Sp ICP-MS Research Articles

Studying the degradation of bulk PTFE into microparticles via SP ICP-MS: a systematically developed method for the detection of F-containing particles

Investigating the degradation of PTFE in seawater after UV radiation by SP ICP-MS via F and C analysis.

A SP-ICP-MS protocol for the detection of metal nanoparticles composition and size in tattooed ex vivo human skin explants

We developed and validated a protocol based on Single Particle Inductively Coupled Plasma Mass Spectrometry (SP ICP-MS) to detect composition and size of metal nanoparticles (MNPs) in tattoo inks end ex vivo tattooed human skin explants. The explants were tattooed with different inks using an ordinary tattoo machine. Then, 72 hours after tattooing, skin explants were subjected to alkaline extraction by tetramethylammonium hydroxide solution and MNPs of Ag, Al2O3, Au, Cr2O3, CuO, Fe2O3, TiO2 and ZnO were analysed for particle composition and size by SP ICP-MS. The method was validated by assessing the limit of detection, accuracy, precision, and size stability over 72 hours. Particles of Al2O3, Cr2O3, CuO, Fe2O3, TiO2 and ZnO were observed in human skin in the range from 27 nm to 153 nm, and from 26 nm to 228 nm in tattoo inks. Ag and Au NPs were not found neither in inks nor in the skin. Advantages of the protocol were the ability to simultaneously detect the composition of particles and their size, the straightforward sample preparation, the high sensitivity and precision, and the speed of execution of the analysis. The developed methodology can be applied to skin exposed to other consumer products topically applied, such as sunscreens, cosmetics, personal care products and medical devices, which can be all sources of MNPs, in order to improve knowledge and support the human exposure assessment process.

A green and fast microwave-assisted synthesis of selenium nanoparticles and their characterization under gastrointestinal conditions using mass spectrometry.

We present a novel microwave-assisted green synthesis of selenium nanoparticles (SeNPs) using yeast extract as source of a non-toxic reducing and capping agents. Effects of synthesis and gastrointestinal digestion conditions on the biogenic Se particle size distribution and number concentration using SP ICP MS were evaluated. The median equivalent diameter of SeNPs varied depending on the synthesis conditions. Upon incubation in simulated gastric juice, the increase of SeNPs size was observed, whereas after simulated intestinal juice addition, their size came back close to the initial value. The biomolecules contained in yeast extract, which play predominant role in the synthesis of SeNPs, were identified by non-targeted qualitative analysis using LC Orbitrap ESI MS. The use of the state-of-the-art MS techniques allowed both the comprehensive assessment of the processes leading to the SeNPs formation and the evaluation of their behavior under gastrointestinal conditions which is of utmost importance for their use as a novel selenium source.

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

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.

Calibration Strategy to Size and Localize Multi-Shaped Nanoparticles in Tissue Sections Using LA-spICP-MS.

In the field of nanotoxicology, the detection and size characterization of nanoparticles (NPs) in biological tissues become increasingly important. To gain information on both particle size and particle distribution in histological sections, laser ablation and single particle inductively coupled plasma-mass spectrometry (LA-spICP-MS) was used in combination with a liquid calibration of dissolved metal standards via a pneumatic nebulizer. In the first step, the particle size distribution of Ag NPs embedded in matrix-matched gelatine standards introduced via LA was compared with that of Ag NPs in a suspension and nebulizer-based ICP-MS. The data show that the particles remained intact by the ablation process as confirmed by transmission electron microscopy. Moreover, the optimized method was applied to CeO2 NPs that are highly relevant for (eco-)toxicological research but, unlike Ag NPs, are multi-shaped and have a broad particle size distribution. Upon analyzing the particle size distribution of CeO2 NPs in cryosections of rat spleen, CeO2 NPs were found to remain unchanged in size over 3 h, 3 d, and 3 weeks post-intratracheal instillation, with the fraction of smaller particles reaching the spleen first. Overall, LA-spICP-MS combined with a calibration based on dissolved metal standards is a powerful tool to simultaneously localize and size NPs in histological sections in the absence of particle standards.

Infrared Laser Desorption of Intact Nanoparticles for Digital Tissue Imaging.

