Analysis of metallic nanoparticles and their ionic counterparts in complex matrix by reversed-phase liquid chromatography coupled to ICP-MS

Effects of Platinum Nanoparticles on Rice Seedlings (Oryza sativa L.): Size-dependent Accumulation, Transformation, and Ionomic Influence

Platinum nanoparticles (PtNPs) are increasing in the environment largely due to their wide use and application in automobile and medical industries. The mechanism of uptake behavior of different-sized PtNPs and their association with PtNPs-induced phytotoxicity to plants remains unclear. The present study investigated PtNP uptake mechanisms and phytotoxicity simultaneously to further understand the accumulation and transformation dynamics. The uptake mechanisms were investigated by comparing the uptake and toxicological effects of three different-sized PtNPs (25, 50, and 70 nm) on rice seedlings across an experimental concentration gradient (0.25, 0.5, and 1 mg/L) during germination. The quantitative and qualitative results indicated that 70 nm-sized PtNPs were more efficiently transferred in rice roots. The increase in the PtNP concentration restricted the particle uptake. Particle aggregation was common in plant cells and tended to dissolve on root surfaces. Notably, the dissolution of small particles was simultaneous with the growth of larger particles after PtNPs entered the rice tissues. Ionomic results revealed that PtNP accumulation induced element homeostasis in the shoot ionome. We observed a significant positive correlation between the PtNP concentration and Fe and B accumulation in rice shoots. Compared to particle size, the exposure concentration of PtNPs had a stronger effect on the shoot ionomic response. Our study provides better understanding of the correlation of ionomic change and NP quantitative accumulation induced by PtNPs in rice seedlings.

Drawbacks in the efficient monitoring of gold nanoparticle-based cisplatin delivery systems formation by HPLC-ICP-MS

Since chemotherapy suffers many limitations related to side effects of anticancer drugs (e.g. cisplatin - CDDP), nanoparticles are probed as carriers in targeted drug delivery. Gold nanoparticles (AuNPs) are broadly investigated due to their biocompatibility, nontoxicity, and tunable surface. Despite many AuNPs-cisplatin systems (AuNP-CS) reports found in the literature, only a few include studies of their synthesis and formation efficiency using analytical tools providing simultaneously qualitative and quantitative analytical information. Therefore, this research continues our previous study of AuNP-CS formation investigated by capillary electrophoresis with inductively coupled plasma mass spectrometry (ICP-MS). Namely, it presents the analogical approach but employs the coupling of another separation technique: isocratic reversed-phase high-performance liquid chromatography. The study concerns the difficulties of analytical method optimization path and contains a discussion of the observed problematic issues related to the analysis and preparation of AuNP-CS. Moreover, the presented work confronts the performance and applicability of both tools for the scrutiny of AuNP-CS, especially considering the comparison of their resolution power.

Size characterization of nanomaterials in environmental and biological matrices through non-electron microscopic techniques

Engineered nanomaterials (ENs) can enter the environment, and accumulate in food chains, thereby causing environmental and health problems. Size characterization of ENs is critical for further evaluating the interactions among ENs in biological and ecological systems. Although electron microscope is a powerful tool in obtaining the size information, it has limitations when studying nanomaterials in complex matrices. In this review, we summarized non-electron microscope-based techniques, including chromatography-based, mass spectrometry-based, synchrotron radiation- and neutron-based techniques for detecting the size of ENs in environmental and biological matrices. The advantages and disadvantages of these techniques were highlighted. The perspectives on size characterization of ENs in complex matrices were also presented.

Current Methods and Prospects for Analysis and Characterization of Nanomaterials in the Environment

Analysis and characterization of naturally occurring and engineered nanomaterials in the environment are critical for understanding their environmental behaviors and defining real exposure scenarios for environmental risk assessment. However, this is challenging primarily due to the low concentration, structural heterogeneity, and dynamic transformation of nanomaterials in complex environmental matrices. In this critical review, we first summarize sample pretreatment methods developed for separation and preconcentration of nanomaterials from environmental samples, including natural waters, wastewater, soils, sediments, and biological media. Then, we review the state-of-the-art microscopic, spectroscopic, mass spectrometric, electrochemical, and size-fractionation methods for determination of mass and number abundance, as well as the morphological, compositional, and structural properties of nanomaterials, with discussion on their advantages and limitations. Despite recent advances in detecting and characterizing nanomaterials in the environment, challenges remain to improve the analytical sensitivity and resolution and to expand the method applications. It is important to develop methods for simultaneous determination of multifaceted nanomaterial properties for in situ analysis and characterization of nanomaterials under dynamic environmental conditions and for detection of nanoscale contaminants of emerging concern (e.g., nanoplastics and biological nanoparticles), which will greatly facilitate the standardization of nanomaterial analysis and characterization methods for environmental samples.

