Search

This work has focused on the development of a new analytical alternative based on the laser-induced breakdown spectroscopy (LIBS) technique for the fast, reliable, and economical determination of the gold and silver nanoparticle content in a low linear concentration range between 2.9 and 0.058 μg mL−1 and 2.9–0.116 μg mL−1, respectively, without requiring complicated sample pretreatment procedures or advanced separation techniques. Metallic nanoparticles are currently essential materials for the development of new technologies in different scientific and technical areas. However, numerous studies have pointed out these nanomaterials' toxic and polluting potential and the various health implications for humans, animals, and the ecosystem. The current reality reflects the lack of analytical techniques with low economic, environmental, and health impacts and the capacity to quantify the total metallic nanoparticle content. For this purpose, a novel and simple method for the selective capture of gold and silver nanoparticles, consisting of a chemically functionalized glass surface, has been custom-developed for subsequent analysis with LIBS. The results show that the proposed method, employing a functionalized sample glass support, presents a suitable analytical performance characterized by increased sensitivity, specifically 4.7% and 329.2% for Au-NPs and Ag-NPs, and proportionally decreased error in the slope and intercept of the calibration curves, 68% for Au-NPs and 87% for Ag-NPs, respectively. [ABSTRACT FROM AUTHOR]

Single-cell analysis using inductively coupled plasma mass spectrometry (SC-ICP-MS) is an analytical methodology that allows to obtain qualitative and quantitative information of the element content of bioparticles (cells, bacteria, unicellular algae, yeasts...) on a cell-by-cell basis. In this study, two commercially available nebulisation systems for introduction of intact bioparticles were evaluated, showing similar performance. Bacteria (E. coli) exposed to Ag(I) and 10 nm Ag nanoparticles were detected and their complete silver content distributions successfully recorded. Analysis of the corresponding spheroplasts, obtained after enzymatic digestion of the bacterial outer membrane with lysozyme, allowed information about the intracellular silver to be obtained, providing an insight into the biodistribution of silver in the bacteria. Likewise, validity of the quantitative information obtained by SC-ICP-MS was evaluated by applying methodology based on the estimation of silver mass per bioparticle critical values and successive dilutions. The quantitative information obtained by SC-ICP-MS for the total content of silver in bacteria and spheroplasts was confirmed by acid digestion followed by conventional ICP-MS analysis. Bacteria exposed to silver nanoparticles accumulated lower amounts of silver than those exposed to ionic silver, the latter being totally internalized, showing the higher bioavailability of ionic silver. This study proves for the first time the suitability of SC-ICP-MS for the quantitative determination of silver in bacteria, as well as in spheroplasts when combined with lysozyme digestion. Limits of detection of 7 ag of Ag per bioparticle, 500 bioparticles per mL and 38 ng of total Ag per litre of bacteria/spheroplast suspension were achieved. [ABSTRACT FROM AUTHOR]

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is a method with high potential to visualize the distribution of elements in different samples, including a variety of organisms. This study aimed to demonstrate the broad application of LA-ICP-MS in nanomaterial-biota fate studies as a high throughput bioimaging tool and to broaden the choice of standard organism models in material-biota interaction research. In this study, operation parameters of LA-ICP-MS were optimised on one organism, woodlice Porcellio scaber. Subsequently, the scanning conditions were tested on a range of aquatic (Girardia tigrina, Lumbriculus variegatus, and Oncorhynchus mykiss), terrestrial organisms (Lumbricus rubellus, Porcellio scaber) and one plant (Triticum aestivum) upon exposure to Ag2S nanoparticles (NPs) and silver nitrate (AgNO3). Model organisms were exposed in aquatic or terrestrial mesocosm experiments where nominal concentrations of Ag were 10 μg Ag per L of water and 10 mg Ag per kg of soil, respectively. The results showed that both sample preparation and LA-ICP-MS imaging conditions, as optimized on the selected organism (65 μm laser diameter, scan rate 100 μm s−1, measuring duration 35 min), are applicable on different tissues. These LA-ICP-MS imaging conditions enable recognition of the main biological structures and biodistribution of elements of interest. By using fast-screening LA-ICP-MS, we confirmed the presence of Ag2S NPs on the body surface or in the gut lumen (adsorbed and retained), but not in other internal parts of organisms, which is consistent with our previous toxicokinetic studies. The presence of Ag was also confirmed in some parts of wheat roots. The advantage of this technique is the possibility of sequential use of fast- and slow-scanning steps to optimise the duration of analysis and data processing, whilst also improving cost-effectiveness without compromising the quality of results. [ABSTRACT FROM AUTHOR]

The factors influencing the signal noise and its contribution to the uncertainty of a single AgNP size in spICP-MS were investigated. The possibility of the reproducible delivery of Ag masses (0.045–5.4 fg) corresponding to nanoparticles with pre-selected diameters (20–100 nm) by time segmentation when introducing homogeneous ionic standards is experimentally proven. The calculation of ionic standard concentration ensuring the delivery of desired Ag mass within a certain dwell time (td) and the dilution factor of nanocolloid samples was done by the developed theoretical model. The behavior of the time-segmented signals was studied for five different Ag masses measured within four td in the interval of 3–10 ms. The results show that both the sensitivity and the reproducibility of the signals are independent of the selected td. The hypothesis of dispersion homogeneity was verified by Bartlett's test and in all cases, the calculated values of the Bartlett criterion (Bexp) were much lower than Bcrit, which prove that signal noise depends only on the Ag mass and can be used as a reliable estimate of the contribution of ionization in plasma and ion flux transport to uncertainty. The correspondence of both calibrations by ionic standards and AgNPs RM confirm that the signals are comparable, regardless of whether Ag is introduced via ionic solutions or directly as nanoparticles. The combined uncertainty (RSDc%) was calculated for Ag masses consistent to the size of nanoparticles, and the contribution of different quantities was evaluated. The AgNPs' diameter confidence intervals (1σ, P = 68%) were calculated. Two main trends were observed: (i) with decreasing size, Uc increased and (ii) due to the cubic relationship between the mass and diameter of NPs, the two half-intervals became asymmetric. The approach was used for the calculation of the size Uc of AgCl, AgI, Ag2O, and Ag2S nanoparticles, which are of ecological interest, but no reference materials are available. The average uncertainty interval depends on the physical properties of the nanoparticles and varies between 3.4 nm and 5.5 nm for Ag and AgI, respectively. This allows the experimental evaluation of the spICP-MS size resolution and to propose a criterion for the cluster dimension when size distribution is obtained. The method was applied for the analysis of AgNPs in a commercial pharmaceutical product. The suggested approach for calculating the uncertainty in the diameters is flexible and can be applied to different types of nanoparticles. [ABSTRACT FROM AUTHOR]