We report a new technique for the digital mapping of biomarkers in tissues based on desorption and counting intact gold nanoparticle (Au NP) tags using infrared laser ablation single-particle inductively coupled plasma mass spectrometry (IR LA SP ICP MS). In contrast to conventional UV laser ablation, Au NPs are not disintegrated during the desorption process due to their low absorption at 2940 nm. A mass spectrometer detects up to 83% of Au NPs. The technique is demonstrated on mapping a proliferation marker, nuclear protein Ki-67, in three-dimensional (3D) aggregates of colorectal carcinoma cells, and the results are compared with confocal fluorescence microscopy and UV LA ICP MS. Precise counting of 20 nm Au NPs with a single-particle detection limit in each pixel by the new approach generates sharp distribution maps of a specific biomarker in the tissue. Advantageously, the desorption of Au NPs from regions outside the tissue is strongly suppressed. The developed methodology promises multiplex mapping of low-abundant biomarkers in numerous biological and medical applications using multielemental mass spectrometers.

Analysis of Ti- and Pb-based particles in the aqueous environment of Melbourne (Australia) via single particle ICP-MS

The analysis of natural and anthropogenic nanomaterials (NMs) in the environment is challenging and requires methods capable to identify and characterise structures on the nanoscale regarding particle number concentrations (PNCs), elemental composition, size, and mass distributions. In this study, we employed single particle inductively coupled plasma-mass spectrometry (SP ICP-MS) to investigate the occurrence of NMs in the Melbourne area (Australia) across 63 locations. Poisson statistics were used to discriminate between signals from nanoparticulate matter and ionic background. TiO2-based NMs were frequently detected and corresponding NM signals were calibated with an automated data processing platform. Additionally, a method utilising a larger mass bandpass was developed to screen for particulate high-mass elements. This procedure identified Pb-based NMs in various samples. The effects of different environmental matrices consisting of fresh, brackish, or seawater were mitigated with an aerosol dilution method reducing the introduction of salt into the plasma and avoiding signal drift. Signals from TiO2- and Pb-based NMs were counted, integrated, and subsequently calibrated to determine PNCs as well as mass and size distributions. PNCs, mean sizes, particulate masses, and ionic background levels were compared across different locations and environments.Graphical abstract

Characterisation of microplastics and unicellular algae in seawater by targeting carbon via single particle and single cell ICP-MS

The discharge of plastic waste and subsequent formation and global distribution of microplastics (MPs) has caused great concern and highlighted the need for dedicated methods to characterise MPs in complex environmental matrices like seawater. Single particle inductively coupled plasma – mass spectrometry (SP ICP-MS) is an elegant method for the rapid analysis of nano- and microparticles and to characterise number concentrations, mass, and size distributions. However, the analysis of carbon (C)-based microstructures such as MPs by SP ICP-MS is at an early stage. This paper investigates various strategies to improve figures of merit to detect and characterise MPs in complex matrices, such as seawater. Ten methods operating distinct acquisition modes with various collision/reaction gases, tandem MS (ICP-MS/MS) and targeting 12C or 13C were developed and compared for the analysis of polystyrene-based MPs standards in ultra-pure water and seawater. The robust analysis of MPs in seawater was accomplished by on-line aerosol dilution enabling repeatable size calibration while minimising drift effects. However, the direct analysis of seawater decreased ion transmission and required matrix-matching for accurate size calibration. Analysis of the 12C isotope instead of 13C improved the size detection limits (sDL) to 0.62 μm in ultra-pure water and to 0.96 μm in seawater. ICP-MS/MS methods decreased ion transmission but also reduced background signal and increased selectivity, particularly in the presence of spectral interferences. In the second part of this study, it was demonstrated that the developed methods were applicable for the analysis of C in unicellular organisms and allowed calibration of physical dimensions. This is relevant for the investigation and understanding of phenotypical traits associated, for example, with climate change resilience as well as oceanic C storage. SP/SC ICP-MS was employed to target five different intact Symbiodiniaceae algae strains with diverse life-histories in seawater and polystyrene-based MPs were used to calibrate cellular C masses, which were between 51 and 83 pg. The C mass distribution across the analysed unicellular cells was used for modelling cell sizes, which were in the range of 7.6 and 10.1 μm. Determined values were in line with values obtained with complementary techniques (Coulter-counting, total organic C analysis and microscopic analysis).

