| 1. |
- Cornelis, Geert, et al.
(author)
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Challenges and current approaches toward environmental monitoring of nanomaterials
- 2021
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In: Monitoring Environmental Contaminants : A volume in Environmental Contaminants. - 9780444643360 ; , s. 73-108
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Book chapter (peer-reviewed)abstract
- Engineered nanomaterials (ENMs), i.e., man-made particles having at least one dimension smaller than 100nm, have found their way into the environment. Parallel to the efforts to elucidate the possible harmful effects of ENMs, techniques have been developed to monitor environmental ENM concentrations. This chapter discusses the techniques that can currently distinguish ENMs from naturally occurring particles at realistic concentration detection limits without a tedious sample pretreatment procedure. For inorganic ENMs, the most promising approach is based on single particle ICP-MS, and this technique has been developed in recent years to measure solid samples in addition to aquatic samples and distinguish the many different forms of occurrence of ENMs in realistic samples from naturally occurring particles. The detection capabilities for C-based particles are lagging and will likely be the focus of analytical developments in the coming years.
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| 2. |
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| 3. |
- Farkas, Julia, et al.
(author)
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Characterization of the effluent from a nanosilver producing washing machine
- 2011
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In: Environment International. - : Elsevier BV. - 0160-4120 .- 1873-6750. ; 37:6, s. 1057-1062
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Journal article (peer-reviewed)abstract
- The increasing number of nanomaterial based consumer products raises concerns about their possible impact on the environment. This study provides an assessment of the effluent from a commercially available silver nanowashing machine. The washing machine released silver in its effluent at an average concentration of 11 mu g L(-1), as determined by inductive coupled mass spectrometry (ICP-MS). The presence of silver nanoparticles (AgNPs) was confirmed by single particle ICP-MS as well as ion selective electrode measurements and filtration techniques. Size measurements showed particles to be in the defined nanosize range, with an average size of 10 nm measured with transmission electron microscopy (TEM) and 60-100 nm determined with nanoparticle tracking analysis (NTA). The effluent was shown to have negative effects on a natural bacterial community as its abundance was clearly reduced when exposed to the nanowash water. If washing machines capable of producing AgNPs become a common feature of households in the future, wastewater will contain significant loadings of AgNPs which might be released into the environment.
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| 4. |
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| 5. |
- Gallego-Urrea, Julian A., 1977, et al.
(author)
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Measurements of nanoparticle number concentrations and size distributions in contrasting aquatic environments using nanoparticle tracking analysis
- 2010
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In: Environmental Chemistry. - 1449-8979. ; 7, s. 67-81
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Journal article (peer-reviewed)abstract
- A feasibility study of nanoparticle tracking analysis (NTA) for aquatic environmental samples is presented here. The method has certain virtues such as minimum perturbation of the samples, high sensitivity in terms of particle concentration, and provision of number-based size distributions for aquatic samples. NTA gave linear calibration curves in terms of number concentration and accurately reproduced size measurements of certified reference material nanoparticles. However, the accuracy of the size distributions obtained with this method exhibited a high dependence on set-up parameters and the concentrations were shown to be strongly correlated with the refractive index of the material under examination. Different detection cameras and different data acquisition modeswere compared and evaluated. Also, the effect of filtration of the samples was assessed. The size distributions for the contrasting environmental samples were fairly reasonable compared with other studies but an underestimation of small sizes was observed, which can be explained by a materialdependent lower detection limit in terms of size. The number concentrations obtained for the natural nanoparticles ranged from 0.5 to 20×108 particles mL−1 and correlated well with conventional turbidity measurements.
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| 6. |
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| 7. |
- Ma, Su, et al.
