Quantification Of Silver Nanoparticles Research Articles

Exploring single-particle ICP-MS as an important tool for the characterization and quantification of silver nanoparticles in a soybean cell culture

The application of nanomaterials in the plant biotechnology field is widespread for many functions, such as the enhancement of callus induction and sterilizer agents. On the other hand, the use of in vitro plant techniques has provided nanotoxicology information at a cellular level. In this context, the use of emerging analytical techniques, such as single-particle inductively coupled plasma mass spectrometry (spICP-MS), can contribute to the development of this field. This work aims to explore the use of spICP-MS to characterize and quantify silver nanoparticles (40, 60, and 80 nm) in a plant cell medium culture (Murashige and Skoog medium, or MS medium). A preliminary study was carried out to investigate the non-spectral interference caused by the matrix, and signal suppression at a high plant cell medium culture concentration (440 mg L−1) was verified; consequently, the accuracy for the mass-based concentration was found to be below 70%. However, at a low medium concentration (4.4 mg L−1), the recovery found for size, mass, and number-based concentration was higher than 80% for all nanoparticle sizes. A matrix-matching calibration was performed to overcome these interferences, and the accuracy was significantly improved. Examples of the application of spICP-MS, such as the estimation of silver nanoparticle stability in a plant cell liquid medium and silver fractionation in soybean callus samples after in vitro plant culture, were demonstrated. In conclusion, spICP-MS is an interesting and valuable approach in this research field, providing information regarding the interaction of plant cells and nanoparticles.

AF4-UV-ICP-MS for detection and quantification of silver nanoparticles in seafood after enzymatic hydrolysis

A method based on asymmetric flow field-flow fractionation (AF4) coupled to ultraviolet–visible (UV–vis) spectroscopy and inductively coupled plasma mass spectrometry (ICP-MS) has been developed for silver nanoparticles (Ag NPs) detection and quantification in bivalve molluscs. Samples were pre-treated using a conventional enzymatic (pancreatin and lipase) hydrolysis procedure (37 °C, 12 h). AF4 was performed using a regenerated cellulose (RC) membrane (10 kDa, 350 μm spacer) and aqueous 5 mM Tris-HCl pH = 7.4 as carrier. AF4 separation was achieved with a program that included a focusing step with tip and focus flows of 0.20 and 3.0 mL min−1, respectively, and an injection time of 4.0 min. Elution of different size fractions was performed using a cross flow of 3.0 mL min−1 for 15 min, followed by linear cross flow decrease for 7.5 min, and a washing step for 9.4 min with no cross flow. Several bivalve molluscs (clams, oysters and variegated scallops) were analysed for total Ag content (ICP-MS after microwave assisted acid digestion), and for Ag NPs by the method presented here. Results show that Ag NPs are detected at the same elution time than proteins (UV monitoring at 280 and 405 nm), which suggests a certain interaction occurred between Ag NPs with proteins in the enzymatic extracts. AF4-UV-ICP-MS fractograms also suggest different Ag NPs size distributions for selected samples. Membrane recoveries, determined by peak area comparison of fractograms with and without application of cross flow, were within the 49–121% range. Confirmation of the presence Ag NPs in the investigated enzymatic extracts was demonstrated by SEM after an oxidative pre-treatment based on hydrogen peroxide and microwave irradiation.

Chemical Characterization and Quantification of Silver Nanoparticles (Ag-NPs) and Dissolved Ag in Seafood by Single Particle ICP-MS: Assessment of Dietary Exposure.