Characterization of Upconversion Nanoparticles by Single-Particle ICP-MS Employing a Quadrupole Mass Filter with Increased Bandpass.

This work introduces new methods to characterize dispersions of small-diameter or low-mass-fraction nanoparticles (NPs) by single-particle inductively coupled plasma-mass spectrometry (SP ICP-MS). The optimization of ion extraction, ion transport, and the operation of the quadrupole with increased mass bandwidth improved the signal-to-noise ratios significantly and decreased the size detection limits for all NP dispersions investigated. As a model system, 10.9 ± 1.0 nm Au NPs were analyzed to demonstrate the effects of increasing ion transmission. Specifically, increasing the mass bandwidth of the quadrupole improved the size detection limit to 4.2 nm and enabled the resolution of NP signals from ionic background and noise. Subsequently, the methods were applied to the characterization of lanthanide-doped upconversion nanoparticles (UCNPs) by SP ICP-MS. Three different types of UCNPs (90 nm NaYF4: 20% Yb, 2% Er; 20 nm NaGdF4: 20% Yb, 1% Er; 15nm NaYF4: 20% Yb, 2% Er) were investigated. Y showed the best signal-to-noise ratios with optimized ion extraction and transport parameters only, whereas the signal-to-noise ratios of Gd, Er, and Yb were further improved by increasing the mass bandwidth of a quadrupole mass filter. The novel methods were suitable for detailed characterization of diluted UCNP dispersions including particle stoichiometries and size distributions. A Poisson model was further applied to assess particle-particle interactions in the aqueous dispersions. The methods have considerable potential for the characterization of small-diameter and/or low-mass-fraction nanoparticles.

ICP-MS based methods to characterize nanoparticles of TiO2 and ZnO in sunscreens with focus on regulatory and safety issues

This study sought to develop analytical methods to characterize titanium dioxide (TiO2) and zinc oxide (ZnO) nanoparticles (NPs), including the particle size distribution and concentration, in cream and spray sunscreens with different sun protection factor (SPF). The Single Particle Inductively Coupled Plasma-Mass Spectrometry (SP ICP-MS) was used as screening and fast method to determine particles size and number. The Asymmetric Flow-Field Flow Fractionation (AF4-FFF) as a pre-separation technique was on-line coupled to the Multi-Angle Light Scattering (MALS) and ICP-MS to determine particle size distributions and size dependent multi-elemental concentration. Both methods were optimized in sunscreens in terms of recovery, repeatability, limit of detection and linear dynamic range. Results showed that sunscreens contained TiO2 particles with an average size of ≤107 nm and also a minor number of ZnO particles sized ≤98 nm. The higher fraction of particles <100 nm was observed in sunscreens with SPF 50+ (ca. 80%); the lower percentage (12–35%) in sunscreens with lower SPF values. Also the higher TiO2 (up to 24% weight) and ZnO (ca. 0.25% weight) concentrations were found in formulations of SPF 50+. Creamy sunscreens could be considered safe containing TiO2 and ZnO NPs less than the maximum allowable concentration of 25% weight as set by the European legislation. On the contrary, spray products required additional considerations with regard to the potential inhalation of NPs. The developed methods can contribute to the actual demand for regulatory control and safety assessment of metallic NPs in consumers' products.

Characterization of Dissolved Metals and Metallic Nanoparticles in Asphaltene Solutions by Single-Particle Inductively Coupled Plasma Mass Spectrometry

Even though evaluating the metal content in asphaltenes is now a routine analysis, determining the nature of the metals present in asphaltenes has continued to be an elusive subject. In this work, we presented, for the first time, the application of single-particle inductively coupled plasma mass spectrometry (spICP–MS) in hydrocarbon media to determine the presence of metal-containing nanoparticles in asphaltene solutions. This method also offers the unique ability to differentiate between metal-containing nanoparticles and dissolved metals. The study of three asphaltene samples from different origins indicates that vanadium and nickel are entirely dissolved probably as part of soluble coordination complexes, such as porphyrins. In clear contrast, we found that molybdenum and iron are forming part of nanoparticles and report nanoparticle distributions. We found that nanoparticle distributions for molybdenum are very similar for the different asphaltenes, while for iron oxide, the size increases as the co...

