In Vitro Assessment of the Physiologically Relevant Oral Bioaccessibility of Metallic Elements in Edible Herbs Using the Unified Bioaccessibility Protocol.

In this work, the total content of seven metallic elements (Fe, Cu, Zn, Mg, Pb, Ni, and Co) in common edible herbs was determined and related to their bioaccessibility by an in vitro human digestion model. Specifically, the unified bioaccessibility protocol developed by the BioAccessibility Research Group of Europe (BARGE) was used to determine the release of each element during gastric and gastrointestinal digestion. The results show that Fe, Zn, and Mg are released during gastric digestion (34-57% Fe, 28-80% Zn, 79-95% Mg), but their overall bioaccessibility is reduced in the gastrointestinal tract (<30%).

Analyte-mediated formation and growth of nanoparticles for the development of chemical sensors and biosensors.

The cornerstone of nanomaterial-based sensing systems is the synthesis of nanoparticles with appropriate surface functionalization that ensures their stability and determines their reactivity with organic or inorganic analytes. To accomplish these requirements, various compounds are used as additives or growth factors to regulate the properties of the synthesized nanoparticles and their reactivity with the target analytes. A different rationale is to use the target analytes as additives or growth agents to control the formation and properties of nanoparticles.

Biothiol modulated growth and aggregation of gold nanoparticles and their determination in biological fluids using digital photometry.

This work describes a novel and easy to use method for the determination of biologically important thiols that relies on their ability to inhibit the catalytic enlargement of AuNP seeds in the presence of ACl ions and trigger their aggregation. UV-vis spectroscopic monitoring of the plasmon resonance bands of the formed AuNPs showed that the spectral and color transitions depend both on the concentration and the structure of biothiols. The colorimetric changes induced by biothiols were quantified in the concentration range from 5 to 300 μM in the RGB color system with digital photometry using a commercially available flatbed scanner as detector.

Development of a sequential extraction and speciation procedure for assessing the mobility and fractionation of metal nanoparticles in soils.

This study describes the development of a sequential extraction procedure for the evaluation of metal nanoparticle mobility and bioaccessibility in soils. The procedure, that was developed using gold nanoparticles (AuNPs) as model species, relies on the fractionation of nanoparticles by sequentially dissolving soil matrix components (carbonates, metal oxides, organic matter and mineral phases) in order to release the entrapped nanoparticle species in the extract solution. By summing up the concentration of AuNPs recovered in each fraction it was found that 93.

Generic Assay of Sulfur-Containing Compounds Based on Kinetics Inhibition of Gold Nanoparticle Photochemical Growth.

This work describes a new, equipment-free, generic method for the determination of sulfur-containing compounds that is based on their ability to slow down the photoreduction kinetics of gold ions to gold nanoparticles. The method involves tracking the time required for a red coloration to appear in the tested sample, indicative of the formation of gold nanoparticles, and compare the measured time relative to a control sample in the absence of the target analyte. The method is applicable with minimal and simple steps requiring only two solutions (i.

Determination of gold nanoparticles in environmental water samples by second-order optical scattering using dithiotreitol-functionalized CdS quantum dots after cloud point extraction.

This work presents a new method for the sensitive and selective determination of gold nanoparticles in water samples. The method combines a sample preparation and enrichment step based on cloud point extraction with a new detection motif that relies on the optical incoherent light scattering of a nano-hybrid assembly that is formed by hydrogen bond interactions between gold nanoparticles and dithiotreitol-functionalized CdS quantum dots. The experimental parameters affecting the extraction and detection of gold nanoparticles were optimized and evaluated to the analysis of gold nanoparticles of variable size and surface coating.

In-situ suspended aggregate microextraction of gold nanoparticles from water samples and determination by electrothermal atomic absorption spectrometry.

This work describes a new method for the extraction and determination of gold nanoparticles in environmental samples by means of in-situ suspended aggregate microextraction and electrothermal atomic absorption spectrometry. The method relies on the in-situ formation of a supramolecular aggregate phase through ion-association between a cationic surfactant and a benzene sulfonic acid derivative. Gold nanoparticles are physically entrapped into the aggregate phase which is separated from the bulk aqueous solution by vacuum filtration on the surface of a cellulose filter in the form of a thin film.

Paper-based assay of antioxidant activity using analyte-mediated on-paper nucleation of gold nanoparticles as colorimetric probes.

With the increasing interest in the health benefits arising from the consumption of dietary products rich in antioxidants, there exists a clear demand for easy-to-use and cost-effective tests that can be used for the identification of the antioxidant power of food products. Paper-based analytical devices constitute a remarkable platform for such expedient and low-cost assays with minimal external resources but efforts in this direction are still scarce. In this work we introduce a new paper-based device in the form of a sensor patch that enables the determination of antioxidant activity through analyte-driven on-paper formation of gold nanoparticles.

Rhodium nanoparticle-modified screen-printed graphite electrodes for the determination of hydrogen peroxide in tea extracts in the presence of oxygen.

In this work we describe the fabrication of nanostructured electrocatalytic surfaces based on polyethyleneimine (PEI)-supported rhodium nanoparticles (Rh-NP) over graphite screen-printed electrodes (SPEs) for the determination of hydrogen peroxide in the presence of oxygen. Rh-NP, electrostatically stabilized by citrate anions, were immobilized over graphite SPEs, through coulombic attraction on a thin film of positively charged PEI. The functionalized sensors, polarized at 0.