Interactions of silver(I) and PVP-stabilized silver nanoparticles (AgNPs) of different nominal diameters (40, 60 and 75 nm) with green microalgae Desmodesmus subspicatus during a 24 h incubation period in matrices that mimic surface water and natural river water were studied by single particle inductively coupled plasma mass spectrometry (spICP-MS). It was found that the uptake of silver species by algae was dependent on the type of matrix and was the lowest in ultrapure water and the highest in the presence of high concentrations of inorganic cations. AgNP uptake was size dependent and decreased with increasing particle size. Higher stability of AgNPs was observed in the presence of organic compounds, for both surface water and green algae origin. Three procedures of AgNP extraction from algal cells were tested: direct extraction, extraction by enzymatic digestion with pectinase (Macerozyme R-10) and by alkaline digestion with tetramethylammonium hydroxide (TMAH). In order to identify the source of overestimation of the results obtained in samples rich in organic matrix, interference studies were carried out. Two matrix-matched variants of calibration (using digestion reagents with or without cell lysates) for both AgNPs and Ag+ were tested for different extraction procedures. The silver recovery and AgNP size determined after enzymatic digestion of algal cells were highly dependent on the type of calibration used showing the occurrence of non-spectral interferences. Extraction of AgNPs using the alkaline digestion procedure (10% TMAH, 24 h, room temperature) and calibration using 0.1% TMAH + 0.1% Triton X-100 was found to give accurate results in terms of both the recovery and size of AgNPs. The developed procedure was applied to determine the fate of silver species in surface water – green algae environments. [ABSTRACT FROM AUTHOR]

Silver nanoparticles (Ag-NP) are contained in many consumer products although their uptake especially by respiration bears potential risks for human health. Quantitative data about the systemic distribution of Ag-NP at the cellular level is strongly required to better understand the mode of action and to create meaningful in vitro models. In this paper we present a novel approach to identify cells in tissue sections by mass spectrometry imaging. Starting with a specific antibody bound to a cell marker protein we employed a double labelling strategy: a conventional secondary fluorescent antibody staining is followed by a labelling with a colloidal gold-coupled antibody directed against the same primary antibody. This allows identification of, e.g., regions of interest with conventional fluorescence microscopy and, thereafter, to detect identified cells by elemental mass spectrometry. The strategy circumvents the necessity to allocate mass-based signals to microscopic images. Unlike cost-intensive lanthanide-labelling the method is applicable to monoclonal and polyclonal primary antibodies. With this approach we confirmed the uptake of silver nanoparticles in alveolar macrophages and alveolar septal structures. [ABSTRACT FROM AUTHOR]

We investigated the capability of high-gain Faraday detectors equipped on a multi-collector-ICP-mass spectrometer (MFC-ICP-MS) in performing both particle size and Ag isotopic ratio determination for individual silver nanoparticles (Ag NPs). Two high-gain Faraday detectors equipped with 1013 Ω resistors were used to detect transient signals emanating from individual NPs (particle events). A continuous ion-monitoring method (CIM) was adopted to obtain reliable isotopic ratio data from the particle events. The CIM measurements of the signal intensities obtained from Ag NPs (40, 60, 80, 100, and 200 nm) exhibited a good linearity with the sizes of the Ag NPs. The variations of the measured 109Ag/107Ag ratio for the particles of each size in the isotopic ratio measurements (about 100 particles sampled per size) were about: 12% for 40 nm, 4.9% for 60 nm, 1.9% for 80 nm, 1.2% for 100 nm, and 0.26% for 200 nm. The resulting precision of the 109Ag/107Ag ratio measurements can be basically attributed to both shot noise (counting statistics) and background fluctuation on amplifiers. The data obtained here demonstrated that the MFC-ICP-MS system combined with the CIM can be employed to determine both the NP size and isotopic ratio of constituent elements. [ABSTRACT FROM AUTHOR]

