Comparative study of extraction methods of silver species from faeces of animals fed with silver-based nanomaterials.

Extractions methods based on ultrapure water, tetramethylammonium hydroxide (TMAH), and tetrasodium pyrophosphate (TSPP) were applied to faeces collected from two in vivo experiments of pigs and chickens fed with a silver-based nanomaterial to study the fate and speciation of silver. For TMAH extraction, cysteine and CaCl were used to evaluate their stabilization effect on the silver forms. The analytical techniques single-particle inductively coupled plasma mass spectrometry (SP-ICP-MS), hydrodynamic chromatography hyphenated to ICP-MS (HDC-ICP-MS) and asymmetric flow field flow fractionation coupled to ICP-MS (AF4-ICP-MS) were applied to the simultaneous detection of particulate and dissolved silver.

How to trust size distributions obtained by single particle inductively coupled plasma mass spectrometry analysis.

Single particle inductively coupled plasma mass spectrometry (SP-ICP-MS) is a technique widely used to obtain direct information about the number concentration and the size distribution of nanoparticles in liquid suspensions. However, its methods still lack clear quality control strategies to confirm the validity of the information derived from them. Only the detection of the complete size distribution of the nanoparticles in a sample over the size critical value ensures obtaining unbiased quantitative information, otherwise information should be restricted to report the presence of nanoparticles over a certain size and number concentration since their actual total number concentration is underestimated and the size overestimated.

Analytical applications of single particle inductively coupled plasma mass spectrometry: a comprehensive and critical review.

Single particle inductively coupled plasma mass spectrometry (SP-ICP-MS) refers to the use of ICP-MS as a particle counting technique. When ICP-MS measurements are performed at very high data acquisition frequencies, information about (nano)particles containing specific elements and their dissolved forms can be obtained (element mass per particle, size and number and mass concentrations). As a result of its outstanding performance, SP-ICP-MS has become a relevant technique for the analysis of complex samples containing inorganic nanoparticles.

How the use of a short channel can improve the separation efficiency of nanoparticles in asymmetrical flow field-flow fractionation.

The use of a commercially available short length channel (14 cm length) is proposed to improve the efficiency associated to the separation by asymmetrical flow field-flow fractionation of particles in the nanometer range respect to a standard channel (27 cm length). The effect of channel length on elution times, separation efficiency and resolution have been studied. Polystyrene particles between 50 and 500 nm in size have been used to compare the behavior of both channels.

Size characterization and quantification of titanium dioxide nano- and microparticles-based products by Asymmetrical Flow Field-Flow Fractionation coupled to Dynamic Light Scattering and Inductively Coupled Plasma Mass Spectrometry.

A procedure for the size characterization and quantification of titanium dioxide (TiO) nano- and microparticles by Asymmetric Flow Field-Flow Fractionation (AF4) coupled to Dynamic Light Scattering (DLS) and Inductively Coupled Plasma Mass Spectrometry (ICP-MS) is described. Different strategies for size characterization with size standards and the use of the DLS signal for the estimation of hydrodynamic diameters are evaluated. The procedure has been applied to the characterization of TiO nanoparticles in photocatalytic products and crab sticks (surimis), where TiO is present as E171 food additive.

Iron oxide - clay composite vectors on long-distance transport of arsenic and toxic metals in mining-affected areas.

Mine wastes from abandoned exploitations are sources of high concentrations of hazardous metal(oid)s. Although these contaminants can be attenuated by sorbing to secondary minerals, in this work we identified a mechanism for long-distance dispersion of arsenic and metals through their association to mobile colloids. We characterize the colloids and their sorbed contaminants using spectrometric and physicochemical fractionation techniques.

Evaluation of number concentration quantification by single-particle inductively coupled plasma mass spectrometry: microsecond vs. millisecond dwell times.

The quality of the quantitative information in single-particle inductively coupled plasma mass spectrometry (SP-ICP-MS) depends directly on the number concentration of the nanoparticles in the sample analyzed, which is proportional to the flux of nanoparticles through the plasma. Particle number concentrations must be selected in accordance with the data acquisition frequency, to control the precision from counting statistics and the bias, which is produced by the occurrence of multiple-particle events recorded as single-particle events. With quadrupole mass spectrometers, the frequency of data acquisition is directly controlled by the dwell time.

Size determination and quantification of engineered cerium oxide nanoparticles by flow field-flow fractionation coupled to inductively coupled plasma mass spectrometry.

