Post hoc Interlaboratory Comparison of Single Particle ICP-MS Size Measurements of NIST Gold Nanoparticle Reference Materials

Abstract

Single particle inductively coupled plasma-mass spectrometry (spICP-MS) is an emerging technique that enables simultaneous measurement of nanoparticle size and number quantification of metal-containing nanoparticles at realistic environmental exposure concentrations. Such measurements are needed to understand the potential environmental and human health risks of nanoparticles. Before spICP-MS can be considered a mature methodology, additional work is needed to standardize this technique including an assessment of the reliability and variability of size distribution measurements and the transferability of the technique among laboratories. This paper presents the first post hoc interlaboratory comparison study of the spICP-MS technique. Measurement results provided by six expert laboratories for two National Institute of Standards and Technology (NIST) gold nanoparticle reference materials (RM 8012 and RM 8013) were employed. The general agreement in particle size between spICP-MS measurements and measurements by six reference techniques demonstrates the reliability of spICP-MS and validates its sizing capability. However, the precision of the spICP-MS measurement was better for the larger 60 nm gold nanoparticles and evaluation of spICP-MS precision indicates substantial variability among laboratories, with lower variability between operators within laboratories. Global particle number concentration and Au mass concentration recovery were quantitative for RM 8013 but significantly lower and with a greater variability for RM 8012. Statistical analysis did not suggest an optimal dwell time, because this parameter did not significantly affect either the measured mean particle size or the ability to count nanoparticles. Finally, the spICP-MS data were often best fit with several single non-Gaussian distributions or mixtures of Gaussian distributions, rather than the more frequently used normal or log-normal distributions.

Considerations of Environmentally Relevant Test Conditions for Improved Evaluation of Ecological Hazards of Engineered Nanomaterials

“…32, 230, 252-254 Also, detection methods for ENMs in environmental media and distinguishing ENMs from natural chemical analogs are still under development, 161, 255-257 with more evaluation strategies needed including a framework for validating new ENM analytical detection methods. 215 Fullerenes from incidental sources (combustion products) were quantified in river sediments collected from locations across the globe 258 and quantified in the atmosphere over the Mediterranean Sea.…”

Overcoming challenges in single particle inductively coupled plasma mass spectrometry measurement of silver nanoparticles

“…In recent years, this method and its application have evolved rapidly, with progress in metrological criteria [10–14], data acquisition [15] and processing [16–19], experimental methodology [20–23], as well as instrumentation [24, 25]. However, challenges remain with respect to obtaining accurate and consistent measurements of size, size distribution, and number concentration using spICP-MS [26], while appropriate validation studies are scarce.…”

Impact of and correction for instrument sensitivity drift on nanoparticle size measurements by single-particle ICP-MS

“…Importantly, spICP-MS is sufficiently sensitive to measure nano-objects, including NPs, at environmentally relevant concentrations (parts per trillion mass concentrations). Several factors (e.g., signal dwell time, background correction algorithm, split-particle events, and nebulization transport efficiency) are known to influence the accuracy of spICP-MS measurements [28]. While some strategies to address such factors have been formulated, many improvements remain to be made [29–32].…”