Single Particle ICP-MS Research Articles

Measurement of the Density of Engineered Silver Nanoparticles Using Centrifugal FFF-TEM and Single Particle ICP-MS.

A methodology has been developed to measure nanoparticle mass and density, by combining centrifugal field-flow fractionation (CeFFF; more commonly called sedimentation FFF or SdFFF) and transmission electron microscopy (TEM). Particle effective mass obtained from CeFFF retention data and particle size obtained from the TEM images were used to calculate the nanoparticle density. The method was initially applied to measure the density of monodispersed polystyrene latex nanoparticles. Measured densities for latex nanoparticles of 160-300 nm in diameter were in the range of 1041-1063 kg m-3 with standard deviations of 0.6-1.1%. Densities of engineered silver nanoparticles with nominal diameters of 30, 60, 75, and 100 nm were measured using this methodology. For all four silver nanoparticle samples, the measured densities were 18-24% lower than the nominal density of metallic silver, with an overall mean value of 7900 ± 675 kg m-3. Density values calculated using nanoparticle mass values obtained from single particle inductively coupled plasma-mass spectrometry (spICP-MS) measurements, corroborated the CeFFF-TEM results. The difference in the density of the silver nanoparticles compared to that of bulk silver suggests that the synthesis process could impart 20-37% porosity in silver nanoparticles. The data has important implications in the fields of nanomaterial, nanomedicine and nanotoxicology, where assumption of the bulk density for nanoparticles can result in erroneous estimation of parameters such as mass, size, porosity, and dosage. The presented methodology provides a straightforward and reproducible means for measurement of the density and porosity of engineered nanoparticles with a wide range of density and size.

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

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

Environmental Risk Implications of Metals in Sludges from Waste Water Treatment Plants: The Discovery of Vast Stores of Metal-Containing Nanoparticles.

Nanoparticle (NP) assessment in sludge materials, although of growing importance in eco- and biotoxicity studies, is commonly overlooked and, at best, understudied. In the present study, sewage sludge samples from across the mega-city of Shanghai, China were investigated for the first time using a sequential extraction method coupled with single particle inductively coupled plasma mass spectrometry (SP-ICP-MS) to quantify the abundance of metal-containing NPs in the extraction fractions and transmission electron microscopy to specifically identify the nanophases present. In general, most sludges observed showed high concentrations of Cr, Cu, Cd, Ni, Zn, and Pb, exceeding the maximum permitted values in the national application standard of acid soil in China. NPs in these sludges contribute little to the volume and mass but account for about half of the total particle number. Based on electron microscopy techniques, various NPs were further identified, including Ti-, Fe-, Zn-, Sn-, and Pb-containing NPs. All NPs, ignored by traditional metal risk evaluation methods, were observed at a concentration of 107 -1011 particles/g within the bioavailable fraction of metals. These results indicate the underestimate or misestimation in evaluating the environmental risks of metals based on traditional sequential extraction methods. A new approach for the environmental risk assessment of metals, including NPs, is urgently needed.

Sizing and simultaneous quantification of nanoscale titanium dioxide and a dissolved titanium form by single particle inductively coupled plasma mass spectrometry

As a consequence of their widespread use, titanium dioxide nanoparticles (TiO2NPs) have been released into the environment where they can act as stressors towards biota. For the assessment of the environmental impact of these NPs it is important to quantitatively determine their concentration, size distribution and the dissolved Ti fraction in different water samples. In the present work, a new analytical approach was applied for sizing and quantitative determination of TiO2NPs (anatase and rutile) and dissolved Ti in aqueous samples by the use of single particle inductively coupled plasma mass spectrometry (SP-ICP-MS). The accuracy of the quantification of TiO2NPs by SP-ICP-MS was verified by calculating the recoveries between the determined and expected Ti concentrations (90–100%). The size distributions of TiO2NPs calculated by SP-ICP-MS (108±10nm for rutile, 29±2nm for anatase) were in a good agreement with data obtained by TEM (96–106nm for rutile, 21–38nm for anatase) and DLS (117±22nm for rutile, 42±30nm for anatase). The influence of different dwell times on the sizing and quantification of nanoscale titanium dioxide was also examined. Low limits of detection for NP diameter (37nm) and NP concentration (3.69×10−3ngTimL−1 for rutile and 0.058×10−3ngTimL−1 for anatase) were obtained. In order to apply the procedure developed for the sizing and quantification of TiO2NPs in environmental waters, the severe Ca isobaric interference at m/z 48 was overcome by measuring the Ti on m/z 47. It was demonstrated that the procedure optimized for the determination of Ti in environmental waters can be applied in the sizing and quantification of TiO2NPs in river water samples spiked with nanoscale anatase and rutile.