Facing the lack of studies on characterization and quantification of cerium oxide nanoparticles (CeO2 NPs), whose consumption and release is greatly increasing, this work proposes a method for their sizing and quantification by Flow Field-flow Fractionation (FFFF) coupled to Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). Two modalities of FFFF (Asymmetric Flow- and Hollow Fiber-Flow Field Flow Fractionation, AF4 and HF5, respectively) are compared, and their advantages and limitations discussed. Experimental conditions (carrier composition, pH, ionic strength, crossflow and carrier flow rates) are studied in detail in terms of NP separation, recovery, and repeatability.

Combining single-particle inductively coupled plasma mass spectrometry and X-ray absorption spectroscopy to evaluate the release of colloidal arsenic from environmental samples.

Detection and sizing of natural colloids involved in the release and transport of toxic metals and metalloids is essential to understand and model their environmental effects. Single-particle inductively coupled plasma mass spectrometry (SP-ICP-MS) was applied for the detection of arsenic-bearing particles released from mine wastes. Arsenic-bearing particles were detected in leachates from mine wastes, with a mass-per-particle detection limit of 0.

Detection, characterization and quantification of inorganic engineered nanomaterials: A review of techniques and methodological approaches for the analysis of complex samples.

The increasing demand of analytical information related to inorganic engineered nanomaterials requires the adaptation of existing techniques and methods, or the development of new ones. The challenge for the analytical sciences has been to consider the nanoparticles as a new sort of analytes, involving both chemical (composition, mass and number concentration) and physical information (e.g.

Colloidal mobilization of arsenic from mining-affected soils by surface runoff.

Scorodite-rich wastes left as a legacy of mining and smelting operations pose a threat to environmental health. Colloids formed by the weathering of processing wastes may control the release of arsenic (As) into surface waters. At a former mine site in Madrid (Spain), we investigated the mobilization of colloidal As by surface runoff from weathered processing wastes and from sediments in the bed of a draining creek and a downstream sedimentation-pond.

Suitability of analytical methods to measure solubility for the purpose of nanoregulation.

Solubility is an important physicochemical parameter in nanoregulation. If nanomaterial is completely soluble, then from a risk assessment point of view, its disposal can be treated much in the same way as "ordinary" chemicals, which will simplify testing and characterisation regimes. This review assesses potential techniques for the measurement of nanomaterial solubility and evaluates the performance against a set of analytical criteria (based on satisfying the requirements as governed by the cosmetic regulation as well as the need to quantify the concentration of free (hydrated) ions).

Arsenic speciation in the dispersible colloidal fraction of soils from a mine-impacted creek.

Arsenic and iron speciation in the dispersible colloid fraction (DCF; 10-1000 nm) from an As-rich mine waste pile, sediments of a streambed that collects runoff from waste pile, the streambed subsoil, and the sediments of a downstream pond were investigated by combining asymmetrical-flow field-flow fractionation (AsFlFFF)/inductively-coupled plasma-mass spectrometry (ICP-MS), transmission electron microscopy (TEM) and X-ray absorption (XAS) spectroscopy. Calcium, Fe and As (Fe/As molar ratio ∼ 1) were the main components of the DCF from waste pile. TEM/EDS and As and Fe XAS analysis revealed the presence of nanoparticle scorodite in this same DCF, as well as Fe nanoparticles in all samples downstream of the waste pile.

An insight into silver nanoparticles bioavailability in rats.

A comprehensive study of the bioavailability of orally administered silver nanoparticles (AgNPs) was carried out using a rat model. The silver uptake was monitored in liver and kidney tissues, as well as in urine and in feces. Significant accumulation of silver was found in both organs, the liver being the principal target of AgNPs.

Single particle inductively coupled plasma mass spectrometry: a powerful tool for nanoanalysis.

Single particle inductively coupled plasma mass spectrometry is an emergent ICPMS method for detecting, characterizing, and quantifying nanoparticles. Although the number of applications reported to date is limited, the relatively simple instrumental requirements, the low number concentration detection levels attainable, and the possibility to detect both the presence of dissolved and particulate forms of an element make this methodology very promising in the nanoscience related areas.

Detection and characterization of silver nanoparticles and dissolved species of silver in culture medium and cells by AsFlFFF-UV-Vis-ICPMS: application to nanotoxicity tests.

