Date: 2019-01-15
• Subjects: Atomic spectra -- Periodicals; Atomic absorption spectroscopy -- Periodicals; 543.0858
• DOI: 10.1039/c8ja00397a
• Languages: English
• ISSNs: 0267-9477

Abstract

Abstract : Microdroplets with known concentrations of element standards are introduced concomitant with NP-containing solutions into the ICP to provide online matrix-matched calibration of analyte NPs for single-particle-ICP-TOFMS. Abstract : Single-particle inductively coupled plasma mass spectrometry ( sp -ICP-MS) has become an effective tool for the detection and quantification of inorganic nanoparticles (NPs). While sizing of NPs suspended in water is relatively straightforward by sp -ICP-MS, accurate mass quantification of NPs in complex media, such as consumer products and natural systems still remains a challenge. When NPs are suspended in a complex medium, the matrix may affect the analyte sensitivity and lead to inaccurate NP sizing. Here, we investigate the use of an online microdroplet calibration system to size NPs in a single step. In this setup, microdroplets—which are used as the calibrant to determine elemental sensitivities—and nebulized NP-containing solutions are introduced concurrently into the ICP via a dual-inlet sample introduction system. Because calibrant microdroplets and analyte NPs experience the same plasma conditions, both the microdroplets and the NPs are subjected to the same matrix-related signal enhancement or suppression. In this way, the microdroplet calibration standards are automatically matrix matched with the NP-containing solution. The online microdroplet calibration system is combined with an ICP-TOFMS instrument for simultaneous measurement of multiple elements in microdroplets and NPs. We investigate the ability of online microdroplet calibration to compensate for matrix effects through a series of experiments, in which Ag and Au NPs are measured with variable plasma-sampling positions, varying concentrations of HCl and HNO3, varying concentrations of single element solutions, and high concentrations of a salt matrix, i.e. phosphate buffered saline (PBS). Through these experiments, we demonstrate that the online microdroplet calibration strategy provides a matrix-independent mass quantification of analyte NPs in the presence of several established types of matrix effects, including acid effects, space-charge effects, and ionisation suppression. In results presented here, we focus on the size determination of the NPs.