This study provides a first insight on the chemical characterization and quantification of silver nanoparticles (AgNPs) and dissolved Ag in processed canned seafood products, where food-grade edible silver (E174) is not intentionally added nor is the nanoparticle contained in the food contact material. The aim was to evaluate the bioaccumulation potential of AgNPs and to contribute to the assessment of AgNPs and ionic Ag human dietary intake from processed seafood. It is known how seafood, and in particular pelagic fish, is a precious nutritional source of unsaturated fatty acids, protein, and different micronutrients. Nevertheless, it may cause possible health problems due to the intake of toxic compounds coming from environmental pollution. Among emerging contaminants, AgNPs are widely applied in several fields such as biomedicine, pharmaceutical, food industry, health care, drug-gene delivery, environmental study, water treatments, and many others, although its primary application is in accordance with its antimicrobial property. As a consequence, AgNPs are discharged into the aquatic environment, where the colloidal stability of these NPs is altered by chemical and physical environmental parameters. Its toxicity was demonstrated in in-vitro and in-vivo studies, although some findings are controversial because toxicity depends by several factors such as size, concentration, chemical composition, surface charge, Ag+ ions released, and hydrophobicity. The new emerging technique called single-particle inductively coupled plasma mass spectrometry (spICP-MS) was applied, which allows the determination of nanoparticle number-based concentration and size distribution, as well as the dissolved element. Our findings highlighted comparable mean sizes across all species analysed, although AgNPs concentrations partly follow a trophic level-dependent trend. The low mean size detected could be of human health concern, since, smaller is the diameter higher is the toxicity. Dietary intake from a meal calculated for adults and children seems to be very low. Although seafood consumption represents only a small part of the human total diet, our findings represent a first important step to understand the AgNPs dietary exposure of the human population. Further studies are needed to characterize and quantify AgNPs in a large number of food items, both processing and not, and where AgNPs are added at the industrial level. They will provide a realistic exposure assessment, useful to understand if AgNPs toxicity levels observed in literature are close to those estimable through food consumption and implement data useful for risk assessors in developing AgNPs provisional tolerable daily intake.

Ratiometric fluorescent detection of silver nanoparticles in aqueous samples using peptide-based fluorogenic probes with aggregation-induced emission characteristics

The quantification of silver nanoparticles and Ag+ contamination in the aquatic ecosystem has attracted considerable interest. Benzoimidazolyl-cyanovinylene (1) was synthesized as an aggregation-induced emission fluorophore, and a fluorescent peptidyl probe (2 and 3) bearing this fluorophore was developed. The fluorescent peptidyl probes coordinated with Ag+ selectively among various metal ions, leading to a ratiometric response to Ag+ in pure aqueous solutions. Furthermore, an “in situ” protocol was developed to quantify AgNPs using 2 with H2O2 as an oxidizing reagent. The fluorescent detection method for Ag+ and AgNPs showed promising detection properties such as high selectivity, high sensitivity, fast response, visible light excitation, well-operations in pure aqueous solution, and large fluorescent signal change. The detection limits of Ag+ (0.64 ppb) and AgNPs (1.1 ppb) were significantly low. According to the binding mode study, Ag+ induced the formation of a 2:1 complex between 2 and Ag+ and the chirality of the peptide part of the probe was not critical for this process. The formation of aggregates of the probe triggered by Ag+ from AgNPs induced a significant change in fluorescence. Furthermore, the amounts of spiked AgNPs in groundwater and tap water were quantified using the fluorescent detection method with 2.

Detection, size characterization and quantification of silver nanoparticles in consumer products by particle collision coulometry.