Toxicological studies concerning nanomaterials in complex biological matrices usually require a carefully designed workflow that involves handling, transportation and preparation of a large number of samples without affecting the nanoparticle (NP) characteristics, as well as measurement methods that enable their reliable characterisation. This work describes method development for the determination of number concentration and size of silver nanoparticles (AgNP) in blood for the purpose of application to the typical workflow of an in vivo toxicology assessment involving blood-containing AgNP and Ag(I) leached out from medical devices. A systematic comparison of single particle detection using millisecond versus microsecond dwell times in the presence of different ionic Ag [Ag(I)]-to-AgNP ratios by spICP-MS was undertaken to achieve sufficient selectivity for the determination of NP number concentration. This was achieved for the first time in a complex media such as 2.5% tetramethylammonium hydroxide (TMAH)/0.1% Triton X-100 (v/v) diluent, which was proven to preserve nanoparticle stability upon 8 days of storage following AgNP quantitative extraction from the blood matrix. The potential of microsecond dwell time for improved discrimination of AgNP (40 nm) from Ag(I) was demonstrated for ionic to nanoparticle ratios [Ag(I)/AgNP] of up to 106-fold. For NP sizing, a systematic study of the impact of matrix-matched ionic calibration on the derived particle size by spICP-MS is also described. Three different ionic calibration media including 1% HNO3 (v/v), 1 mM trisodium citrate and 2.5% TMAH/0.1% Triton X-100 (v/v) were tested. Student t-test evidenced statistically significant differences between the slope of the calibration curve of Ag(I) in TMAH/Triton X-100 compared to HNO3 and trisodium citrate matrices, whereas no significant differences were found between the two latter media. Moreover, a good agreement was found between the particle diameter derived from spICP-MS following ionic calibration in TMAH/Triton X-100 and the diameter obtained with transmission electron microscopy (TEM), demonstrating the importance of matrix-matched calibration for NP size determination in a complex matrix using spICP-MS. Number concentration recovery measurements on blood samples spiked with AgNP and size measurements both using spICP-MS demonstrated the feasibility of the methodology developed here for potential future application to AgNP characterisation in toxicology research. [ABSTRACT FROM AUTHOR]

The ability of laser-induced breakdown spectroscopy (LIBS) to detect Cd in rice is limited. A nanoparticle enhancement method combined with film preparation to improve the detection with LIBS is proposed. The film sample was prepared by scraping the mixed rice powder and silver nanoparticle (Ag NP) suspensions onto a glass slide, which was then dried in air. Finally, the glass slide that contained the analytes and Ag NPs was used for LIBS determination. Compared with the traditional tableting method, the spectral intensity of Cd is increased by a factor of 20. Thus, the limit of detection was 0.17 μg g−1, and the limit of quantification was 0.56 μg g−1. The results demonstrate that the method of nanoparticle-enhanced LIBS (NELIBS) combined with film preparation can be used to distinguish rice with excessive Cd content. [ABSTRACT FROM AUTHOR]

The effect of the shape of the nanoparticles on the nanoparticle-enhanced LIBS (NELIBS) signal should be clarified. The present study reports on the effect of the silver (silver chloride) nanoparticle shape (nanospheres, nanocubes, and nanowires) on the LIBS signal for different target materials; two metals (aluminum and zinc) and one semiconductor (silicon). The shape enhancement factor and the plasma parameters, namely plasma temperature and electron density, have also been evaluated. Silver nanoparticles have been characterized using different techniques, including SEM, UV-vis, and XRD. The results showed that the clusters formed in the silver nanowires and nanocubes play an essential role in the laser pulse's absorption mechanism and, consequently, enhance the LIBS signal. Nanowires followed by nanocubes showed better enhancement than nanospheres, confirmed by the shape-dependent enhancement factor. However, the laser-induced plasma parameters (plasma temperature and electron density) have not been affected much by the nano-shape change. [ABSTRACT FROM AUTHOR]

Silver nanoparticles (Ag NPs) are among the most widely used engineered nanomaterials and this warrants further investigation of their behaviour and fate in the environment. To support such work, we developed new techniques for efficient tracing of Ag NPs that are produced from, and hence labelled with, enriched 109Ag (Ag-En). The methods encompass a one-step anion exchange separation of Ag from the sample matrix and precise determination of 109Ag/107Ag ratios and 109Ag abundances by multiple-collector ICP-MS. The sample preparation procedure has an Ag yield of 104 ± 13% (1 SD) and a procedural Ag blank of less than 7 pg, enabling analysis of samples with only trace Ag contents. Analyses of Ag solutions and realistic samples show that careful correction of memory effects is paramount for ensuring data quality. Using appropriate procedures, the 109Ag/107Ag ratios of samples containing Ag-En can be determined to a precision and trueness of better than about 0.5%, when more than 0.5 ng Ag are available for analysis. Even if Ag is only present at 50 pg or less, the Ag isotope ratios and Ag-En concentrations of samples can be measured to better than 5 to 10%. The methods are therefore able to resolve the presence of 1 pg of Ag-En in samples that contain as little as 10 pg and to up to 1 ng of natural Ag. As such, the techniques allow robust detection and quantification of Ag-En in environmental samples even when highly variable quantities of Ag-En and natural Ag are present. The new methodology thus enables the use of stable isotope tracing to investigate the fate of Ag NPs in complex environmental systems at dosing concentrations similar to the predicted environmental concentrations and for very small samples, whilst also providing high sample throughput. [ABSTRACT FROM AUTHOR]

Silver nanoparticles (AgNPs) are currently one of the most manufactured nanomaterials, and they have been applied in various consumer products due to their distinctive antimicrobial properties. Because of cell heterogeneity, the analysis of AgNPs in single cells after exposure is fundamental for biomedical applications or toxicological assays. Here, we developed a high-throughput method for single cell analysis by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). Single cells were efficiently trapped by a polydimethylsiloxane (PDMS) microwell array. Under optimal conditions, 60% microwells contained one single cell and 4% microwells contained two cells or more. The cells in the array were regularly distributed; thus, they could be easily targeted and ablated in a grid pattern and quantitatively analyzed by LA-ICP-MS with a high throughput. The silver mass in single 16HBE cells exposed to AgNPs showed log-normal distribution ranging from 0.80 to 383 fg Ag per cell. The average result from single cells was in good agreement with the result from the digestion of 3.0 × 106 cells. The limit of detection (LOD) and limit of quantification (LOQ) were calculated to be 0.2 fg Ag and 0.7 fg Ag, respectively. Because of its great potential in single cell analysis, LA-ICP-MS can be widely applied for single cell analysis and can offer great benefits for the study of the biological effects of metal NPs at the single-cell level. [ABSTRACT FROM AUTHOR]

