Single Particle-Inductively Coupled Plasma-Mass Research Articles

Vast emission of Fe- and Ti-containing nanoparticles from representative coal-fired power plants in China and environmental implications

Coal combustion is considered an important source of atmospheric nanoparticles (NPs). However, the underlying information on the emission of NPs from coal-fired power plants (CFPPs) is still lacking. Along these lines, in this study, coal fly ashes (CFAs) were collected from different multi-stage particulate emission control devices (PECDs) in three representative CFPPs in China. The particle size and particle number concentration (PNC) of typical metal-containing NPs (Fe- and Ti-containing NPs) were analyzed by using the single-particle inductively coupled plasma mass (SP-ICP-MS) technology. By increasing the stage of PECDs, the mean particle sizes of NPs gradually declined and the PNCs of Fe- and Ti-containing NPs increased significantly. Specifically, the PNC of final-stage CFA was 3 - 8 times that of the first-stage CFA. A comparison of the electrostatic precipitators (ESPs), fabric filters (FFs), and electrostatic-fabric-integrated precipitators (EFIPs) showed that the state-of-the-art EFIPs exhibited a relatively good NP-removal efficiency with the highest PNCs. In addition, NP hourly emissions in all coal combustion by-products (CCPs) were further calculated in a typical CFPP. The total emissions of Fe- and Ti-containing NPs in all CCPs were 1.87 × 1018 and 1.57 × 1018 particles/h, respectively. NPs were mainly enriched in CFA trapped by PECDs (80% of total emissions). Although the mass of the CFA that escaped through the stack was extremely low, it contained the highest PNCs of Fe- and Ti-containing NPs of all CCPs, accounting for 3.41% and 1.67% of the corresponding total NP emissions. These NPs may also coexist with various toxic metals, such as Zn and Pb, and be released directly into the atmosphere, where they pose a potential risk to human health.

Size Dependent Dissolution of Silver Nanoparticles in Human Monocytic/Macrophage-Like U937 Cells and Speciation by Single Particle-Inductively Coupled Plasma-Mass Spectrometry (SP-ICP-MS)

Various analytical methods have been employed to assess the nanoparticle (NP) toxicity and to better understand cell interactions. In this study, a rapid single particle – inductively coupled plasma – mass spectrometry (SP-ICP-MS) method is utilized to evaluate silver nanoparticle (AgNP) uptake by human monocytic/macrophage-like U937 cells. For this purpose, the cells were incubated with 40 nm and 70 nm AgNPs at 100 and 1000 ng mL−1 for 48 h. After cells were incubated with 40 nm and 70 nm AgNPs at the lower dosage (100 ng mL−1), the silver mass per cell was determined to be 1.5 ± 0.1 fg/cell (approximately 4 nanoparticles) and 3.6 ± 0.1 fg/cell (approximately 2 nanoparticles), respectively. Furthermore, for 100 ng mL−1 AgNP exposure, the results showed that silver was present both in the medium and in cell lysate only as AgNP. However, when cells were treated with 40 nm and 70 nm AgNPs at 1000 ng mL−1, approximately 10% and 40% of the total Ag concentration in cell lysate were AgNP and the rest was Ag+, while AgNP was the only species in the medium. The results show that 40 nm AgNP dissolved significantly more in cells compared to 70 nm AgNP. Moreover, ultracentrifugation, ICP-MS, and field emission scanning electron microscopy (FE-SEM) were employed with scanning transmission electron microscopy (STEM) to validate and confirm the SP-ICP-MS results.

Development and Application of Nanoparticle-Nanopolymer Composite Spheres for the Study of Environmental Processes.