Detection of TiO2 Nanoparticles in Municipal Sewage Treatment Plant and Their Characterization Using Single Particle ICP-MS.

Establishment of analytical methods for detection and characterization of nanoparticles in the environment are gaining prominence across the globe. The present study was designed to quantify titanium (Ti) and to characterize titanium dioxide nanoparticles (TNP) from a municipal sewage treatment plant, by inductively coupled plasma mass spectrometry (ICP-MS). The concentrations of Ti & TNP were 1085 & 13.6mg/kg in the influent sewage and 298 & 3.3mg/kg in the aeration tank contents, respectively. The size of TNP ranged between 71-145nm in the sludge fraction. Determining environmentally realistic concentrations of TNP could serve as a tracer material for characterization of those nanomaterials with similar size and aggregation properties. Furthermore, inference of Ti and TNP in municipal sewage in the study will also help in environmental risk assessment of nanomaterials.

Ion exchange technique (IET) to characterise Ag+ exposure in soil extracts contaminated with engineered silver nanoparticles

Environmental contextBiosolid-amended soils are likely sinks for manufactured silver nanoparticles, the environmental toxicity of which is believed to be related to the release and accumulation of Ag+ ions. This study demonstrates how an ion exchange technique can be applied to soil extracts to provide Ag+ measurements at low, environmentally relevant levels. The technique is a valuable addition to existing analytical methods for tracking the behaviour of Ag nanoparticles and Ag+ ions in the terrestrial environment. AbstractThe lack of silver speciation exposure data in toxicity studies investigating the effects of manufactured silver nanoparticles (AgNPs) in natural soil media limits the ability to discern nano-specific effects from effects of the toxic Ag+ form, which may be released from the manufactured AgNPs contained in wastewater, biosolids or soil environment. Using samples containing Ag+ or mixtures of Ag+ and AgNPs, ranging in total Ag concentrations of 10–5 to 10–9 M, and prepared in de-ionised water and filtered soil extracts, the validity of the ion exchange technique (IET) to quantify Ag+ was investigated by comparing measurements to those of an Ag+ ion selective electrode (ISE) and to the dissolved fraction from single particle inductively coupled plasma–mass spectrometry (SP-ICP-MS) analysis (SP-dissolved). When analysing samples in the filtered soil extract, IET and ISE gave comparable results down to 10–7 M, below which Ag+ activities were below the ISE detection limit. For water samples, SP-dissolved values were generally comparable or slightly greater (on average 65%) compared with IET-Ag+ at all concentrations. The high bias was likely due to inclusion of unresolved particles below the SP-ICP detection limit of 19nm. However, when analysing samples in the soil extract, SP-dissolved values were on average eight-fold greater than IET-Ag+, highlighting the effect that natural colloidal and dissolved soil constituents have on complexing Ag+, as well as the lack of specificity of the SP-dissolved analysis for the Ag+ species. IET is shown here to be a valid procedure to quantify Ag+ activity in soil extracts, and while the study highlights the limitations of using the SP-dissolved fraction to estimate this biologically relevant Ag fraction, it shows that combined, IET and SP-ICP-MS provide a valuable approach for investigating the behaviour of manufactured AgNPs in different matrixes.

Photodegradation of polymer-CNT nanocomposites: effect of CNT loading and CNT release characteristics

Single particle ICP-MS is used to characterize the evolving magnitude, rate, and form of CNT release from photodegrading polymer nanocomposites.

Detection of lead nanoparticles in game meat by single particle ICP-MS following use of lead-containing bullets.