In this work, a rapid method for discrimination between trace amounts of ionic silver and silver nanoparticles (AgNPs) using graphite furnace atomic absorption spectrometry (GFAAS) was developed. Systematic studies of the influence of stabilizing agents (Triton X-100, Tween 80, sodium dodecyl sulfate, tetrabutylammonium hydroxide (TBAH), tetramethylammonium hydroxide (TMAH), gelatine, and sodium citrate) on the determination of Ag+ and AgNPs of diameter 10–100 nm were undertaken. Careful optimization of atomization conditions (wall or platform atomization, heating rate, atomization temperature) was also completed. The atomization delay time (tad) was used to compare the atomization profiles of different silver species. The best resolution of signals was obtained for silver atomization from the graphite platform at 975 °C using 2 × 10−3 mol L−1 of sodium citrate as a stabilizer. The linear relationship between tad and AgNP size was applied to estimate NP diameter. The within-day repeatability of the method was 1.1–2.3% for 2.5 μg L−1 of AgNPs. The accuracy of the method was shown by the analysis of the reference material of AgNPs (RM 8017). To evaluate the utility of the proposed method for simultaneous qualitative and quantitative determination of silver forms, the analysis of model mixtures containing Ag+ and AgNPs of different sizes was done. The benefits and restrictions of the developed method are discussed in this context. Finally, the method was used for assessment of silver migration from fabrics and hygiene products. [ABSTRACT FROM AUTHOR]

To understand potential harmful effects of silver nanoparticles (AgNPs) for the growing fetus, studies dealing with the translocation and accumulation of NPs across the placental barrier are of great importance. Quantitative methods for determination of NP mass and number concentration and their size are required for studying NP accumulation in placental tissue. In the present study, we applied and compared two sample preparation techniques, alkaline and enzymatic treatment, followed by single particle ICP-MS (spICP-MS) analysis, for characterizing AgNPs spiked to human placental tissue. Both sample preparation approaches are currently used for AgNPs in biological tissues but have not been directly compared yet. We showed that the method using enzymatic tissue treatment followed by spICP-MS is efficient for determination of mass and number concentration and size distribution of AgNPs in human placental tissues. Properties of the AgNPs were preserved during enzymatic digestion and comparable with the primary particles. The matrix effect on the determination of Ag sensitivity and transport efficiency in spICP-MS analysis was systematically evaluated as well. The method was applied to human placenta, exposed to AgNPs with two different surface modifications: 27 nm polyethylene glycol (AgPEG NPs) or 34 nm sodium carboxylate groups (AgCOONa NPs) in an ex vivo human placental perfusion model. The Ag mass concentration obtained with spICP-MS following enzymatic sample pretreatment was not significantly different from the Ag concentration obtained by conventional ICP-MS analysis of acid digested tissue. With this we confirmed the ability of the procedure to quantitatively characterize AgNPs accumulated in human tissue under realistic exposure scenario. [ABSTRACT FROM AUTHOR]

The development of methods for the analysis of silver nanoparticles (AgNPs) is of special relevance to achieve detailed insights into the fate, transport and exposure of these emerging pollutants in the environment. In the present contribution, for the first time, the possibilities and drawbacks of cloud point extraction (CPE) in combination with total reflection X-ray fluorescence spectrometry (TXRF) have been evaluated for the determination of AgNPs content in soil and consumer product water extracts. The experimental conditions for the separation and preconcentration of AgNPs with different coatings (PVP, PEG and citrate) and sizes (40–100 nm) were evaluated, paying attention to possible modifications required by the characteristics of the TXRF technique. Single particle inductively coupled plasma mass spectrometry (SP-ICPMS) analysis of the same aqueous extracts was also carried out in order to confirm the presence and percentage of AgNPs. Good agreement with respect to AgNPs concentrations in the analysed soil extracts was obtained between CPE-TXRF and SP-ICPMS, confirming the absence of matrix effects for this type of sample by CPE. On the contrary, large discrepancies were found between both analytical approaches for the studied consumer product water extracts. SP-ICPMS analysis evidenced the presence of ionic silver with a heterogeneous mixture of different sizes including relatively large Ag particles (＞100 nm). This fact was also verified by SEM-EDS analysis. The results from this study highlight the necessity to study in more detail the effectiveness of existing methodologies (including CPE-based methods and SP-ICPMS) for the monitoring of AgNPs in complex aqueous matrices involving mixtures of different NPs sizes and coatings. [ABSTRACT FROM AUTHOR]

The determination of the size and size distribution of five silver nanocolloid populations has been assessed by different techniques. Transmission electron microscopy (TEM) was proposed as a reference in single particle methods. It was compared with three particle population methods: dynamic light scattering (DLS), very usual in particle population sizing, inductively coupled plasma mass spectrometry in the single particle mode (spICP-MS), and asymmetric flow field-flow fractionation (AF4) coupled with multi-angle laser light-scattering detection (MALLS) and ICP-MS. These last two methods are gaining popularity because they provide a very complete description of the particle populations of interest, enabling access to both sizing and chemical composition. Depending on the polydispersity of the particle populations, some discrepancies did arise between the different techniques. It was found that local analysis performed by TEM tends to underestimate the mean diameter, while DLS almost always yields the largest estimate of the size. spICP-MS and AF4-MALLS-ICP-MS provided results which are consistent with the reference TEM and DLS methods in simple cases of monomodal, monodisperse populations. For less uniform distributions, for which DLS was not able to resolve the different modes, spICP-MS featured better resolution between the coexisting modes than AF4-MALLS-ICP-MS, but the latter allowed detection of smaller particles. For both techniques, care must be taken in the calibration steps: quantification of the particle mass in the case of spICP-MS and elution time for AF4-MALLS-ICP-MS. The analysis of silver colloids and the calibration with ionic standards could not be performed in the same matrix, leading to different ICP-MS signal sensitivities; introduction of recovery factors in the data processing was necessary for analytical result quality. [ABSTRACT FROM AUTHOR]