Silver nanoparticles (AgNPs) are widely used in industrial and consumer products owing to its antimicrobial nature and multiple applications. Consequently, their release into the environment is becoming a big concern because of their negative impacts on living organisms. In this work, AgNPs were detected at a potential of + 0.70V vs. Ag/AgCl reference electrode, characterized, and quantified in consumer products by particle collision coulometry (PCC). The electrochemical results were compared with those measured with electron microscopy and single-particle inductively coupled plasma mass spectrometry. The theoretical and practical peculiarities of the application of PCC technique in the characterization of AgNPs were studied. Reproducible size distributions of the AgNPs were measured in a range 10-100nm diameters. A power allometric function model was found between the frequency of the AgNPs collisions onto the electrode surface and the number concentration of nanoparticles up to a silver concentration of 1010L-1 (ca. 25ngL-1 for 10nm AgNPs). A linear relationship between the number of collisions and the number concentration of silver nanoparticles was observed up to 5 × 107L-1. The PCC method was applied to the quantification and size determination of the AgNPs in three-silver containing consumer products (a natural antibiotic and two food supplements). The mean of the size distributions (of the order 10-20nm diameters) agrees with those measured by electron microscopy. The areas of current spikes from the chronoamperogram allow the rapid calculation of size distributions of AgNPs that impact onto the working electrode.

Evaluation of a cloud point extraction method for the preconcentration and quantification of silver nanoparticles in water samples by ETAAS

ABSTRACTA simple and reliable analytical method using instrumentation available in most of the laboratories has been developed for the separation and determination of silver nanoparticles in water samples. Cloud point extraction (CPE) was used for the separation of silver nanoparticles (AgNPs) from the sample and these nanoparticles were then determined by electrothermal atomic absorption spectrometry (ETAAS). Parameters related to the cloud point extraction procedure (Triton X-114 concentration, type of complexing agent (EDTA or Na2S2O3), pH, incubation temperature, incubation and centrifugation time) were selected using a multivariate approach (designs of experiments); 8.6% (v/v) Triton X-114, 750 µL saturated EDTA and pH 7 were selected as the optimum conditions. Calibration standards in a concentration range from 0 to 10 µg L−1 of AgNPs were subjected to the CPE procedure to obtain quantitative recoveries. The LOD and LOQ were 0.04 and 0.13 µg L−1, respectively. The method is selective for the extraction of AgNPs, and ionic Ag remains in the aqueous phase. Single particle inductively coupled plasma mass spectrometry (SP-ICP-MS) was used to evaluate the effect of the CPE procedure in particle size, and no changes were observed. Finally, the procedure was applied to wastewater samples spiked with nanoparticles with quantitative recoveries.

Quantification of silver nanoparticles taken up by single cells using inductively coupled plasma mass spectrometry in the single cell measurement mode

A promising analytical methodology is proposed to study nanoparticle-cell interactions providing information of the number of NPs internalized by cells or externally bound to the cell surface.

Results of an interlaboratory method performance study for the size determination and quantification of silver nanoparticles in chicken meat by single-particle inductively coupled plasma mass spectrometry (sp-ICP-MS)

Single-particle inductively coupled plasma mass spectrometry (sp-ICP-MS) promises fast and selective determination of nanoparticle size and number concentrations. While several studies on practical applications have been published, data on formal, especially interlaboratory validation of sp-ICP-MS, is sparse. An international interlaboratory study was organized to determine repeatability and reproducibility of the determination of the median particle size and particle number concentration of Ag nanoparticles (AgNPs) in chicken meat. Ten laboratories from the European Union, the USA, and Canada determined particle size and particle number concentration of two chicken meat homogenates spiked with polyvinylpyrrolidone (PVP)-stabilized AgNPs. For the determination of the median particle diameter, repeatability standard deviations of 2 and 5% were determined, and reproducibility standard deviations were 15 and 25%, respectively. The equivalent median diameter itself was approximately 60% larger than the diameter of the particles in the spiking solution. Determination of the particle number concentration was significantly less precise, with repeatability standard deviations of 7 and 18% and reproducibility standard deviations of 70 and 90%.