This study investigated whether game meat may contain nanoparticles of lead from ammunition. Lead nanoparticles in the range 40 to 750nm were detected by ICP-MS in single particle mode in game shot with lead-containing bullets. The median diameter of the detected nanoparticles was around 60nm. The particle mass concentration ranged from 290 to 340ng/g meat and the particle number concentrations from 27 to 50 million particles/g meat. The size limit of detection strongly depended on the level of dissolved lead and was in the range of 40 to 80nm. In game meat sampled more than 10cm away from the wound channel, no lead particles with a diameter larger than 40nm were detected. In addition to dissolved lead in meat that originated from particulates, the presence of lead nano particles in game meat represents a hitherto unattended source of lead with a largely unknown toxicological impact to humans. Graphical Abstract Detection of lead nanoparticles in game meat by single particle ICP-MS following use of leadcontaining bullets.

Silver nanoparticles in soil: Aqueous extraction combined with single-particle ICP-MS for detection and characterization

Silver nanoparticles (AgNPs) are used in a growing number of applications and products. Previous studies showed AgNPs can leach from these products to the environment. As a result of AgNPs leaching, sediment, soil and sludge-treated soils may be contaminated with AgNPs. Methods to detect, quantify and characterize AgNPs in soil are urgently needed. This study describes the development and validation of a method for the extraction, quantification and particle size determination of AgNPs in soils. The final method consists of pre-wetting the sample followed by an aqueous extraction, using sonication to re-suspend adsorbed AgNPs, and analysis of the aqueous extract with single particle ICP-MS. Validation of the method showed that the recovery of AgNPs spiked to soil was 44% for sandy soil and 42% for clayey soil. Although this recovery is relatively low, the repeatability and reproducibility values of the particle concentration were within the limits of Horwitz ratio, which makes the method suitable for its purpose. Further, the method concentration detection limit, LODc., is 5μgkg−1 soil. The developed method can be applied in eco-toxicological and risk-assessments studies for AgNP in the soil environment.

Dissolution Behavior of Silver Nanoparticles and Formation of Secondary Silver Nanoparticles in Municipal Wastewater by Single-Particle ICP-MS.

Ag nanoparticles (nAg) are used in various consumer products and a significant fraction is eventually discharged with municipal wastewater (WW). In this study we assessed the release of Ag from polyvinylpyrrolidone (PVP)- and citrate-coated 80 nm nAg in aerobic WW effluent and mixed liquor and the related changes in nAg size, using single particle ICP-MS (spICP-MS). The concentration of dissolved (nonparticulate) Ag in WW effluent was 0.89 ± 0.05 ppb at 168 h and was 71% lower than in deionized (DI) water, in batch reactors spiked with 5 × 106 PVP-nAg particles/mL (10 μg/L), an environmentally relevant concentration. Dissolved Ag in WW was partly reformed into ∼22 nm nAgxSy by inorganic sulfides and organosulfur dissolved organic carbon (DOC) after 120 h, whereas the parent nAg mean diameter decreased to 65.89 ± 0.9 nm. Reformation of nAgxSy from Ag+ also occurred in cysteine solutions but not in DI water, or humic and fulvic acid solutions. Dissolution experiments with nAg in WW mixed liquor showed qualitatively similar dissolution trends. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) and X-ray photoelectron spectroscopy (XPS) analyses indicated binding of thiol- and amine-containing DOC as well as inorganic sulfides with nAg. Those WW components, as well as limited dissolved oxygen, decreased dissolution in WW.

High transport efficiency of nanoparticles through a total-consumption sample introduction system and its beneficial application for particle size evaluation in single-particle ICP-MS.

In order to facilitate reliable and efficient determination of both the particle number concentration (PNC) and the size of nanoparticles (NPs) by single-particle ICP-MS (spICP-MS) without the need to correct for the particle transport efficiency (TE, a possible source of bias in the results), a total-consumption sample introduction system consisting of a large-bore, high-performance concentric nebulizer and a small-volume on-axis cylinder chamber was utilized. Such a system potentially permits a particle TE of 100%, meaning that there is no need to include a particle TE correction when calculating the PNC and the NP size. When the particle TE through the sample introduction system was evaluated by comparing the frequency of sharp transient signals from the NPs in a measured NP standard of precisely known PNC to the particle frequency for a measured NP suspension, the TE for platinum NPs with a nominal diameter of 70nm was found to be very high (i.e., 93%), and showed satisfactory repeatability (relative standard deviation of 1.0% for four consecutive measurements). These results indicated that employing this total consumption system allows the particle TE correction to be ignored when calculating the PNC. When the particle size was determined using a solution-standard-based calibration approach without an NP standard, the particle diameters of platinum and silver NPs with nominal diameters of 30-100nm were found to agree well with the particle diameters determined by transmission electron microscopy, regardless of whether a correction was performed for the particle TE. Thus, applying the proposed system enables NP size to be accurately evaluated using a solution-standard-based calibration approach without the need to correct for the particle TE.