The growing production and widespread application of silver nanoparticles (AgNPs) have led to their release into the environment, where they are mostly transformed to silver sulfide nanoparticles (Ag2S NPs). Thus, speciation analysis of Ag2S NPs in environmental matrices is essential for understanding the environmental process and toxic effects of AgNPs. Herein, we report the use of aged iron oxide magnetic particles (IOMPs) as magnetic solid-phase extraction adsorbents for speciation analysis of Ag2S NPs. It was found that IOMPs are excellent adsorbents for the selective extraction of silver-containing nanoparticles (AgCNPs) including Ag2S NPs, AgNPs and AgCl NPs in the presence of Ag+. More importantly, Ag2S NPs can be distinguished from the other AgCNPs by sequential elution. After pre-eluting AgNPs and AgCl NPs as Ag+ with 2% (v/v) acetic acid and IOMPs as the sacrificial oxidants, Ag2S NPs were completely eluted as a Ag(i) complex by 10 mM thiourea in 2% (v/v) acetic acid and quantified directly by inductively coupled plasma mass spectrometry (ICP-MS). While the extraction of Ag+ was negligible, the maximum extraction of AgCNPs by IOMPs was attained at pH 4.9–6.2, and the interference of humic acid in the AgCNP extraction can be efficiently eliminated by adding Ca2+. Under optimized conditions, the method provides low detection limit (0.068 μg L−1) and high reproducibility (relative standard deviations ＜ 5.1%) for Ag2S NPs. By simultaneously spiking 0.16–10.3 μg L−1 AgNPs and 0.53–14.8 μg L−1 Ag2S NPs, the Ag2S NP recoveries were in the range of 69.6–100.2% for the tap, river and lake waters; and in the range of 106.2–149.9% for the WWTP effluent due to the part sulfidation of AgNPs to Ag2S NPs. Our method is valid for the speciation analysis of Ag2S NPs in water samples, which provides an efficient approach for studying the sulfidation of AgNPs and Ag+. [ABSTRACT FROM AUTHOR]

Single particle ICP-MS (spICP-MS) is a useful tool for characterizing and quantifying suspensions of metallic nanoparticles, but there are currently limitations on the minimum size of nanoparticles that can be detected using this technique. In this study, we demonstrated the spICP-MS capabilities of a double focusing magnetic sector ICP-MS instrument for analysis of commercially available Ag NP suspensions and samples of Ag NPs suspended in natural lake water, including data on particle event integration and sizing, particle counting and measurement of dissolved Ag background. Analysis of commercially available AgNP suspensions using a dwell time of 30 us determined that the ionic background dependent size detection limit is ∼10 nm at 2.7 ng Ag L−1. In samples collected from a lake in which AgNPs were added experimentally (PVP-capped, 30–50 nm size distribution), the Ag NPs were shown to have a modal diameter of ∼20 nm, with a dissolved Ag background of 6–13 ng L−1. The minimum particle size detectable in the lake water samples was approximately 15–18 nm, depending on the dissolved Ag concentration. There was no evidence of matrix effects in lake water that would adversely affect the accuracy of the particle sizing. The determination of particle number concentrations by spICP-MS was shown to be limited by particle size dependent transport efficiencies and losses through adsorption on sample vials. Overall, while further development of the sample preparation protocols is needed, the spICP-MS technique described in this study demonstrates improved discrimination of AgNPs from dissolved Ag and a lower particle size range relative to previously described instrumental methods. [ABSTRACT FROM AUTHOR]

Single particle ICP-MS (spICP-MS) has gained great influence in the analysis of engineered nanoparticles (NPs) due to its simplicity, speed and ability to obtain a particle number size distribution. Despite its many advantages, the method is hampered by matrix effects affecting the sensitivity of the instruments. Consequently, over- or underestimated particle sizes might be obtained. To overcome these challenges, we present in this work the detection of both Ag isotopes with a quadrupole mass spectrometer for the application of isotopic dilution analysis (IDA) in combination with spICP-MS. Here, the isotopes are measured sequentially using the conventional spICP-MS integration time of 10 ms. Citrate stabilized Ag NPs of a spherical shape with the nominal diameters of 30, 40, 50 and 80 nm have been investigated. The experimental concept of adding 109Ag+ solutions to the NP suspensions resulted in the NP spikes being only visible in the 107Ag trace. Therefore, a maximum of 45% of the particles was detected compared to that by conventional spICP-MS. A modified mass flow equation was applied to determine the particle sizes, particle size distributions and particle number concentrations of various Ag NPs. The addition of different spike concentrations between 0.5 and 4 μg L−1 109Ag resulted in similar particle diameters, suggesting that the calculated diameter might be independent of the spike concentration. This would have the advantage that no size information would be needed before the analysis. By analyzing Ag NP suspensions in a simulated seawater matrix, we demonstrate its significant influence on the particle size determination using conventional spICP-MS. A lower transport efficiency of 6.1% was found in the matrix compared to 7.3% without the matrix. In our approach, the addition of the matrix influenced the NP intensity stronger than the spike signal, resulting in slightly smaller diameters using IDA–spICP-MS with the matrix compared to the results without the matrix. On the other hand, the IDA–spICP-MS approach with the matrix can result in equivalent results for the particle sizes compared with conventional spICP-MS using suspensions without the matrix. Due to the lower instrument sensitivity in the matrix, a diameter of 30 nm was found to be close to the detection limit of the instrument. [ABSTRACT FROM AUTHOR]