Development of reusable magnetic chitosan microspheres adsorbent for selective extraction of trace level silver nanoparticles in environmental waters prior to ICP-MS analysis

Solid-phase extraction (SPE) based on reusable magnetic chitosan microspheres was coupled with ICP-MS for separation and quantification of silver nanoparticles (AgNPs) in the presence of silver ions in environmental water samples. The monodisperse magnetic chitosan microspheres with an average size of 2µm were engineered using suspension cross-linking technique, and characterized and investigated for its application as SPE adsorbent. Parameters affecting the SPE were optimized, and the best performance was achieved by extracting a 20mL sample (pH 4.5) with 10mg adsorbent for 90min, followed by elution with 1mL 1% (w/v) thiourea in 10% (v/v) nitric acid for 10min. The detection limit, calculated as 3s (s, standard deviation for 11 blank readings), for three AgNPs coated with polyvinyl pyrrolidone (PVP), citrate and polyvinyl alcohol (PVA) and sizes of 31, 40, 46nm, respectively, were in the range of 0.016‒0.023μg/L. The repeatability and reproducibility (RSD, n=7) at a spiking level of 0.1μg/L AgNPs were 4.2% and 8.1%, respectively. The developed method has been applied in the analysis of AgNPs in river, lake and wastewater samples, with excellent extraction efficiencies (84.9‒98.8%) for AgNPs at spiking levels of 0.86 and 8.70μg/L. The cationic chitosan microspheres showed good species selectivity and reusability for extraction of AgNPs in the presence of Ag+, and hence the proposed method is simple, cost effective and environmentally friendly.

Separation and quantification of silver nanoparticles and silver ions using reversed phase high performance liquid chromatography coupled to inductively coupled plasma mass spectrometry in combination with isotope dilution analysis

A reversed phase high performance liquid chromatography coupled to an inductively coupled plasma mass spectrometer (HPLC–ICP-MS) approach in combination with isotope dilution analysis (IDA) for the separation and parallel quantification of nanostructured and ionic silver (Ag) is presented. The main focus of this work was the determination of the ionic Ag concentration. For a sufficient stabilization of the ions without dissolving the nanoparticles (NPs), the eluent had to be initially optimized. The determined Ag ion concentration was in a good agreement with results obtained using ultrafiltration. Further, the mechanism of the NP separation in the HPLC column was investigated. Typical size exclusion effects were found by comparing results from columns with different pore sizes. Since the recovery rates decreased with increasing Ag NP size and large Ag NPs did not elute from the column, additional interactions of the particles with the stationary phase were assumed. Our results reveal that the presented method is not only applicable to Ag NPs, but also to gold and polystyrene NPs. Finally, IDA-HPLC-ICP-MS experiments in single particle mode were performed to determine the particle cut-off size. The comparison with conventional spICP-MS experiments resulted in a similar diameter and particle size distribution.

Detection and Quantification of Silver Nanoparticles at Environmentally Relevant Concentrations Using Asymmetric Flow Field-Flow Fractionation Online with Single Particle Inductively Coupled Plasma Mass Spectrometry.

The presence of silver nanoparticles (AgNPs) in aquatic environments could potentially cause adverse impacts on ecosystems and human health. However, current understanding of the environmental fate and transport of AgNPs is still limited because their properties in complex environmental samples cannot be accurately determined. In this study, the feasibility of using asymmetric flow field-flow fractionation (AF4) connected online with single particle inductively coupled plasma mass spectrometry (spICPMS) to detect and quantify AgNPs at environmentally relevant concentrations was investigated. The AF4 channel had a thickness of 350 μm and its accumulation wall was a 10 kDa regenerated cellulose membrane. A 0.02% FL-70 surfactant solution was used as an AF4 carrier. With 1.2 mL/min AF4 cross-flow rate, 1.5 mL/min AF4 channel flow rate, and 5 ms spICPMS dwell time, the AF4-spICPMS can detect and quantify 40-80 nm AgNPs, as well as Ag-SiO2 core-shell nanoparticles (51.0 nm diameter Ag core and 21.6 nm SiO2 shell), with good recovery within 30 min. This system was not only effective in differentiating and quantifying different types of AgNPs with similar hydrodynamic diameters, such as in mixtures containing Ag-SiO2 core-shell nanoparticles and 40-80 nm AgNPs, but also suitable for differentiating between 40 nm AgNPs and elevated Ag(+) content. The study results indicate that AF4-spICPMS is capable of detecting and quantifying AgNPs and other engineered metal nanomaterials in environmental samples. Nevertheless, further studies are needed before AF4-spICPMS can become a routine analytical technique.