Practical limitations of single particle ICP-MS in the determination of nanoparticle size distributions and dissolution: case of rare earth oxides

The applicability of single particle ICP-MS (SP-ICP-MS) for the analysis of nanoparticle size distributions and the determination of particle numbers was evaluated using the rare earth oxide, La2O3, as a model particle. The composition of the storage containers, as well as the ICP-MS sample introduction system were found to significantly impact SP-ICP-MS analysis. While La2O3 nanoparticles (La2O3 NP) did not appear to interact strongly with sample containers, adsorptive losses of La3+(over 24h) were substantial (>72%) for fluorinated ethylene propylene bottles as opposed to polypropylene (<10%). Furthermore, each part of the sample introduction system (nebulizers made of perfluoroalkoxy alkane (PFA) or glass, PFA capillary tubing, and polyvinyl chloride (PVC) peristaltic pump tubing) contributed to La3+ adsorptive losses. On the other hand, the presence of natural organic matter in the nanoparticle suspensions led to a decreased adsorptive loss in both the sample containers and the introduction system, suggesting that SP-ICP-MS may nonetheless be appropriate for NP analysis in environmental matrices. Coupling of an ion-exchange resin to the SP-ICP-MS led to more accurate determinations of the La2O3 NP size distributions.

Silver nanoparticle behaviour in lake water depends on their surface coating

The present study examines the stability of silver nanoparticles (AgNPs) of three different coatings – citrate (CIT), polyvinyl pyrrolidone (PVP) and lipoic acid (LIP) and two sizes - 20 and 50nm in lake water (LW) over time. Using a combination of asymmetric flow field-flow fractionation (AsFlFFF), surface plasmon resonance (SPR), and single particle inductively coupled plasma mass spectrometry (SP-ICP-MS), the influence of size, surface coating, exposure time, as well as the presence and nature of dissolved organic matter (DOM) on the transformation of AgNPs at low environmental concentrations was thoroughly investigated. The results revealed that the AgNP stability in lake water are complex interplay between the surface coating characteristics, exposure time and presence and nature of DOM. Among the studied variables surface coating was found to play the major role of determining AgNPs behaviour in lake water. PVP-coated AgNPs agglomerated to a lesser extent as compared with the CIT- and LIP-AgNPs. For a given surface coating, DOM of pedogenic and aquagenic origin increased the stability of the AgNPs (LW+EPS>LW+SRHA>LW). Moreover, extracellular polymeric substances (EPS; aquagenic origin) stabilized lipoic acid-coated AgNPs more effectively than Suwannee River Humic Acids (SRHA; pedogenic origin), showing that DOM nature has to be also considered for improved understanding the AgNP stability in aquatic environment.

Separation and determination of silver nanoparticle in environmental water and the UV-induced photochemical transformations study of AgNPs by cloud point extraction combined ICP-MS

In this study, cloud point extraction (CPE) combined inductively coupled plasma mass spectrometry (ICP-MS) was used to determinate silver nanoparticles (AgNPs) in environmental water. AgNPs dispersed in water could be extracted into surfactant phase based on optimized CPE parameters which including pH, incubation temperature and equilibration time, the content of nonionic surfactants (Triton X-114, TX-114) and Na2S3O3. Good separation results of AgNPs and ionic silver Ag(I) in aqueous environment was obtained with the addition of Na2S3O3 when the concentration of Ag(I) was lower than ten times of AgNPs. High recoveries of different diameter AgNPs spiked into ultrapure water were obtained. The influence of environmentally relevant matrix on CPE of AgNPs was studied in detail. Our results showed that there were little interference of environmentally relevant ions and five representative engineering nanomaterials (ENMs) on CPE of AgNPs. Moreover high recoveries and good separation were obtained when natural organic matter (NOM) up to 30mg/L mixed with AgNPs in ultrapure water. The detection limit of AgNPs in water using CPE combined ICPMS was 5ng/L. The recoveries of the AgNPs spiked into natural and effluents water with this method were in the range of 79±1–123±13%. Furthermore CPE-ICPMS and Single particle-ICPMS were used to study the UV induced photochemical transformations of AgNPs suspension at environmental relevant concentrations.