Single particle inductively coupled plasma mass spectrometry (spICP-MS) is a unique tool for detecting silver nanoparticles in environmental samples at concentrations similar to those predicted in surface waters. In this study, we present a novel flow injection spICP-MS method configured to allow for rapid on-line dilution at the tip of a pneumatic nebulizer. Such a sample introduction system permits the detection and characterization of silver nanoparticles in seawater at low ng Ag per L concentrations. Dilution (up to 1/80) accounts for the minimization of seawater originating spectroscopic interferences for both silver isotopes, whereas signal suppression caused by the matrix is corrected by utilizing a freshly prepared seawater solution containing well characterized silver nanoparticles (matrix matching) in order to determine ionization and transport efficiencies. Furthermore, we present a novel, yet straightforward method for determining silver nanoparticles and dissolved silver in marine microorganisms and/or interacting with natural organic matter. This method is based on the ultrasonication of filters used for sieving 15 L of seawater, once they are immersed in deionized water. The purpose of this approach is to lyse microorganism cell membranes and thus liberate their silver content. Subsequent flow injection spICP-MS allows for the determination of the silver nanoparticles and dissolved silver bio-accumulated in marine biota and/or interacting with natural organic matter for two different filter size fractions (i.e. 0.2–2 μm and 2–5 μm). Application of these methodologies for studying seawater microcosm and mesocosm systems allowed for the detailed monitoring of the fate of silver nanoparticles in the marine environment. [ABSTRACT FROM AUTHOR]

The combination of ultrasound-assisted dispersive micro solid-phase extraction (USA DMSPE), with the use of silver nanoparticles (AgNPs) as a solid sorbent, with high-resolution continuum source electrothermal atomic absorption spectrometry (HR-CS ETAAS) is proposed for the preconcentration and determination of Hg2+ ions in water samples. The main extraction and detection parameters were investigated. Effective preconcentration of trace mercury was achieved at pH 3.5 with 10 mg of AgNPs. Amalgamated mercury was dissolved in 200 μL of 7 mol L−1 HNO3 before atomic absorption spectrometry (AAS) detection. The concentration limit of detection was 0.005 ng mL−1. The achieved preconcentration factor was 15 and the relative standard deviations (RSDs, %) for real water samples were 6–11%. The accuracy of this method was evaluated by analyses of CRMs. The method has been successfully applied to the determination of mercury in three different real water samples. [ABSTRACT FROM AUTHOR]

In this work, sample losses of silver nanoparticles (Ag NPs) in asymmetrical flow field-flow fractionation (AF4) have been systematically investigated with the main focus on instrumental conditions like focusing and cross-flow parameters as well as sample concentration and buffer composition. Special attention was drawn to the AF4 membrane. For monitoring possible silver depositions on the membrane, imaging laser ablation coupled to inductively coupled plasma mass spectrometry (LA-ICP-MS) was used. Our results show that the sample residue on the membrane was below 0.6% of the total injected amount and therefore could be almost completely avoided at low sample concentrations and optimized conditions. By investigation of the AF4 flows using inductively coupled plasma mass spectrometry (ICP-MS), we found the recovery rate in the detector flow under optimized conditions to be nearly 90%, while the cross-flow, slot-outlet flow and purge flow showed negligible amounts of under 0.5%. The analysis of an aqueous ionic Ag standard solution resulted in recovery rates of over 6% and the ionic Ag content in the sample was found to be nearly 8%. Therefore, we were able to indicate the ionic Ag content as the most important source of sample loss in this study. [ABSTRACT FROM AUTHOR]

Magnetic particles covered with functionalized silver nanoparticles are used in a micro-solid phase extraction procedure for the separation and preconcentration of mercury compounds. Functionalization with the sodium salt of 2-mercaptoethane-sulphonate (MESNa) allows Hg(ii) ions to be adsorbed. When MESNa is replaced by l-cysteine, monomethyl mercury, dimethyl mercury, ethyl mercury, phenyl mercury and diphenyl mercury are also retained. After separation by means of a magnetic field, the analytes are released from the nanocomposites by treating with a small volume of a potassium iodide solution. Mercury is then measured by electrothermal atomic absorption spectrometry using silver nitrate and potassium permanganate solutions for chemical modification. The preconcentration factor is close to 200, and a detection limit of 0.01 μg L−1 mercury is achieved. The results for total mercury are verified using certified reference materials. Water and edible fish oils are analyzed for total mercury and for two fractions or mercury organic compounds with the help of a solid phase extraction cartridge. [ABSTRACT FROM AUTHOR]

Lustre is characterized by a few hundreds of nanometers thick heterogeneous metal-glassy nano-composite film. Silver and copper nanoparticles are dispersed within the outermost layers of the glaze, conferring peculiar optical properties to the whole material. Even though numerous studies have been carried out, many questions regarding the chemical composition, the mechanism of metal reduction and the optical properties of lustre still remain. Synchrotron radiation techniques are suitable for detailed studies on metal-glassy nano-composites. For example, X-ray absorption fine structure spectroscopy (EXAFS) can provide useful information on oxidized phases or atomic clusters dispersed in an amorphous medium, otherwise not achievable with diffraction techniques. In this work, we try to get information on the chemical state and local environment of metal atoms in the lustre and in the blue pigment, in order to achieve a better understanding of the reduction mechanism of different metals present and the manufacturing techniques related to different productions (Hispano-Moorish and Italian Renaissance lustred majolicas). In particular, different samples characterized by lustre and blue decorations only, produced in Spain and in central Italy in XIV–XV cent., are compared. [ABSTRACT FROM AUTHOR]