Plastics have long been an environmental contaminant of concern as both large-scale plastic debris and as micro- and nano-plastics with demonstrated wide-scale ubiquity. Research in the past decade has focused on the potential toxicological risks posed by microplastics, as well as their unique fate and transport brought on by their colloidal nature. These efforts have been slowed by the lack of analytical techniques with sufficient sensitivity and selectivity to adequately detect and characterize these contaminants in environmental and biological matrices. To improve analytical analyses, microplastic tracers are developed with recognizable isotopic, metallic, or fluorescent signatures capable of being identified amidst a complex background. Here we describe the synthesis, characterization, and application of a novel synthetic copolymer nanoplastic based on polystyrene (PS) and poly(2-vinylpyridine) (P2VP) intercalated with gold, platinum or palladium nanoparticles that can be capped with different polymeric shells meant to mimic the intended microplastic. In this work, particles with PS and polymethylmethacrylate (PMMA) shells are used to examine the behavior of microplastic particles in estuarine sediment and coastal waters. The micro- and nanoplastic tracers, with sizes between 300 and 500 nm in diameter, were characterized using multiple physical, chemical, and colloidal analysis techniques. The metallic signatures of the tracers allow for quantification by both bulk and single-particle inductively-coupled plasma mass spectrometry (ICP-MS and spICP-MS, respectively). As a demonstration of environmental applicability, the tracers were equilibrated with sediment collected from Bellingham Bay, WA, United States to determine the degree to which microplastics bind and sink in an estuary based of grain size and organic carbon parameters. In these experiments, between 80 and 95% of particles were found to associate with the sediment, demonstrative of estuaries being a major anticipated sink for these contaminants. These materials show considerable promise in their versatility, potential for multiplexing, and utility in studying micro- and nano-plastic transport in real-world environments.

Cloud point extraction (CPE) combined with single particle -inductively coupled plasma-mass spectrometry (SP-ICP-MS) to analyze and characterize nano-silver sulfide in water environment

Silver Nanoparticles (Ag-NPs), an emerging type of pollutant, might occur various physical and chemical transformations, which would affect its environmental fate, transformation and biological effects. Sulfurization is the most common conversion of Ag-NPs, accompanied by the formation of nano-silver sulfide (Ag2S-NPs). The method of Ag2S-NPs analysis and characterization is of great significance for assessing the environmental risks of Ag. In this study, cloud point extraction (CPE) and Single Particle-Inductively Coupled Plasma-Mass Spectrometry (SP-ICP-MS) were used in combination to establish a simple and reliable analysis method to quantify Ag2S-NPs in water, with the morphology unchanged. Non-Ag2S-NPs were dissociated into Ag+ firstly, and Ag2S-NPs and Ag+ were separated by CPE, followed by SP-ICP-MS analysis. The extraction rate based on particle number concentration was between (76.19 ± 0.56) % to (106.35 ± 0.00) % in environmental waters. Compared with the (76.96 ± 2.18) nm Ag2S-NPs spiked, the particle size extracted increased slightly with (94.19 ± 2.72) nm- (97.25 ± 0.22) nm as the large-size Ag2S-NPs originally presented in waters, instead of agglomeration. This method could be generally applicable to the analysis of Ag2S-NPs in waters, and provide ideas for other metal sulfide nanoparticles (MS-NPs), which has certain significance.

Optimization of instrumental parameters for improving sensitivity of single particle inductively-coupled plasma mass spectrometry analysis of gold

Single particle inductively-coupled plasma mass spectrometry (spICP-MS) is a promising technique for analysis of engineered nanoparticles, whose utilization has increased substantially over the past years. Optimization of instrumental conditions is, however, crucial to improve the sensitivity and precision of nanoparticle (NP) detection. In this study, the influence of ICP-MS instrumental parameters (nebulizer gas flow, plasma radiofrequency-power and sampling depth) on the signal intensity of gold in spICP-MS was evaluated using dispersions of Au NPs and a solution of dissolved gold. The interaction effects of the main factors were found to have a significant effect on the signal intensity, proving that factor values should be jointly optimized instead of one at a time, if maximum ion signal is expected. Optimization of instrumental parameter values was performed for both analyte forms and found to be in a good agreement, indicating a similar behavior of the particles in plasma compared with the dissolved analyte. However, some differences in the behavior of the two analyte forms as regard to sampling depth position was observed. Particle size or the presence of complex sample matrix was not found to influence the optimal instrumental parameter values, however, a significant signal depression for gold was observed (up to 50%) in matrices containing high levels of sodium. Compared to frequently used ‘robust conditions’, a 70% increase in the ion signal intensity of gold and a 15% decrease in the particle size detection limit was achieved with instrumental parameter optimization. As such, instrumental parameter optimization for sensitive NP analysis can be seen as highly beneficial procedure.