(author)
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Direct Electron-Transfer Anisotropy of a Site-Specifically Immobilized Cellobiose Dehydrogenase
- 2019
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In: ACS Catalysis. - : American Chemical Society (ACS). - 2155-5435. ; , s. 7607-7615
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Journal article (peer-reviewed)abstract
- To study the direct electron transfer (DET) of the multicofactor enzyme cellobiose dehydrogenase (CDH) in regard to its orientation on an electrode surface, a recently published, maleimide-based immobilization method was used in combination with site-directed mutagenesis to establish different orientations on an electrode surface. CDH from Myriococcum thermophilum was chosen for this study because its protein structure is resolved and the factors influencing the movement of its mobile cytochrome domain (CYT) are established. Seven CDH variants with a surface-exposed cysteine residue in different spatial positions were generated for site-specific maleimide coupling. Surface plasmon resonance and cyclic voltammetry showed that all CDH variants, but not the wild-type CDH, bound covalently to gold electrodes or glassy carbon electrodes and were catalytically active. For DET, the CYT domain needs to move from the closed-state conformation, where it obtains an electron from the catalytic flavin adenine dinucleotide (FAD) cofactor to the open state where it can donate an electron to the electrode. We therefore hypothesized that the mobility of the CYT domain and its distance to the electrode is central for DET. We found that the uniform spatial orientations of CDH influenced DET as follows: an orientation of the two-domain enzyme on the side, with CYT in proximity to the electrode, resulted in high DET currents. Orientations with a bigger distance between CYT and the electrode, or orientations where CYT could not swing back to the dehydrogenase domain to form the closed enzyme conformation, reduced DET. In the latter case, calcium ions that stabilize the closed conformation of CDH fully recovered DET. The study demonstrates that a mobile CYT domain can compensate unfavorable orientations of the catalytic domain to a great extent and allows CDH as a multicofactor enzyme to transfer electrons even in awkward orientations. The mobile CYT domain reduces the anisotropy of DET, which is also essential for CDH's physiological function as an extracellular, electron-transferring enzyme.
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| 8. |
- Minelli, Caterina, et al.
(author)
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Versailles project on advanced materials and standards (VAMAS) interlaboratory study on measuring the number concentration of colloidal gold nanoparticles
- 2022
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In: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3372 .- 2040-3364. ; 14, s. 4690-4704
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Journal article (peer-reviewed)abstract
- We describe the outcome of a large international interlaboratory study of the measurement of particle number concentration of colloidal nanoparticles, project 10 of the technical working area 34, "Nanoparticle Populations" of the Versailles Project on Advanced Materials and Standards (VAMAS). A total of 50 laboratories delivered results for the number concentration of 30 nm gold colloidal nanoparticles measured using particle tracking analysis (PTA), single particle inductively coupled plasma mass spectrometry (spICP-MS), ultraviolet-visible (UV-Vis) light spectroscopy, centrifugal liquid sedimentation (CLS) and small angle X-ray scattering (SAXS). The study provides quantitative data to evaluate the repeatability of these methods and their reproducibility in the measurement of number concentration of model nanoparticle systems following a common measurement protocol. We find that the population-averaging methods of SAXS, CLS and UV-Vis have high measurement repeatability and reproducibility, with between-labs variability of 2.6%, 11% and 1.4% respectively. However, results may be significantly biased for reasons including inaccurate material properties whose values are used to compute the number concentration. Particle-counting method results are less reproducibile than population-averaging methods, with measured between-labs variability of 68% and 46% for PTA and spICP-MS respectively. This study provides the stakeholder community with important comparative data to underpin measurement reproducibility and method validation for number concentration of nanoparticles.
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| 9. |
- Moreira, Beatriz, et al.
(author)
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Surface Plasmon Resonance for Measuring Exocytosis from Populations of PC12 Cells: Mechanisms of Signal Formation and Assessment of Analytical Capabilities
- 2017
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In: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 89:5, s. 3069-3077
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Journal article (peer-reviewed)abstract
- Because of cell to cell variation, it is difficult to obtain statistically significant data on the frequency of exocytosis events (R-exocytosis, t(-1) m(-2)) with traditional single cell electrophysiological or fluorescence microscopy based methods. Here we take the first steps toward a rapid cost-effective surface plasmon resonance (SPR) based method for measuring the R-exocytosis for populations of PC12 cells. The conditions for culturing confluent monolayers on the sensor slides were optimized, and neurotransmitter exocytosis was evoked by injecting solutions with elevated Exocytosis caused a shift of the resonance angle (Delta theta(r)) that was linearly proportional to R-exocytosis The Delta theta(r) was mainly due to elevated concentration of secretory vesicles close to the cell membrane. The increased vesicle concentration thus acted as a proxy for the Rexocytosis that could not be measured directly. The Delta theta(r) was calibrated for it R-exocytosis using single cell amperometry on parallel cell cultures. The cell populations were large enough for variation in responses between sensor slides to only reflect actual differences in biological condition. The applicability for drug screening is demonstrated by studying the effects of EGTA, reserpine, and prolonged stimulation by K+
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| 10. |
- Tuoriniemi, Jani, 1982, et al.