Cloud point extraction (CPE) combined with single particle -inductively coupled plasma-mass spectrometry (SP-ICP-MS) to analyze and characterize nano-silver sulfide in water environment

Silver Nanoparticles (Ag-NPs), an emerging type of pollutant, might occur various physical and chemical transformations, which would affect its environmental fate, transformation and biological effects. Sulfurization is the most common conversion of Ag-NPs, accompanied by the formation of nano-silver sulfide (Ag₂S-NPs). The method of Ag₂S-NPs analysis and characterization is of great significance for assessing the environmental risks of Ag. In this study, cloud point extraction (CPE) and Single Particle-Inductively Coupled Plasma-Mass Spectrometry (SP-ICP-MS) were used in combination to establish a simple and reliable analysis method to quantify Ag₂S-NPs in water, with the morphology unchanged. Non-Ag₂S-NPs were dissociated into Ag⁺ firstly, and Ag₂S-NPs and Ag⁺ were separated by CPE, followed by SP-ICP-MS analysis. The extraction rate based on particle number concentration was between (76.19 ± 0.56) % to (106.35 ± 0.00) % in environmental waters. Compared with the (76.96 ± 2.18) nm Ag₂S-NPs spiked, the particle size extracted increased slightly with (94.19 ± 2.72) nm- (97.25 ± 0.22) nm as the large-size Ag₂S-NPs originally presented in waters, instead of agglomeration. This method could be generally applicable to the analysis of Ag₂S-NPs in waters, and provide ideas for other metal sulfide nanoparticles (MS-NPs), which has certain significance.

Elemental Speciation Analysis in Environmental Studies: Latest Trends and Ecological Impact

Speciation analysis is a key aspect of modern analytical chemistry, as the toxicity, environmental mobility, and bioavailability of elemental analytes are known to depend strongly on an element’s chemical species. Henceforth, great efforts have been made in recent years to develop methods that allow not only the determination of elements as a whole, but also each of its separate species. Environmental analytical chemistry has not ignored this trend, and this review aims to summarize the latest methods and techniques developed with this purpose. From the perspective of each relevant element and highlighting the importance of their speciation analysis, different sample treatment methods are introduced and described, with the spotlight on the use of modern nanomaterials and novel solvents in solid phase and liquid-liquid microextractions. In addition, an in-depth discussion of instrumental techniques aimed both at the separation and quantification of metal and metalloid species is presented, ranging from chromatographic separations to electro-chemical speciation analysis. Special emphasis is made throughout this work on the greenness of these developments, considering their alignment with the precepts of the Green Chemistry concept and critically reviewing their environmental impact.

Speciation of platinum nanoparticles in different cell culture media by HPLC-ICP-TQ-MS and complementary techniques: A contribution to toxicological assays

Toxicological studies of nanoparticles (NPs) are highly demanded nowadays but they are very challenging. In the in vitro assays, the understanding of the role of cell culture media is crucial to derive a proper interpretation of the toxicological results and to do so, new analytical tools are necessary. In this context, an analytical strategy based on reversed-phase liquid chromatography hyphenated to inductively coupled plasma-triple quadrupole mass spectrometry (HPLC-ICP-TQ-MS) has been developed for the first time for the detection and characterization of both 5 and 30 nm PtNPs, as well as ionic platinum species, in commonly used cell culture media. For this purpose, Dulbecco's Modified Eagle Medium, DMEM-high glucose, DMEM-F12, DMEM 31053-028, and Roswell Park Memorial Institute, RPMI-1640 (supplemented with 10% fetal bovine serum (FBS) and antibiotics) at several incubation times (24, 48, and 96 h at 37 °C) were tested. After a careful optimization and analytical performance, the developed method allows to simultaneously study the oxidation process, leading to the release of ionic species, and the increase in the hydrodynamic volume of PtNPs, probably related to the formation of new biological entities (protein corona). The magnitude of both processes was found to be dependent on the tested cell culture media and incubation times. Dynamic light scattering (DLS) and high-resolution scanning electron microscopy (HR-SEM) were used as complementary techniques to study the important process of both soft and hard protein corona formation. The feasibility of the HPLC-ICP-TQ-MS to get relevant information for toxicological studies has been demonstrated and in light of our results, the influence of the cell culture media on the behavior of PtNPs should not be underestimated.