Accurate Determination and Characterization of Gold Nanoparticles Based on Single Particle-Inductively Coupled Plasma-Mass Spectrometry

Abstract An accurate determination method for gold nanoparticles (AuNPs) number concentration and size was developed based on single particle-inductively coupled plasma-mass spectrometry (SP-ICP-MS). Influencing parameters such as different calculation methods of transport efficiency, dwell time, dispersing agent and injection mode were investigated and optimized. The transport efficiency has a greater impact on the accuracy of the measurement result, and it should be selected according to the measured target parameters. It was important to keep the stability of the transport efficiency and use the calibration standard calibrating during the measurement process. The dwell time directly affected the precision of result, and the data processing mode should be selected carefully according to the sample type, particle size and other properties. When the dwell time was 0.1 ms, the linear ranges of 30 nm and 60 nm AuNPs were 2–40 pg/g and 10–200 pg/g, respectively, the linear correlation coefficient was greater than 0.9998, the relative standard deviation was less than 3.80%. The detection limits of particle number concentration and particle size were 110 NPs/g and 9 nm, respectively. Four kinds of synthesized AuNPs and international pilot study sample were determined by the established method. The deviation of the number concentration in pilot study from the key comparison reference values was less than 5%. The results were equivalent and the expanded uncertainty was less than 15% (k = 2), which further verified the accuracy and applicability of the method.

Nanoparticle Characterisation of Traditional Homeopathically Manufactured Cuprum metallicum and Gelsemium sempervirens Medicines and Controls.

Homeopathy is controversial due to its use of very highly diluted medicines (high potencies/dynamisations). We used a multi-technology approach to examine dilutions of two commonly used homeopathic medicines: an insoluble metal, Cuprum metallicum, and a soluble plant tincture, Gelsemium sempervirens, for the presence of nanoparticles (NPs) of original substance. The homeopathic medicines tested were specially prepared, according to the European pharmacopoeia standards. We compared the homeopathic dilutions/dynamisations with simple dilutions and controls. Using Mass Spectrometry (Single Particle-Inductively Coupled Plasma-Mass Spectrometry) and Dynamic Light Scattering (DLS) we could not find the expected copper in the 4cH potentisation and could not confirm the results previously obtained by Chikramane et al (2010). For Gelsemium medicines, using sensitive chromatography (HPLC-UV) up to a dilution level of 6 dH (3cH = dilution 10e-6), there was no significant difference in alkaloid content between a simple dilution and a homeopathic potency.For higher potentisations, however, NP tracking analysis findings revealed the presence of particles in all samples (except for pure water). The measurements showed large differences in particle quantities, mean particle sizes and standard deviations of the mean sizes between manufacturing lines of different starting material.There was always more material in potentised medicines than in potentised pure water. Gelsemium yielded the largest quantity of material (36 times more than that from copper at the same potentisation, 30 cH). The shapes and the chemical composition of the material are differentiable between different medicines and controls. Potentisation influences specifically the nature of NPs detected. This material demonstrates that the step-by-step process (dynamised or not) does not match with the theoretical expectations in a dilution process. The Avogadro/Loschmidt limit is not relevant at all. It was not possible to reproduce the findings of Chikramane et al (2010) using inductively coupled plasma-mass spectrometry with copper. Copper NPs could not be detected at 4cH and above.

Screening of TiO2 and Au nanoparticles in cosmetics and determination of elemental impurities by multiple techniques (DLS, SP-ICP-MS, ICP-MS and ICP-OES)

Cosmetics are part of the daily life of most of the people. Thus, a complete characterization of the products we applied in our skin is necessary. In this work, an analytical investigation of a wide variety of cosmetics from the point of view of total element content and metallic nanoparticles (NPs) has been performed. Firstly, we analyzed the total element content by ICP-MS and ICP-OES after acid digestion as an assessment of the presence of metal impurities. Prohibited elements in cosmetics, according to the European Commission regulation No 1223/2009, were not detected, and only elements mentioned in the label were found (e.g. Al, Fe, Ti and Si). Secondly, a screening of the presence of NPs has been performed by Dynamic Light Scattering (DLS) and Single Particle Inductively-Coupled Plasma Mass Spectrometry (SP-ICP-MS). Two sample preparation procedures were applied. The first protocol consisted in the preparation of suspensions in 0.1% w/v SDS and the second based on defatting with hexane followed by resuspension in water. DLS was employed as a routine method for a fast analysis of NPs, but this technique showed limitations due to the lack of specificity. SP-ICP-MS analyses were then performed, first as a screening technique to evaluate the presence of TiO2 and Au NPs in cosmetics suspensions prepared in SDS; and second, when a positive answer was obtained about the presence of NPs from the screening, SP-ICP-MS was used for particle size determination. Results showed that only TiO2 NPs were present in two sunscreens, one anti-wrinkle day cream, one lip balm protector labeled as ‘nano’ and in one brand of toothpaste not labeled as ‘nano’. Sizes obtained for both sample preparations were compared and ranged from 30 to 120nm in most of the samples.

