Critical considerations for the determination of nanoparticle number concentrations, size and number size distributions by single particle ICP-MS

Abstract

The metrological criteria for the implementation of the single particle inductively coupled plasma mass spectrometry (SP-ICPMS) methodology applied to nanoparticle size characterization and quantification have been investigated. The SP-ICPMS basis involves a process of counting events corresponding to individual nanoparticles, which requires (i) isolation of the contribution of the nanoparticles from that of the background/dissolved analyte, and (ii) avoiding the occurrence of multiple-nanoparticle events. A criterion based on three times the standard deviation of the continuous background (3s) was selected as the threshold for discrimination of nanoparticle events from the background. Because the detectability of nanoparticles depends on both the size and number concentration, this 3s criterion was also selected for detection of nanoparticles at the size detection limit and concentrations over the number concentration detection limit. However, at very low number concentrations, a less restrictive criterion must be used. The selection of a critical nanoparticle number concentration, based on the sample introduction and data acquisition parameters, allows the minimization of the occurrence of multiple-nanoparticle events, as well as controlling of the precision associated with the counting of nanoparticle events. Under such conditions, the standard uncertainty associated with the determination of number concentrations was 5%. The uncertainty for the determination of nanoparticle diameters was also studied, varying from 3 to 10% for diameters in the range of 100–40 nm, respectively. Reliable average number concentrations and sizes were obtained, although the number size distributions showed a significant broadening contribution due to the SP-ICPMS measurement process. The feasibility of SP-ICPMS for the implementation of the European Commission definition of "nanomaterial" was studied by analyzing commercial silver nanoparticle suspensions

Detection, characterization and quantification of inorganic engineered nanomaterials: A review of techniques and methodological approaches for the analysis of complex samples

“…Number concentration detection limits in the range of 1000 particles per mL can be achieved [118], whereas lowest size detection limits are in the range of 10-20 nm for monoelemental nanoparticles or more than 100 nm for oxides [119]. Although SP-ICP-MS shows a great potential for NP analysis, the presence of dissolved species of the monitored element can hinder or even make impossible the detection of the NPs.…”

Analytical Developments for the Characterization of Nanomaterials in Consumer Products, Environmental and Medicinal Samples

“…A4F techniques can also be hyphenated with ICP-MS to obtain information about NPs composition. More recently, Single-Particle Inductively Coupled Plasma Mass Spectrometry (SP-ICP-MS) has been used to quantify the number, concentration and size of NPs by using the frequency of analytical signals and the relationship between mass and density, respectively [15]. This technique is gaining more and more importance, especially on a routine basis due to its rapidity [16,17].…”

Double-Viewing-Position Single-Particle Inductively Coupled Plasma-Atomic Emission Spectrometry for the Selection of ICP Sampling Position in SP-ICP Measurements

“…[20][21][22][23][24][25] SP-ICP-MS is sensitive; gold and silver nanoparticles of diameter as small as 10 nm are readily detected. [26][27][28][29] Quantitative analysis is best achieved by calibration using standard particles, 6,28,30 although standard-solution calibration is commonly used due to limited availability of standard particles. 1,31 The basic assumption of the standard-solution calibration method is that ICP-MS intensity depends only on the mass flux of the analyte, irrespective of the original states of the analyte.…”