An Approach Based on an Increased Bandpass for Enabling the Use of Internal Standards in Single Particle ICP-MS: Application to AuNPs Characterization

Abstract

This paper proposes a novel approach to implement an internal standard (IS) correction in single particle inductively coupled plasma mass spectrometry (SP ICP-MS), as exemplified for the characterization of Au nanoparticles (NPs) in complex matrices. This approach is based on the use of the mass spectrometer (quadrupole) in bandpass mode, enhancing the sensitivity for the monitoring of AuNPs while also allowing for the detection of PtNPs in the same measurement run, such that they can serve as an internal standard. The performance of the method developed was proved for three different matrices: pure water, a 5 g L−1 NaCl water solution, and another water solution containing 2.5% (m/v) tetramethylammonium hydroxide (TMAH)/0.1% Triton X-100. It was observed that matrix-effects impacted both the sensitivity of the NPs and their transport efficiencies. To circumvent this problem, two methods were used to determine the TE: the particle size method for sizing and the dynamic mass flow method for the determination of the particle number concentration (PNC). This fact, together with the use of the IS, enabled us to attain accurate results in all cases, both for sizing and for the PNC determination. Additionally, the use of the bandpass mode provides additional flexibility for this characterization, as it is possible to easily tune the sensitivity achieved for each NP type to ensure that their distributions are sufficiently resolved.

Isotope Dilution Analysis for Particle Mass Determination Using Single-Particle Inductively Coupled Plasma Time-of-Flight Mass Spectrometry: Application to Size Determination of Silver Nanoparticles

“…Matrix effects can also be alleviated by sufficient sample dilution, although when the NP concentration in complex sample dispersions is already very low, this is not always practical. There are other, more general, calibration strategies dealing with these problems that have been recently adapted for use with spICP-MS, including matrix-matching [9] (as long as the matrix composition is known), standard addition [11] (usually requiring longer analysis times per sample) and internal standardization [18]; these are better or less suited depending on the application.…”

Swimming against the current – sacrificing unit mass resolution in ICP-MS to improve figures of merit

“…For instruments from Agilent Technologies the “amu gain” and “amu offset” parameters were altered to increase mass bandwidths. 6–8 For Thermo Fisher Scientific (iCAP Q) 15 and PerkinElmer (NexION 300X) 16 platforms, the scan line was altered by adapting the digital to analogue converter (“DAC”) value.…”

“…In a recent application by Bazo et al , 16 the bandpass mode was employed for internal standardisation in SP ICP-MS. Here, the bandwidth was chosen large enough to detect Au and Pt isotopes at the same time.…”

ICP-MS-Based Characterization and Quantification of Nano- and Microstructures

“…Despite considerable progress being made, SP-ICP-MS is still considered an emerging technique, with many advancements yet to come before it can be considered an established methodology. In fact, three examples of metrological advances and efforts to expand the measurement capabilities and consolidate the role of SP-ICP-MS for the characterization of NPs are included in this Special Issue [9][10][11]. The evaluation of SP-ICP-MS size uncertainty of individual NP diameter indicates that the relative uncertainty in the diameter increases as the NP size decreases regardless of the size of the NP calibration standard [9].…”

“…The cited advantages of the internal standard correction in SP-ICP-MS analysis include that the knowledge of the matrix composition is not required, avoiding pre-treatment steps to remove non-spectral interferences, and is less time consuming than standard addition and more universal than isotope dilution analysis. The novel application of isotope dilution analysis in SP-ICP-TOF-MS for the mass and size distribution determination, instead of central tendency, of silver NPs is reported [11]. The use of a TOF mass analyzer enables the simultaneous detection of 107 Ag + and 109 Ag + signals in highly diluted suspensions on a particle-by-particle basis, leading to a more precise determination of isotope ratios, which may be relevant for the analysis of complex and/or environmental samples.…”