Separation and Analysis of Nanoscale Zero-Valent Iron from Soil

Nanoscale zero-valent iron (nZVI) has become one of the most used engineered nanoparticles for soil remediation. However, isolating nZVI particles from a complex soil matrix for their accurate particle characterizations and transport distance measurements is still challenging. Here, this study established a new analysis approach combining ultrasound-assisted solvent extraction, magnetic separation, and single particle inductively coupled plasma mass spectrometry (SP-ICP-MS) analysis to isolate nZVI particles from soils and quantify their concentration and size. The interference from natural Fe-containing substances on nZVI analysis could be efficiently minimized by magnetic separation and dilution. After the optimization of extraction solvent type/concentration (i.e., 2.5 mM tetrasodium pyrophosphate) and ultrasonication time (i.e., 30 min), acceptable recoveries in both particle number (62.0 ± 10.8%-96.1 ± 4.8%) and Fe mass (70.6 ± 12.0%-119 ± 18%) could be achieved for different sizes (50 and 100 nm) and concentrations (50, 100, and 500 μg g^-1) of spiked nZVI from six soils. The detection limits of particle size and concentration were approximately 43.1 nm and 50 μg nZVI per gram soil, respectively. These results provide a feasible approach to quantify the nZVI concentration and size in complex soil matrices, which will allow the improvements to characterize and track the nZVI particles in the field, promote the use of nZVI particles for soil remediation, and better assess their environmental implications.

Quantitative Detection of Zinc Oxide Nanoparticle in Environmental Water by Cloud Point Extraction Combined ICP-MS

The increasing usage of zinc oxide nanoparticles (ZnONPs) inevitably leads to their release into the environment. To understand their fate and toxicity in water systems, a reliable method for the quantitative analysis of ZnONPs in environmental waters is urgently needed to be established. In this study, a quantitative analytical method of ZnONPs in environmental waters was developed by cloud point extraction (CPE) combined inductively coupled plasma mass spectrometry (ICP-MS). To obtain high recoveries of ZnONPs, the CPE parameters including pH, surfactant concentration, salt concentration, bath temperature, and time were optimized. The results demonstrated that the addition of β-mercaptoethylamine could significantly reduce the interference of Zn2+ on the extraction of ZnONPs, while the CPE approach was not affected significantly by the typical environmental inorganic ion and ENMs (such as Au, TiO2, and Al2O3). The extraction method of ZnONPs with different diameters was also assessed, and satisfactory extraction efficiency was obtained. The results of ZnONP concentration in collected environmental water were in the range of $0.2\pm 0.009$ - $8.2\pm 1.8$  μg/L. And the recoveries of ZnONPs in different environmental waters were $62.2\pm 2.0$ - $88.1\pm 9.6\%$ at low concentration spiked levels (12.57-54.68 μg/L), demonstrating that it is efficient to extract trace ZnONPs from real environmental waters. This established method offered a reliable method for the quantitative determination of ZnONPs in environmental waters, which could further promote the study of the environmental behavior, fate, and toxicity of ZnONPs in an aqueous environment.