(author)
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A new peak recognition algorithm for detection of ultra-small nano-particles by single particle ICP-MS using rapid time resolved data acquisition on a sector-field mass spectrometer
- 2015
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In: Journal of Analytical Atomic Spectrometry. - : Royal Society of Chemistry (RSC). - 0267-9477 .- 1364-5544. ; 30:8, s. 1723-1729
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Journal article (peer-reviewed)abstract
- The applicability of single particle inductively coupled plasma mass spectrometry (spICPMS) is currently limited to particles larger than similar to 10 nm in diameter. In this work, the size detection limit (DLs) was improved by resolving the ion bursts originating from silver or gold nanoparticles (AgNPs or AuNPs) using real time data acquisition with 0.1 ms time resolution. Such acquisition is here called the Fast Acquisition Speed Technique (FAST). The analytical capabilities of the FAST were evaluated on a sector field instrument with high ion transmission efficiency (ITE). An algorithm for distinguishing particle events from dissolved and/or background signals was developed, and it was possible to detect 6.4 nm AuNPs that delivered only 2 ions to the detector. The influence of dwell time was investigated and it was concluded that the minimum DLs is achieved for dwell times close to the duration of particle events similar to 0.2 ms. Attempts to further improve the DLs should therefore be focused on increasing the ITE of the mass spectrometer.
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| 11. |
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| 12. |
- Tuoriniemi, Jani, 1982, et al.
(author)
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Determination of the Distance Between the Cytochrome and Dehydrogenase Domains of Immobilized Cellobiose Dehydrogenase by Using Surface Plasmon Resonance with a Center of Mass Based Model
- 2020
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In: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 92:3, s. 2620-2627
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Journal article (peer-reviewed)abstract
- Changes in the tertiary conformation of adsorbed biomolecules can induce detectable shifts (Delta theta(r)) in the surface plasmon resonance (SPR) angle. Here it is shown how to calculate the corresponding shifts in the adsorbate's center of mass (Delta z(avg)) along the sensing surface normal from the measured Delta theta(r). The novel developed model was used for determining the mean distance between the cytochrome (CYT) and flavodehydrogenase (DH) domains of the enzyme cellobiose dehydrogenase (CDH) isolated from the fungi Neurospora crassa, Corynascus thermophilus, and Myriococcum thermophilum as a function of pH, [Ca2+], and substrate concentration. SPR confirmed the results from earlier electrochemical and SAXS studies stating that the closed conformation, where the two domains are in close vicinity, is stabilized by a lower pH and an increased [Ca2+]. Interestingly, an increasing substrate concentration in the absence of any electron acceptors stabilizes the open conformation as the electrostatic repulsion due to the reaped electrons pushes the DH and CYT domains apart. The accuracy of distance determination was limited mostly by the random fluctuations between replicate measurements, and it was possible to detect movements <1 nm of the domains with respect to each other. The results agreed with calculations using already established models treating conformational changes as contraction or expansion of the thickness of the adsorbate layer (t(protein)). Although the models yielded equivalent results, in this case, the Delta z(avg)-based method also works in situations, where the adsorbate's mass is not evenly distributed within the layer.
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| 13. |
- Tuoriniemi, Jani, 1982, et al.
(author)
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Determining Number Concentrations and Diameters of Polystyrene Particles by Measuring the Effective Refractive Index of Colloids Using Surface Plasmon Resonance
- 2016
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In: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 32:41, s. 10632-10640
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Journal article (peer-reviewed)abstract
- The capabilities of surface plasmon resonance (SPR) for characterization of colloidal particles were evaluated for 100, 300, and 460 nm nominal diameter polystyrene (PS) latexes. First the accuracy of measuring the effective refractive index (n(eff)) of turbid colloids using SPR was quantified. It was concluded that for submicrometer sized PS particles the accuracy is limited by the reproducibility between replicate injections of samples. An SPR method was developed for obtaining the particle mean diameter (d(part)) and the particle number concentration (c(p)) by fitting the measured n(eff) of polystyrene (PS) colloids diluted in series with theoretical values calculated using the coherent scattering theory (CST). The d(part) and c(p) determined using SPR agreed with reference values obtained from size distributions measured by scanning electron microscopy (SEM), and the mass concentrations stated by the manufacturer. The 100 nm particles adsorbed on the sensing surface, which hampered the analysis. Once the adsorption problem has been overcome, the developed SPR method has potential to become a versatile tool for characterization of colloidal particles. In particular, SPR could form the basis of rapid and accurate methods for measuring the c(p) of submicrometer particles in dispersion.
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| 14. |
- Tuoriniemi, Jani, 1982, et al.