The presence of a low amount of silver nanoparticles (AgNPs) in a medium containing ammonium pyrrolidine dithiocarbamate (APDC) and cadmium ions facilitates the cloud point extraction of the Cd–APDC complex by Triton X-114. The metallic ion is completely transferred to the surfactant-rich phase and then measured by electrothermal atomic absorption spectrometry. Using a 20 mL aqueous sample containing 100 μg L−1 AgNPs and 0.075% (w/v) Triton X-114, the enrichment factor of the cadmium complex is found to be 1050, which results in a detection limit of 1 ng L−1. The procedure shows good selectivity and reproducibility close to 5%, and its reliability is verified by analyzing three water samples with a certified cadmium content. Results for other water samples as well as for beer and wine samples are also given. [ABSTRACT FROM AUTHOR]

Flow field-flow fractionation (FlFFF) with on-line inductively coupled plasma mass spectrometer (ICP-MS) was employed to investigate the association between protein and silver nanoparticles (AgNPs). In this work, bovine serum albumin (BSA), globulin, and fibrinogen were the model proteins studied. AgNPs were prepared by the reduction of silver nitrate using tannic acid as reducing and stabilizing agent. Various sizes (2.6, 10, and 26 nm) were obtained depending on the pH condition during particle preparation. The apparent association constants between BSA and AgNPs of various sizes were determined. Then, various concentrations of 2.6 nm AgNPs were incubated with plasma proteins, i.e., albumin (2.6 × 10-1 M); globulin (3.1 × 10-2 M); and fibrinogen (2.9 × 10-3 M) at 37 °C for investigation of protein-AgNPs association. Factors influencing protein-AgNPs association were investigated, including the effect of incubation time and effect of AgNPs concentration. Association between protein and AgNPs increased as the incubation time and concentration of AgNPs increased. Further, the binding stoichiometry between BSA and AgNPs was determined to be approximately 1:5 × 10-7. [ABSTRACT FROM AUTHOR]

The increasing application of silver nanoparticles (AgNP) in consumer products and their potential release into the environment call for intensive investigation of their toxicity, stability, and fate. Analytical methods that are able to detect and characterize AgNPs at low concentrations and in complex matrices are needed. Single particle inductively coupled plasma mass spectrometry (spICP-MS) has in recent years emerged to a reliable technique suitable to quantify and size nanoparticles at low concentrations. However, the size determination by means of spICP-MS depends on external calibration with nanoparticle or element standard solutions. Here, a new approach is introduced using internal calibration with isotope dilution to determine the size of different AgNPs. External calibration becomes unnecessary, leading to a more rapid nanoparticle characterization and more robustness towards matrix effects. The power of the method is shown by determining the size of 50 nm citrate capped and 80 nm PVP capped AgNPs spiked with 109Ag enriched silver standard. The method is highly reproducible and shows good agreement with results obtained by established methods. The successful size determination of AgNPs in wastewater and river water using this method demonstrates its practicability even in samples with high matrix loads. Sample preparation only requires the addition of an isotope enriched standard, which makes the method interesting for long-term studies when AgNPs have to be characterized on many different days. As an example, the size alteration of AgNPs under different conditions was monitored over a period of four days, employing the developed method of internal calibration with isotope dilution. [ABSTRACT FROM AUTHOR]

In this work, a new analytical approach based on the trapping of Se and Hg vapours using silver nanoparticles (Ag NPs) immobilized on quartz reflectors, prior to their determination by total reflection X-ray fluorescence (TXRF), is proposed. Ag NPs were synthesized by reduction of the metal precursor with a reducing agent in aqueous solution. Silanization with 3-mercaptopropyltrimethoxysilane (MPTMS) was used in order to modify the quartz reflectors and immobilize Ag NPs by interaction between the organosilane compound and Ag NPs. A comprehensive characterization of synthesized Ag NPs was carried out by Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). SeH2 and Hg(0) vapours were generated by means of a continuous flow vapour generation system and trapped onto the quartz reflector containing immobilized Ag NPs. Different parameters involved in both the Ag NP synthesis and the continuous flow system for vapour generation and preconcentration were optimized in order to obtain the best results. Detection limits were 0.18 and 0.55 mg L -1 for selenium and mercury, respectively. Enrichment factors of 265 and 175 were obtained for Se and Hg, respectively. The new method was successfully validated against three biological certified reference materials and applied to several seafood samples. Recoveries carried out on three certified reference materials were in the range 94–106% with a relative standard deviation of 5% (N = 5). [ABSTRACT FROM AUTHOR]