Evaluation of hydrodynamic chromatography coupled to inductively coupled plasma mass spectrometry for speciation of dissolved and nanoparticulate gold and silver

In this study, hydrodynamic chromatography coupled to inductively coupled plasma mass spectrometry has been evaluated for the simultaneous determination of dissolved and nanoparticulate species of gold and silver. Optimization of mobile phase was carried out with special attention to the column recovery of the different species and the resolution between them. Addition of 0.05 mM penicillamine to the mobile phase allowed the quantitative recovery of ionic gold and gold nanoparticles up to 50 nm, whereas 1 mM penicillamine was necessary for quantitative recovery of ionic silver and silver nanoparticles up to 40 nm. The resolution achieved between ionic gold and 10-nm gold nanoparticles was 0.7, whereas it ranged between 0.31 and 0.93 for ionic silver and 10-nm silver nanoparticles, depending on the composition of mobile phase. Best-case mass concentration detection limits for gold and silver species were 0.05 and 0.75 μg L^-1, respectively. The developed methods allowed the simultaneous detection of nanoparticulate and dissolved species of gold and silver in less than 10 min. Size determination and quantification of gold and silver species were carried out in different dietary supplements, showing good agreement with the results obtained by electron microscopy and total and ultrafiltrable contents, respectively. Due to the attainable resolution, the quality of the quantitative results is affected by the relative abundance of nanoparticulate and dissolved species of the element and the size of the nanoparticles if present.

Impacts of microplastics on organotins' photodegradation in aquatic environments

Microplastics are ubiquitous in natural waters and affect the environmental fate of hydrophobic organic micropollutants. This study evaluated the impacts of four microplastics, polypropylene (PP), polyethylene (PE), polystyrene (PS) and polymethyl methacrylate (PMMA), on the photodegradation of organotin compounds (OTCs) under UV₃₆₅ irradiation (2.3 ± 0.1 W m^-2). The experiments were performed by mixing PP, PE, PS or PMMA microparticles with tri-organotins in artificial seawater. The photodegradation of OTCs in microplastic suspensions was influenced by the absorptivity onto microplastics. The decomposition rate of tributyltin (TBT) in UV-irradiated PP suspensions was greater than trimethyltin (TMT) and triphenyltin (TPhT) (p < 0.01). The adsorption capacities of OTCs (e.g., TBT) on PP particle surfaces were significantly lower than those on PE surfaces (p < 0.05) but similar with those on PMMA due to the different surface areas, shapes, and surface hydrophobicity of microplastics. TBT degraded faster (9.1%) in PS than in PMMA suspension (11.2%) within 240 min, respectively. However, only less than 5.4% was photodegraded in PP suspension due to the light scattering or absorption of the large sized PP particles. This study provided new insight into the impacts of microplastics on photodegradation of micropollutants in natural waters.

Complementary techniques (spICP-MS, TEM, and HPLC-ICP-MS) reveal the degradation of 40 nm citrate-stabilized Au nanoparticles in rat liver after intraperitoneal injection

BACKGROUND

Due to the increased use of engineered nanoparticles (NPs), their tracing in environmental and biological systems is of utmost importance. Besides their accumulation within a biological specimen, little is known about their degradation and transformation into corresponding low-molecular species that might influence any toxicological impact.

ANALYTICAL METHODS

Wistar rats underwent intraperitoneal injections of 40 nm citrate-stabilized gold nanoparticles. Different liver samples were analysed for the occurrence of nanoparticles and potential degradation products by means of spICP-MS, TEM and HPLC-ICP-MS.

MAIN FINDINGS

Studies using spICP-MS revealed the presence of the originally administrated Au NPs (40 nm diameter) and some evidences of other Au-containing species due to the increased background signal. Images obtained by transmission electron microscopy (TEM) showed the predominant presence of particles of significantly smaller diameter (6 ± 2 nm). As complementary method, HPLC-ICP-MS confirmed the presence of both particle types indicating a degradation of the Au NPs accompanied by detection of low-molecular Au species.

CONCLUSIONS

This study underlines that degradation of gold nanoparticles to low-molecular gold species might have to be taken into account in future for studies on their toxicological behaviour and their potential use in clinical applications.

Characterization of Nanoparticles: Advances

Over the past two decades, the unique properties of engineered nanoparticles (NPs) have placed them at the centre of revolutionary advancements in many sectors of science, technology and commerce. Multi-technique and multi-disciplinary analytical approaches are required to identify, quantify, and characterize the chemical composition, size and size distribution, surface properties and the number and concentration of NPs. In this chapter, an overview of the recent advances in the characterization of NPs will be presented.