(author)
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Improving the accuracy of single particle ICPMS for measurement of size distributions and number concentrations of nanoparticles by determining analyte partitioning during nebulisation
- 2014
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In: Journal of Analytical Atomic Spectrometry. - : Royal Society of Chemistry (RSC). - 0267-9477 .- 1364-5544. ; 29:4, s. 743-752
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Journal article (peer-reviewed)abstract
- Application of single particle ICP-MS (spICPMS) for measurement of the size and number concentration, c(p), of nanoparticles is currently hampered by insufficient accuracy. The relative contributions of different types of noise to the overall uncertainty during spICPMS measurements of Ag and Au nanoparticle dispersions were quantified showing that the accuracy of spICPMS is mainly limited by the uncertainty in nebulization efficiency (f(neb)). This uncertainty was improved by correcting f(neb) for analyte partitioning effects during nebulization, and the calculated Ag and Au nanoparticle sizes were in close agreement with sizes determined by scanning electron microscopy. The duration of the particle events was measured, which allowed correction for incomplete particle events and detector dead time, and determination of the effective dwell time for particle counting. The c(p) measured with spICPMS agreed with that measured by counting particles deposited on filters, and calculated from the mass concentration of the analyte.
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| 15. |
- Tuoriniemi, Jani, 1982, et al.
(author)
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In situ characterisation of physicochemical state and concentration of nanoparticles in soil ecotoxicity studies using environmental scanning electron microscopy
- 2014
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In: Environmental Chemistry. - : CSIRO Publishing. - 1448-2517. ; 11:4, s. 367-376
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Journal article (peer-reviewed)abstract
- The interpretation of nanoparticle toxicity data in soils is currently impeded by the lack of methods capable of characterising particles in situ. To draw relevant and accurate conclusions it would be desirable to characterise particle sizes, agglomeration state and number concentrations. In this article, methodologies for imaging nanoparticles in soils are evaluated for conventional scanning electron microscopy (SEM) and environmental or variable pressure scanning electron microscopy (ESEM). A protocol for dispersing Au particles (similar to 25 to similar to 450 nm) into soil without causing aggregation was developed. The number of particles observed per imaged area of soil correlated linearly with concentration. To determine the number of particles per volume of soil it was also necessary to know how deep in the sample the particles can be visualised. The depth was estimated by both using the Kanaya Okayama model, and spiking the soil with dispersions of known number concentration. These concentrations were determined with a range of methods to ensure their accuracy. Because larger particles can be detected deeper in the matrix, such a calibration should be performed over a range of particle sizes.
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| 16. |
- Tuoriniemi, Jani, 1982, et al.
(author)
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Intermethod comparison of the particle size distributions of colloidal silica nanoparticles
- 2014
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In: Science and Technology of Advanced Materials. - : Informa UK Limited. - 1468-6996 .- 1878-5514. ; 15:3
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Journal article (peer-reviewed)abstract
- There can be a large variation in the measured diameter of nanoparticles depending on which method is used. In this work, we have strived to accurately determine the mean particle diameter of 3040 nm colloidal silica particles by using six different techniques. A quantitative agreement between the particle size distributions was obtained by scanning electron microscopy (SEM), and electrospray-scanning mobility particle sizer (ES SMPS). However, transmission electron microscopy gave a distribution shifted to smaller sizes. After confirming that the magnification calibration was consistent, this was attributed to sample preparation artifacts. The hydrodynamic diameter, d(h), was determined by dynamic light scattering (DLS) both in batch mode, and hyphenated with sedimentation field flow fractionation. Surprisingly the dh were smaller than the SEM, and ES SMPS diameters. A plausible explanation for the smaller sizes found with DLS is that a permeable gel layer forms on the particle surface. Results from nanoparticle tracking analysis were strongly biased towards larger diameters, most likely because the silica particles provide low refractive index contrast. Calculations confirmed that the sensitivity is, depending on the shape of the laser beam, strongly size dependent for particles with diameters close to the visualization limit.
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| 17. |
- Tuoriniemi, Jani, et al.
(author)
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Measurement of number concentrations and sizes of Au nano-particles spiked into soil by laser ablation single particle ICPMS
- 2020
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In: Journal of Analytical Atomic Spectrometry. - : Royal Society of Chemistry (RSC). - 0267-9477 .- 1364-5544. ; 35, s. 1678-1686
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Journal article (peer-reviewed)abstract
- A novel method to directly quantify nanoparticles (NPs) in a soil matrix by laser ablation single particle inductively coupled plasma mass spectrometry (LA-sp-ICPMS) was developed. Different concentrations of 60, 100, or 250 nm diameter gold NPs (AuNP) were deposited directly on polyether sulfone (PES) ultrafiltration membranes or immersed in soil. The ICPMS sensitivity was calibrated using aqueous dissolved Au standards and an aqueous AuNP size standard dispersion was used to calculate the transmission efficiency. In the case of the soil samples, sizing proved to be more accurate when calibration occurred while ablating a non-spiked soil. A linear relation was found between the spiked AuNP number concentrations and the particle event frequencies measured in the ablated area. Particle recovery on PES filters ranged only between 29 to 42% and recovery of soil-spiked AuNP on thin tape was between 15 and 60% and increased with size. However, 70-85% mass recovery in the ablated area was obtained when the soil sample was deposited on a thicker, opaque double sided tape suggesting that the substrate material is instrumental in absorbing excess laser energy thus enhancing recovery. The rate of soil ablation and mass transfer into the plasma was quantified to calculate the recovery using the same soils spiked with indium. The presented method thus has significant potential to be used for routine quantification of the particle size distributions of engineered or natural NPs in soil and possibly other powder samples with significantly fewer artifacts than extraction followed by aqueous analysis.