Nanosilver conductive ink: A case study for evaluating the potential risk of nanotechnology under hypothetical use scenarios

Engineered nanomaterials (ENMs) are being incorporated into a variety of consumer products due to unique properties that offer a variety of advantages over bulk materials. Understanding of the nano-specific risk associated with nano-enabled technologies, however, continues to lag behind research and development, registration with regulators, and commercialization. One example of a nano-enabled technology is nanosilver ink, which can be used in commercial ink-jet printers for the development of low-cost printable electronics. This investigation utilizes a tiered EHS framework to evaluate the potential nano-specific release, exposure and hazard associated with typical use of both nanosilver ink and printed circuits. The framework guides determination of the potential for ENM release from both forms of the technology in simulated use scenarios, including spilling of the ink, aqueous release (washing) from the circuits and UV light exposure. The as-supplied ink merits nano-specific consideration based on the presence of nanoparticles and their persistence in environmentally-relevant media. The material released from the printed circuits upon aqueous exposure was characterized by a number of analysis techniques, including ultracentrifugation and single particle ICP-MS, and the results suggest that a vast majority of the material was ionic in nature and nano-specific regulatory scrutiny may be less relevant.

Physicochemical characterization of titanium dioxide pigments using various techniques for size determination and asymmetric flow field flow fractionation hyphenated with inductively coupled plasma mass spectrometry.

Seven commercial titanium dioxide pigments and two other well-defined TiO2 materials (TiMs) were physicochemically characterised using asymmetric flow field flow fractionation (aF4) for separation, various techniques to determine size distribution and inductively coupled plasma mass spectrometry (ICPMS) for chemical characterization. The aF4-ICPMS conditions were optimised and validated for linearity, limit of detection, recovery, repeatability and reproducibility, all indicating good performance. Multi-element detection with aF4-ICPMS showed that some commercial pigments contained zirconium co-eluting with titanium in aF4. The other two TiMs, NM103 and NM104, contained aluminium as integral part of the titanium peak eluting in aF4. The materials were characterised using various size determination techniques: retention time in aF4, aF4 hyphenated with multi-angle laser light spectrometry (MALS), single particle ICPMS (spICPMS), scanning electron microscopy (SEM) and particle tracking analysis (PTA). PTA appeared inappropriate. For the other techniques, size distribution patterns were quite similar, i.e. high polydispersity with diameters from 20 to >700 nm, a modal peak between 200 and 500 nm and a shoulder at 600 nm. Number-based size distribution techniques as spICPMS and SEM showed smaller modal diameters than aF4-UV, from which mass-based diameters are calculated. With aF4-MALS calculated, light-scattering-based “diameters of gyration” (Øg) are similar to hydrodynamic diameters (Øh) from aF4-UV analyses and diameters observed with SEM, but much larger than with spICPMS. A Øg/Øh ratio of about 1 indicates that the TiMs are oblate spheres or fractal aggregates. SEM observations confirm the latter structure. The rationale for differences in modal peak diameter is discussed.