Feasibility of the development of reference materials for the detection of Ag nanoparticles in food: neat dispersions and spiked chicken meat

The feasibility of producing colloidal silver nanoparticle reference materials and silver nanoparticle spiked reference matrix materials was investigated. Two concentrations of PVP-coated silver nanoparticle dispersions were evaluated and used to spike chicken meat, with the aim of producing a set of reference materials to support the development of analytical methods for the detection and quantification of nanoparticles in food. Aqueous silver nanoparticle (AgNP) dispersions were evaluated for their homogeneity of mass fraction and particle size and found sufficiently homogeneous to be used as reference materials. Stability studies at 4 °C, 18 °C and 60 °C demonstrated sufficient short- and long-term stability, although particle size decreases in a linear fashion at 60 °C. The AgNP dispersions were characterized for total Ag mass fraction by ICP-OES, dissolved Ag content by ultrafiltration-ICP-MS, as well as AgNP particle size by dynamic light scattering, transmission electron microscopy (TEM) and gas-phase electrophoretic molecular mobility analysis. Chicken breasts were homogenized by cryo-milling and spiked with aqueous AgNP dispersions. Rapid freezing over liquid nitrogen resulted in homogeneous and stable materials. The spiked chicken materials were characterized for their total Ag mass fraction by neutron activation analysis and for the AgNP particle size by TEM and single-particle inductively coupled plasma mass spectrometry. The observed differences in particle sizes between the spiked chicken samples and the original silver dispersions indicate relevant matrix effects. The materials demonstrate that production and characterization of reference materials for the detection and quantification of silver nanoparticles in meat are feasible, but challenges especially in assessing stability and having sufficiently precise methods for assessment of homogeneity and stability remain.

Characterization and quantification of silver nanoparticles in nutraceuticals and beverages by asymmetric flow field flow fractionation coupled with inductively coupled plasma mass spectrometry

This study evaluated the feasibility of asymmetric flow field flow fractionation coupled with inductively coupled plasma mass spectrometry (AF4-ICP-MS) for separation, characterization and quantification of silver nanoparticles (AgNPs) in complex nutraceutical and beverage samples. For improved determination, different analysis conditions were proposed depending on the NP size, i.e. below 20nm and in the 20–60nm range. After optimization of the different experimental parameters affecting the AF4 separation process and the analyte detection, the proposed methods showed a wide dynamic linear range (i.e., in the 10–1000μgL−1) and limits of detection below 28ngL−1. A previous probe ultrasonication for 90s (corresponding to 45 pulses of 2s) of the tested samples resulted in complete AgNPs disaggregation. As a result, a fast accurate determination was achieved (complete analysis was done in ca. 37min). The practicality of the proposed methodology for the intended determination was demonstrated by successful determination of the AgNPs present in a variety of nutraceuticals and a beverage at concentration levels in the 0.7–29.5×103μgL−1 range. A good agreement was observed among these concentration data and those determined by more conventional sample preparation techniques, such as ultracentrifugation and acid digestion. Also, the estimated NP sizes using AF4 compared satisfactorily with those determined by image techniques, i.e. transmission electron microscopy (TEM). All together demonstrated the utility of this novel analytical methodology for the analysis of AgNPs of different size in complex matrices.