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| 18. |
- Tuoriniemi, Jani, 1982
(author)
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New single particle methods for detection and characterization of nanoparticles in environmental samples
- 2013
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Doctoral thesis (other academic/artistic)abstract
- Nanoparticles (NP) are being used in rapidly increasing quantities which has resulted in concerns about possible harmful effects for health and environment. NP are already undergoing similar risk assessment programs as conventional chemicals, and due to their enhanced surface reactivities it has been proposed that the use of NP should be regulated by specific legislation based on particle size. Number based concentrations and size distributions are thought to be more relevant dose metrics for toxicology than the mass of NP. Because NP are prone to processes such as aggregation, dissolution, or adsorption on surfaces characterization is required during the whole test. To measure the emission of NP and exposure levels in the environment the methods have to be capable of quantifying and sizing particles of interest at parts per billion level concentrations or lower. Nanoparticle tracking analysis (NTA) was evaluated for measurement of number concentration and size distributions. The technique was considered suitable for monitoring and measuring exposure at relatively high (> 106 particles mL-1) concentrations; however, NTA is relatively unspecific in the sense that it is difficult to distinguish particles of different materials. To increase sensitivity and specificity single particle inductively coupled plasma mass spectrometry (spICP-MS) was developed for element specific characterization of particles in liquid samples. Validation of both the number concentration and sizing capabilities was carried out at concentrations as low as 102 particles mL-1.The capabilities of spICP-MS as a fast screening tool for NP was evaluated, and the method was used to quantify trace level contamination of WC particles emitted from wear of winter tire studs and hard coatings. Variable pressure or environmental scanning electron microscopes (ESEM) can be applied on a waist range of sample types with no or very little sample preparation. Therefore backscattered electron (BSE) imaging in such instrument was chosen as a base for developing a method for quantification of particles in solid samples. The technique was applied for quantifying particles in toxicity tests involving soil biota, and was concluded to be sensitive enough to cover the concentration range that is typically of interest in such tests. Finally it was concluded that due to the tremendous amount of information obtained on a single particle basis, electron microscopy is a suitable complementing technique for spICP-MS measurements, which otherwise give little information about the structure of the particles.
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| 19. |
- Tuoriniemi, Jani, 1982, et al.
(author)
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Size dependence of silver nanoparticle removal in a wastewater treatment plant mesocosm measured by FAST single particle ICP-MS
- 2017
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In: Environmental Science-Nano. - : Royal Society of Chemistry (RSC). - 2051-8153 .- 2051-8161. ; 4:5, s. 1189-1197
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Journal article (peer-reviewed)abstract
- The quantities of engineered nanoparticles (NP) released to the environment are often influenced by their fate in waste water treatment plants (WWTP). Here, 40 nm silver NP (AgNP) were spiked into a mesocosm simulating the process used at a major municipal WWTP. The evolution of the mass distributions and number concentrations were followed by fast acquisition speed technique single particle inductively coupled mass spectrometry (FAST spICP-MS) using a high-resolution ICP-MS. It was thus possible to detect smaller Ag containing NP than hitherto possible in similar studies. These small particles (ca. 5-10 nm in corresponding metallic Ag equivalent spherical diameter) were possibly dissolved Ag+ precipitated as Ag2S particles. They were detected immediately upon spiking and were stable with respect to aggregation and thus much less removed by the WWTP process compared to the 40 nm AgNP. The results also suggested that any transformation of the latter AgNP occurred without dissolution. Most of these larger AgNP were probably removed by aggregation with large floc particles and subsequent sedimentation with the suspended particulate matter in the simulated WWTP process. The results have implications for differentiating the fate of nanoparticles as a function of size and demonstrate how spICP-MS can reveal such size-dependent fate dynamics.
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| 20. |
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