Identification of platinum nanoparticles in road dust leachate by single particle inductively coupled plasma-mass spectrometry

Elevated platinum (Pt) concentrations are found in road dust as a result of emissions from catalytic converters in vehicles. This study investigates the occurrence of Pt in road dust collected in Ghent (Belgium) and Gothenburg (Sweden). Total Pt contents, determined by tandem ICP-mass spectrometry (ICP-MS/MS), were in the range of 5 to 79ngg−1, comparable to the Pt content in road dust of other medium-sized cities. Further sample characterization was performed by single particle (sp) ICP-MS following an ultrasonic extraction procedure using stormwater runoff for leaching. The method was found to be suitable for the characterization of Pt nanoparticles in road dust leachates. The extraction was optimized using road dust reference material BCR-723, for which an extraction efficiency of 2.7% was obtained by applying 144kJ of ultrasonic energy. Using this method, between 0.2% and 18% of the Pt present was extracted from road dust samples. spICP-MS analysis revealed that Pt in the leachate is entirely present as nanoparticles of sizes between 9 and 21nm. Although representing only a minor fraction of the total content in road dust, the nanoparticulate Pt leachate is most susceptible to biological uptake and hence most relevant in terms of bioavailability.

Rapid analysis of titanium dioxide nanoparticles in sunscreens using single particle inductively coupled plasma–mass spectrometry

Titanium dioxide (TiO2) particles in the nanometer (nm) size range are widely used in commercial sunscreens. Single particle inductively coupled plasma–mass spectrometry (SP-ICP–MS) is an emerging methodology for nanoparticle (NP) characterization and quantification. In this study, a rapid SP-ICP–MS method was developed to simultaneously determine the primary particle size, size distribution, particle concentration (particles/mL), and mass content (weight percent) of TiO2 NPs in commercial sunscreens. Quality control data indicated that the developed method was capable of accurately measuring TiO2 particle size in sunscreen matrix. Four types of commercial sunscreens containing different amounts of TiO2 were analyzed, and the primary particle sizes detected varied from 32nm to 40nm in the different sunscreens tested. TiO2 existed as TiO2 particles in the tested sunscreens. The TiO2 mass contents in these sunscreens were also determined by a novel standard addition-SP-ICP–MS method, using a 40nm TiO2 NP as the NP standard. Although the measured TiO2 mass content was close to that determined by acid digestion and the manufacturer-claimed content, improvement in accuracy is needed and can be achieved if better-matched NP standards available. The standard addition-SP-ICP–MS method offers a promising alternative for determining the TiO2 NP mass content in sunscreen, in lieu of using the laborious, time-consuming, and costly acid digestion-ICP–MS method. The major advantages of SP-ICP–MS analysis are easy sample preparation, high throughput, and informative results (particle size information and total TiO2 mass content).

Multimethod quantification of Ag+ release from nanosilver

There is a significant interest in determining the effects of nanomaterials on the environment and human health. Part or all of the toxicity attributed to silver nanoparticles (nAg) may be due to the release of free silver (Ag+). Therefore, it is necessary to have techniques that will allow the precise determination of free Ag+ within suspensions of nAg particles. Among the different methods used for the determination of free metals in natural waters, the ion-exchange technique (IET), has promise to both distinguish Ag+ from nAg and to attain the low detection limits required for the analysis of natural samples. In this paper, IET. centrifugal ultrafiltration and single particle inductively coupled plasma mass spectrometry (SP ICP-MS) were used to determine very low concentrations of free or dissolved Ag in commercial suspensions of nAg. Dilution of the silver nanoparticles played an important role in the measured Ag+ concentrations. The relative release of Ag+ from nAg increased as samples were increasingly diluted, implying that it is critical to determine Ag+ concentrations under the precise conditions used for determinations of toxicological or environmental fate.