Gold electrodes from recordable CDs for the sensitive, semi-quantitative detection of commercial silver nanoparticles in seawater media

We report the use of homemade disposable gold electrodes fabricated from commercial recordable CDs for the detection and quantification of silver nanoparticles from a consumer product in a seawater sample. The “CDtrode” is immersed in a seawater sample containing silver nanoparticles for a certain amount of time during which the silver nanoparticles adsorb onto the CDtrode surface under open circuit conditions. The CDtrode is then transferred to an aqueous electrolyte and oxidative stripping is used to determine the amount of silver nanoparticles that have become stuck to the electrode surface. Depending on immersion time and silver nanoparticle concentration, up to a full monolayer coverage of silver nanoparticles on the CDtrode surface has been achieved.

Separation and measurement of silver nanoparticles and silver ions using magnetic particles

The recent surge in consumer products and applications using metallic nanoparticles has increased the possibility of human or ecosystem exposure due to unintentional release into the environment. To protect consumer health and the environment, there is an urgent need to develop tools that can characterize and quantify these materials at low concentrations and in complex matrices. In this study, magnetic nanoparticles coated with either dopamine or glutathione were used to develop a new, simple and reliable method for the separation/pre-concentration of trace amounts of silver nanoparticles followed by their quantification using inductively coupled plasma mass spectrometry (ICP-MS). The structurally modified magnetic particles were able to capture trace amounts of silver nanoparticles (~2ppb) and concentrate (up to 250 times) the particles for analysis with ICP-MS. Under laboratory conditions, recovery of silver nanoparticles was >99%. More importantly, the magnetic particles selectively captured silver nanoparticles in a mixture containing both nano-particulate and ionic silver. This unique feature addresses the challenges of separation and quantification of silver nanoparticles in addition to the total silver in environmental samples. Spiking experiments showed recoveries higher than 97% for tap water and both fresh and saline surface water.

Sensitive Quantification of Silver Nanoparticles by Kinetic-Spectrophotometry Method in Groundwater Samples

A novel kinetic-spectrophotometry method is developed for the determination of trace amounts of silver nanoparticles (AgNPs) in groundwater samples based on their catalytic effect on the oxidation of indigo carmine by hexacyanoferrate (III) in acetate-acetic acid medium. The absorbance was measured at 612 nm with the fixed-time method. The optimization of the operating conditions regarding concentrations of the reagents and interferences was investigated. The calibration curve is linear over the concentration range 4.0–300 μg mL−1 of AgNPs with good precision and accuracy. The proposed method is a highly sensitive, selective, and relatively rapid assay of AgNPs at trace level. The method was applied to the determination of AgNPs in groundwater and a synthetic sample.

Size characterization and quantification of silver nanoparticles by asymmetric flow field-flow fractionation coupled with inductively coupled plasma mass spectrometry

A method for determining the size of silver nanoparticles and their quantification by asymmetric flow field-flow fractionation coupled with inductively coupled plasma mass spectrometry (ICP-MS) is proposed and was tested in consumer products. Experimental conditions were studied in detail to avoid aggregation processes or alteration of the original size distributions. Additionally, losses from sorption processes onto the channel membrane were minimized for correct quantification of the nanoparticles. Mobile phase composition, injection/focusing, and fractionation conditions were evaluated in terms of their influence on both separation resolution and recovery. The ionic strength, pH, and the presence of ionic and nonionic surfactants had a strong influence on both separation and recovery of the nanoparticles. In general, better results were obtained under those conditions that favored charge repulsions with the membrane. Recovery values of 83 ± 8% and 93 ± 4% with respect to the content of silver nanoparticles were achieved for the consumer products studied. Silver nanoparticle standards were used for size calibration of the channel. The results were compared with those obtained by photon correlation spectroscopy and images taken by transmission electron microscopy. The quantification of silver nanoparticles was performed by direct injection of ionic silver standard solutions into the ICP-MS system, integration of the corresponding peaks, and interpolation of the fractogram area. A limit of detection of 5.6 μg L(-1) silver, which corresponds to a number concentration of 1×10(12) L(-1) for nanoparticles of 10 nm, was achieved for an injection volume of 20 μL.