Single Particle-Inductively Coupled Plasma Mass Spectroscopy Analysis of Metallic Nanoparticles in Environmental Samples with Large Dissolved Analyte Fractions.

There is an increasing interest to use single particle-inductively coupled plasma mass spectroscopy (SP-ICPMS) to help quantify exposure to engineered nanoparticles, and their transformation products, released into the environment. Hindering the use of this analytical technique for environmental samples is the presence of high levels of dissolved analyte which impedes resolution of the particle signal from the dissolved. While sample dilution is often necessary to achieve the low analyte concentrations necessary for SP-ICPMS analysis, and to reduce the occurrence of matrix effects on the analyte signal, it is used here to also reduce the dissolved signal relative to the particulate, while maintaining a matrix chemistry that promotes particle stability. We propose a simple, systematic dilution series approach where by the first dilution is used to quantify the dissolved analyte, the second is used to optimize the particle signal, and the third is used as an analytical quality control. Using simple suspensions of well characterized Au and Ag nanoparticles spiked with the dissolved analyte form, as well as suspensions of complex environmental media (i.e., extracts from soils previously contaminated with engineered silver nanoparticles), we show how this dilution series technique improves resolution of the particle signal which in turn improves the accuracy of particle counts, quantification of particulate mass and determination of particle size. The technique proposed here is meant to offer a systematic and reproducible approach to the SP-ICPMS analysis of environmental samples and improve the quality and consistency of data generated from this relatively new analytical tool.

Influences of Primary Particle Size, Concentration, Ionic Species, and Aggregation States on Transport Efficiency in Single Particle-Inductively Coupled Plasma-Mass Spectrometry Analysis of Metal-Based Nanoparticles

Influences of Primary Particle Size, Concentration, Ionic Species, and Aggregation States on Transport Efficiency in Single Particle-Inductively Coupled Plasma-Mass Spectrometry Analysis of Metal-Based Nanoparticles

Rapid determination of plasmonic nanoparticle agglomeration status in blood

Plasmonic nanomaterials as drug delivery or bio-imaging agents are typically introduced to biological systems through intravenous administration. However, the potential for agglomeration of nanoparticles in biological systems could dramatically affect their pharmacokinetic profile and toxic potential. Development of rapid screening methods to evaluate agglomeration is urgently needed to monitor the physical nature of nanoparticles as they are introduced into blood. Here, we establish novel methods using darkfield microscopy with hyperspectral detection (hsDFM), single particle inductively-coupled plasma mass spectrometry (spICP-MS), and confocal Raman microscopy (cRM) to discriminate gold nanoparticles (AuNPs) and their agglomerates in blood. Rich information about nanoparticle agglomeration in situ is provided by hsDFM monitoring of the plasmon resonance of primary nanoparticles and their agglomerates in whole blood; cRM is an effective complement to hsDFM to detect AuNP agglomerates in minimally manipulated samples. The AuNPs and the particle agglomerates were further distinguished in blood for the first time by quantification of particle mass using spICP-MS with excellent sensitivity and specificity. Furthermore, the agglomeration status of synthesized and commercial NPs incubated in blood was successfully assessed using the developed methods. Together, these complementary methods enable rapid determination of the agglomeration status of plasmonic nanomaterials in biological systems, specifically blood.