A methodology based on Asymmetric Flow Field-Flow Fractionation (AsFlFFF) coupled with UV-Vis absorption spectrometry and ICP mass spectrometry (ICPMS) has been developed and applied to the study of silver nanoparticles (AgNPs) and dissolved species of silver in culture media and cells used in cytotoxicity tests. The effect of a nano-silver based product (protein stabilized silver nanoparticles ca. 15 nm average diameter) on human hepatoma (HepG2) cell viability has been studied.

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.

Study of the size-based environmental availability of metals associated to natural organic matter by stable isotope exchange and quadrupole inductively coupled plasma mass spectrometry coupled to asymmetrical flow field flow fractionation.

The determination of the isotopically exchangeable fraction of metals in environmental solid samples (soils, composts, sediments, sludges, etc.) is used to know the amount of metal potentially available (E-value). Stable isotopes can be used for determination of E-values through the analysis of the aqueous phases from spiked suspensions.

Metal associations to microparticles, nanocolloids and macromolecules in compost leachates: size characterization by asymmetrical flow field-flow fractionation coupled to ICP-MS.

A methodological approach based on the size characterization of environmental microparticles (size larger than 1 microm), nanocolloids (1 microm to 15 nm) and macromolecules (lower than 1000 kDa) by asymmetrical flow field-flow fractionation (AsFlFFF), taking advantage of both normal and steric elution modes, is presented. The procedure was optimized to minimize the potential alteration of the size distribution and metal associations of the species characterized. Prior to separation by AsFlFFF, samples are subjected to gravitational settling of the solid suspension, followed by a centrifugation of the settled sample.

A speciation methodology to study the contributions of humic-like and fulvic-like acids to the mobilization of metals from compost using size exclusion chromatography-ultraviolet absorption-inductively coupled plasma mass spectrometry and deconvolution analysis.

High performance size-exclusion chromatography (HP-SEC) with UV absorption for organic matter detection and inductively coupled plasma mass spectrometry (ICP-MS) for elemental detection have been used to study the mobilization of metals from compost as a function of pH and the molecular mass of their complexes with dissolved organic matter (DOM). Due to its heterogeneous nature, organic matter mobilized from compost shows a continuous distribution of molecular masses in the range studied (up to 80kDa). In order to differentiate between the contribution of humic and fulvic acids (FA) to the organic matter mobilized in the pH range 5-10, their UV absorption chromatographic profiles have been deconvoluted with respect to the adjusted gaussian profiles of the humic and fulvic acids isolated from compost.

Electrochemical hydride generation as a sample-introduction technique in atomic spectrometry: fundamentals, interferences, and applications.

Electrochemical hydride generation (EC-HG) has been proposed as a valid alternative to chemical generation as a sample-introduction technique in atomic spectrometry. In this review fundamental aspects of the technique are revised, including designs of electrolytic cells, mechanisms of the generation process, and interferences caused by the presence of different species. Special attention is paid to the role of the configuration of the cathodes and their materials on the efficiency of hydride generation and on interferences from concomitant species.

Mobilization and speciation of chromium in compost: a methodological approach.

An integral approach to study the mobility of chromium in compost is presented. The approach is based on batch pH dependence leaching tests and the analysis of the leachates for total chromium, chromium(VI) and complexes of chromium(III) with natural organic matter. As leachings are performed with no aggressive reagents (ultrapure water with added nitric acid or potassium hydroxide), the method can be considered a good approach to simulate natural scenarios.

Multielement characterization of metal-humic substances complexation by size exclusion chromatography, asymmetrical flow field-flow fractionation, ultrafiltration and inductively coupled plasma-mass spectrometry detection: a comparative approach.

The use of three different separation techniques, ultrafiltration (UF), high performance size exclusion chromatography (HPSEC) and asymmetrical flow field-flow fractionation (AsFlFFF), for the characterization of a compost leachate is described. The possible interaction of about 30 elements with different size fractions of humic substances (HS) has been investigated coupling these separation techniques with UV-vis absorption spectrophotometry and inductively coupled plasma-mass spectrometry (ICP-MS) as detection techniques. The organic matter is constituted by a polydisperse mixture of humic substances ranging from low molecular weights (around 1kDa) to significantly larger entities.

Flow injection electrochemical hydride generation of hydrogen selenide on lead cathode: critical study of the influence of experimental parameters.

A flow injection system for the determination of selenium by electrochemical hydride generation and quartz tube atomic absorption spectrometry is described. The generator consists of an electrolytic flow-through cell with a concentric arrangement and a packed cathode made of particulated lead. The influences of sample flow rate, carrier gas flow rate and electrolysis current on the hydrogen selenide generation have been critically studied.