Engineered nanoparticles (ENPs) show new and interesting properties leading to an increased use in various application fields and have entered our daily environment (e.g., functionalized clothing, cosmetics, food, medicine). Though on the one hand nanotechnology plays a substantial role in societies' daily life, on the other the presence and behavior of ENPs in organisms and the environment is still unclear to a large extent. Furthermore, comprehensive legislative regulation is still missing. For adequate regulation a clear definition of ENPs is needed. A definition recommendation was released in 2011 by the European Commission (EC) on the basis of size and number of ENPs present within a defined size range. However, straightforward analytical techniques which easily provide information allowing for a decision (based on the EC definition) on the presence and concentration of ENPs in a given sample do not exist yet. A promising tool, offering fraction-related size information on the one hand and allowing for element-specific detection on the other is the coupling of asymmetric flow-field-flow-fractionation (AF4) with inductively coupled plasma-mass spectrometry (ICP-MS). In this work, a new strategy for quantifying silver nanoparticle (AgNP) size fractions (30 nm ± 2.1 nm, 75 nm ± 3.9 nm) after base-line AF4 separation relying on on-line ICP-MS detection combined with "post-channel" species-unspecific online isotope dilution (on-line ID) was successfully developed. A limit of detection (LOD) of 0.5 µg Ag L-1 and a limit of quantification (LOQ) of 1.6 µg Ag L-1 were achieved by the approach applied. The recovery values for the smaller size-fraction (30 nm) were in the range of 31-41% while for the larger size-fraction (75 nm) in the range of 75-78%. The overall reproducibility (RSDs, peak areas) was in between 3.4-5.4%. Validation of the on-line ID approach was achieved via off-line fraction collection and total silver determination afterwards; a bias of 2.9-16.4% between both approaches was observed indicating that the on-line ID approach is working properly. To the best of the authors' knowledge, this is the first time that species-unspecific (post-channel) on-line ID was combined with AF4/ICP-SF-MS for fraction-related quantification of AgNPs. [ABSTRACT FROM AUTHOR]

The continuing boom of nanotechnology leads to the question of the environmental fate of engineered nanoparticles. In this study an improved method for the quantification of silver nanoparticles (Ag-NPs) in environmental samples in the nanogram per litre range by means of cloud point extraction (CPE) and electrothermal atomic absorption spectrometry (ETAAS) is presented. Separation of nanoparticles from ionic silver species is achieved by addition of the ligand EDTA. A limit of detection (LoD) as low as 0.7 ng L−1 was obtained by optimizing the extraction conditions, the enrichment factor, and the ETAAS measurement conditions. In comparison to previously published studies the LoD for silver nanoparticles after CPE is improved by a factor of 10 because ETAAS detection requires no additional sample digestion after extraction. Samples of different complexity such as river water, treated and untreated municipal wastewater and synthetic solutions containing dissolved and particulate organic matter with a total organic carbon (TOC) content up to 10 mg L−1 were spiked with different concentrations of Ag-NPs and a high recovery (＞80%) was found in all cases. Due to the low LoD and high tolerance levels for other particulate matter, TOC and ionic species, selective determination of Ag-NPs in municipal wastewater and also in the effluent of sewage treatment plants is now possible. [ABSTRACT FROM AUTHOR]

Methods to detect, quantify, and characterize engineered nanoparticles (ENPs) in environmental matrices are highlighted as one of the areas of highest priority research needs with respect to understanding the potential environmental risks associated with nanomaterials. More specifically, techniques are needed to determine the size and concentration of ENPs in a variety of complex matrices. Furthermore, data should be collected at environmentally and toxicologically relevant concentrations. Both single particle inductively coupled plasma mass spectrometry (SP-ICP-MS) and asymmetrical flow field flow fractionation (AF4) ICP-MS offer substantial advantages for detecting ENPs and assessing many of the above parameters in complex matrices over traditional characterization methods such as microscopy, light scattering, and filtration. In this study, we compared the ability of two emerging techniques to detect well characterized, monodisperse silver ENPs and examined their overall applicability to environmental studies specifically with respect to their: (A) size and concentration detection limits, (B) resolution and (C) multi-form elemental analysis. We find that in terms of concentration detection limit (both, on a mass basis and particle number basis) SP-ICP-MS was considerably more sensitive than AF4-ICP-MS (ng L−1vs.μg L−1, respectively), and offers the unique ability to differentiate dissolved and nanoparticulate fractions of total metal. With a variety of optimization parameters possible, AF4-ICP-MS can detect a much smaller NP size (2 nm vs. 20 nm for SP-ICP-MS), provides the possibility for greater size resolution. [ABSTRACT FROM AUTHOR]

Engineered nanomaterials are used increasingly around the world. In recent years, environmental concerns have being raised that call for risk assessment, toxicity studies, and nanosafety policies. It is therefore important to provide analytical tools that are able to characterize various types of nanomaterials in a sensitive and fast fashion. In this study, the analytical performance of three sample introduction systems, a PFA micronebulizer with a Peltier-cooled cyclonic spray chamber (PC3), a PFA micronebulizer with a heated cyclonic spray chamber and three-stage Peltier-cooled desolvation system (APEX Q), and a monodisperse droplet generator (Microdrop) with an in-house built spray chamber, was compared for the characterization of silver nanoparticles (Ag NP) with different sizes (20–100 nm) using single particle inductively coupled plasma mass spectrometry (SP-ICP-MS). With continuous polydisperse and pulsed monodisperse droplet sample introduction, single 30 nm NP (PC3) and 20 nm NP (APEX Q, Microdrop), respectively, were successfully detected. Detection efficiencies (20–100 nm Ag NP) were in the range of 5.8 × 10−5 to 8.2 × 10−5 counts per atom, cpa (PC3), 7 × 10−5 to 9.5 × 10−5 cpa (APEX Q), and 8.1 × 10−5 to 1.2 × 10−4 cpa (Microdrop). For a given nanoparticle sample, the variation of the relative standard deviation (RSD) of the size distribution width among the three systems was found to be 1–4% (e.g. 1.3% for 100 nm Ag NP with RSDs of 16.3%, 16.8%, and 17.6% for Microdrop, APEX Q, and PC3, respectively). Size measurements performed by SP-ICP-MS were validated by transmission electron microscopy measurements. Because silver toxicity depends on the silver species in the sample, simultaneous detection of Ag NP and free Ag(i) ions was studied with droplet sample introduction. [ABSTRACT FROM AUTHOR]