Characterization and Determination of Silver Nanoparticle Using Single Particle-Inductively Coupled Plasma-Mass Spectrometry

Abstract A single particle-inductively coupled plasma mass spectrometry (SP-ICP-MS) method was established to detect the size distribution and number concentrations of silver nanoparticles (AgNPs) in dilute aqueous solution. The optimal dwell time was 3 ms to reduce possibility of two or more particles entering simultaneously into detector. An iterative algorithm was applied to distinguish AgNPs as outliers from baseline and dissolved metal ion signal if measured intensity was beyond five time standard deviation of whole data. The size distribution and number concentration of three commercial silver nanoparticle dispersions (nominal diameters of 30, 50 and 100 nm) were determined by SP-ICP-MS. The result of SP-ICP-MS was accurately similar to that of TEM, indicating that SP-ICPMS could be used to detect silver nanoparticles. The particle size detection limit was 25 nm and the limit of number concentration was 8 × 104 particles L−1 in dilute solution. Tap water being added with silver nanoparticles was tested to obtain a similar size distribution and number concentration. This method was simple, fast and highly sensitive, and quite feasible to investigate the risk assessment of silver nanoparticles in aqueous environment and monitor silver nanoparticles in drinking water.

Hydrodynamic Chromatography Coupled with Single Particle-Inductively Coupled Plasma Mass Spectrometry for Investigating Nanoparticles Agglomerates

Studying the environmental fate of engineered or natural colloids requires efficient methods for measuring their size and quantifying them in the environment. For example, an ideal method should maintain its correctness, accuracy, reproducibility, and robustness when applied to samples contained in complex matrixes and distinguish the target particles from the natural colloidal background signals. Since it is expected that a large portion of nanoparticles will form homo- or heteroagglomerates when released into environmental media, it is necessary to differentiate agglomerates from primary particles. At present, most sizing techniques do not fulfill these requirements. In this study, we used online coupling of two promising complementary sizing techniques: hydrodynamic chromatography (HDC) and single-particle ICPMS analysis to analyze gold nanoparticles agglomerated under controlled conditions. We used the single-particle mode of the ICPMS detector to detect single particles eluted from an HDC-column and determine a mass and an effective diameter for each particle using a double calibration approach. The average agglomerate relative density and fractal dimension were calculated using these data and used to follow the morphological evolution of agglomerates over time during the agglomeration process. The results demonstrate the ability of HDC coupled to single-particle analysis to identify and characterize nanoparticle homoagglomerates and is a very promising technique for the analysis of colloids in complex media.

Hydrodynamic Chromatography Online with Single Particle-Inductively Coupled Plasma Mass Spectrometry for Ultratrace Detection of Metal-Containing Nanoparticles

Nanoparticle (NP) determination has recently gained considerable interest since a growing number of engineered NPs are being used in commercial products. As a result, their potential to enter the environment and biological systems is increasing. In this study, we report on the development of a hyphenated analytical technique for the detection and characterization of metal-containing NPs, i.e., their metal mass fraction, size, and number concentration. Hydrodynamic chromatography (HDC), suitable for sizing NPs within the range of 5 to 300 nm, was coupled online to inductively coupled plasma mass spectrometry (ICPMS), providing for an extremely selective and sensitive analytical tool for the detection of NPs. However, a serious drawback when operating the ICPMS in its conventional mode is that it does not provide data regarding NP number concentrations and, thus, any information about the metal mass fraction of individual NPs. To address this limitation, we developed single particle (SP) ICPMS coupled online to HDC as an analytical approach suitable for simultaneously determining NP size, NP number concentration, and NP metal content. Gold (Au) NPs of various sizes were used as the model system. To achieve such characterization metrics, three calibrations were required and used to convert ICPMS signal spikes into NPs injected, NP retention time on the HDC column to NP size, and ions detected per signal spike or per NP to metal content in each NP. Two calibration experiments were required in order to make all three calibrations. Also, contour plots were constructed in order to provide for a convenient and most informative viewing of this data. An example of this novel analytical approach was demonstrated for the analysis of Au NPs that had been spiked into drinking water at the ng Au L(-1) level. The described technique gave limits of detection for 60 nm Au NPs of approximately 2.2 ng Au L(-1) or expressed in terms of NP number concentrations of 600 Au NPs mL(-1). These were obtained while the 60 nm NPs exhibited a retention time of 771 s at a mobile phase flow rate of 1 mL min(-1).