Optimisation, evaluation and application of asymmetrical flow field-flow fractionation with single particle inductively coupled plasma mass spectrometry (SP-ICP-MS) to characterise silver nanoparticles in environmental media

The consumption of nanomaterials has been steadily increasing in various industrial and commercial sectors. For engineered nanoparticles (ENPs), the development of appropriate methods for separating, characterising and quantifying is a prerequisite for their risk assessment and evaluation in terms of environmental exposure. Asymmetrical flow field-flow fractionation (AF4) coupled with single particle inductively coupled plasma mass spectrometry (AF4/SP-ICP-MS) is considered to be a valuable tool able to achieve these goals. Studies on the evaluation of AF4 performance, however, are lacking because most previous research has considered the separation and quantification of ENPs separately without verifying the resolution and recovery regarding AF4. As a result, a biased and erroneous interpretation of AF4 capability could result. Moreover, focus has been on the characterisation of individual ENPs, although various properties of ENPs, such as the type of capping materials, greatly affect the performance of AF4. For this reason, this study focused on the optimisation of AF4 operational conditions by considering the effects of coating materials to efficiently separate silver NPs (AgNPs). In addition, the overall performance of AF4 was evaluated by comparing results obtained from various detectors, such as ultraviolet-visible spectroscopy (UV–VIS), multi-angle light scattering (MALS), dynamic light scattering (DLS), transmission electron microscopy (TEM) and SP-ICP-MS. A methodology was proposed to correct the erroneous and biased interpretation of AF4 performance in terms of signal characteristics, resolution and recovery. Then, the optimised method was applied to real aqueous samples to verify its practicality on environmental media.

Determination of gold nanoparticles in natural water using single particle-ICP-MS

A reliable method for detecting nanoparticles is necessary for the wide application of nanomaterials. Single particle-inductively coupled plasma mass spectrometry (SP-ICP-MS) was investigated to detect the size of gold nanoparticles (AuNPs) in this work. Discrimination of particle signal and iterative algorithm were used to calculate the baseline of particle signal. Influence of dwell time was discussed and 3 ms was selected as dwell time for size detection. Different AuNPs standards (30, 60, 80 and 100 nm) and mixed samples (60 and 100 nm) were determined by SP-ICP-MS and the accuracy was confirmed with reference values. The particle size detection limit was 19 nm in ultrapure water (UP water) and 31 nm in 0.1 μg/L Au3+ solution. Stability of AuNPs in ultrapure water and natural water samples was investigated by detecting size variation of AuNPs. The result shows that AuNPs are stable in aqueous environment for 6 d but degraded after 30 d.

Validation of Gold and Silver Nanoparticle Analysis in Fruit Juices by Single-Particle ICP-MS without Sample Pretreatment.

With the increasing use of nanoparticles in consumer products, the need for validated quantitation methods also rises. This becomes even more urgent because the risks of nanomaterials are still not conclusively assessed. Fast, accurate, and robust single-particle (sp) ICP-MS is a promising technique as it is capable of counting and sizing particles at very low concentrations at the same time. Another feature is the simultaneous distinction between dissolved and particulate analytes. The present study shows, for the first time to our knowledge, a method validation for the rapid analysis of silver and gold nanoparticles with sp-ICP-MS in fruit juices without sample preparation. The investigated matrices water, orange juice, and apple juice were spiked with particles and only diluted prior to measurement without using a digestion reagent. The validations regarding particle size are successful according to the German GTFCh's guideline with deviations of accuracy and precision below 15%.

Single particle ICP-MS method development for the determination of plant uptake and accumulation of CeO2 nanoparticles.

Cerium dioxide nanoparticles (CeO2NPs) are among the most broadly used engineered nanoparticles that will be increasingly released into the environment. Thus, understanding their uptake, transportation, and transformation in plants, especially food crops, is critical because it represents a potential pathway for human consumption. One of the primary challenges for the endeavor is the inadequacy of current analytical methodologies to characterize and quantify the nanomaterial in complex biological samples at environmentally relevant concentrations. Herein, a method was developed using single particle-inductively coupled plasma-mass spectrometry (SP-ICP-MS) technology to simultaneously detect the size and size distribution of particulate Ce, particle concentration, and dissolved cerium in the shoots of four plant species including cucumber, tomato, soybean, and pumpkin. An enzymatic digestion method with Macerozyme R-10 enzyme previously used for gold nanoparticle extraction fromthe tomato plant was adapted successfully for CeO2NP extraction from all four plant species. This study is the first to report and demonstrate the presence of dissolved cerium in plant seedling shoots exposed to CeO2NPs hydroponically. The extent of plant uptake and accumulation appears to be dependent on the plant species, requiring further systematic investigation of the mechanisms.