Programming fluid transport in paper-based microfluidic devices using razor-crafted open channels.

Manipulating fluid transport in microfluidic, paper-based analytical devices (μPADs) is an essential prerequisite to enable multiple timed analytical steps on the same device. Current methods to control fluid distribution mainly rely on controlling how slowly the fluid moves within a device or by activating an on/off switch to flow. In this Article, we present an easy approach for programming fluid transport within paper-based devices that enables both acceleration as well as delay of fluid transport without active pumping.

Ultratrace determination of silver, gold, and iron oxide nanoparticles by micelle mediated preconcentration/selective back-extraction coupled with flow injection chemiluminescence detection.

A new method has been developed for the ultrasensitive determination of silver, gold, and iron oxide nanoparticles in environmental samples. Cloud point extraction was optimized and used as a means to extract and preconcentrate all nanoparticle species simultaneously from the same sample. The extracted nanoparticles were sequentially isolated from the surfactant-rich phase by a new selective back-extraction procedure and dissociated into their precursor metal ions.

Determination of dissolved organic matter based on UV-light induced reduction of ionic silver to metallic nanoparticles by humic and fulvic acids.

We describe a novel solution-based method for the determination of dissolved organic matter (DOM) relying on the formation of silver nanoparticles (AgNPs) via photo-stimulated reduction of silver ions by humic and fulvic acids. The method is based on natural driven formation of nanoscale materials yielding a direct relationship between DOM concentration and AgNPs formation. The aqueous dispersion of the formed AgNPs show strong and uniform UV-Vis absorption bands between 450 and 550 nm irrespectively of DOM nature and properties (i.

Ligand-free gold nanoparticles as colorimetric probes for the non-destructive determination of total dithiocarbamate pesticides after solid phase extraction.

In this work, we describe a simple and sensitive non-destructive method for the determination of the total concentration of dithiocarbamate fungicides (DTCs) in real samples. The proposed method combines for the first time the benefits of an extraction method for sample clean-up and preconcentration with a sensitive colorimetric assay based on gold nanoparticle probes. In this two-step procedure, the target DTCs are isolated from the matrix and preconcentrated by solid phase extraction onto commercially available C18 sorbents.

Determination of rimantadine in human urine by HPLC using a monolithic stationary phase and on-line post-column derivatization.

In the present study, we propose the first HPLC method coupled to postcolumn derivatization for the determination of rimantadine in human urine samples. The analyte and amantadine (internal standard) were isocratically separated using an RP monolithic stationary phase (100 × 4.6 mm id) with a mobile phase consisting of CH3OH/phosphate buffer (25 mmol/L, pH 3.

Development of a generic assay for the determination of total trihydroxybenzoate derivatives based on gold-luminol chemiluminescence.

A selective assay for the determination of one of the most important class of phenolic compounds, namely trihydroxybenzoates (monomeric and polymeric compounds having at least one gallate moiety) based on their enhancing effect on the chemiluminogenic reaction between gold ions and luminol is described for the first time. In the presence of trihydroxybenzoate derivatives, the light emission generated when alkaline luminol is oxidized by gold ions is amplified several orders of magnitude compared to other common phenolic compounds which exhibit minor reactivity or no reactivity at all (e.g.

Dispersive micro-solid phase extraction of ortho-phosphate ions onto magnetite nanoparticles and determination as its molybdenum blue complex.

A direct microextraction method, employing dispersive micro-solid phase extraction (μ-SPE) of ortho-phosphate (o-PO(4)(3-)) anions onto ferromagnetic nanoparticles (MNPs) is described in this work for the first time. The method exploits the complexation of phosphate ions on the surface of positively charged magnetite nanoparticles through the formation of an inner sphere complex, which are separated from the bulk aqueous phase with the application of an adscititious magnetic field. Phosphates are eluted with sodium bicarbonate and determined spectrophotometrically as their phosphomolybdenum blue complex.

Synthetic membranes (vesicles) in inorganic ion analysis: a review.

Vesicles are structures of amphiphile molecules occurring through a self-aggregation process at the molecular or nano scale level with a large structural variety and diverse properties providing a reaction environment for chemical reactions that resembles that of natural systems. Their high versatility and recognized utility in various applications have triggered a interdisciplinary scientific endeavor over their formation, characterization and potential applications with impressive results. However, in the vastness of applications surrounding vesicular structures, their utility in analytical chemistry has only received minor attention.

Multivariate chemometric discrimination of cigarette tobacco blends based on the UV-Vis spectrum of their hydrophilic extracts.

The application of UV-Vis spectrophotometry as an alternative or complementary approach to the classification of tobacco products is presented in this work for the first time. Two hundred fifty samples from five different cigarette brands composed of single and mixed tobacco blends were examined for that purpose on the basis of the UV-Vis spectrum of their aqueous extracts. Data transformation based on the normalization of absorbance intensities as a function of sample weight was employed in order to account for differences in the relative intensities of each sample.

Monitoring and classification of wastewater quality using supervised pattern recognition techniques and deterministic resolution of molecular absorption spectra based on multiwavelength UV spectra deconvolution.

A field flow approach for the in situ monitoring of wastewater quality is developed and assessed in this work, based on a combination of methods employing deconvolution of molecular absorption spectra and in situ/on-line analysis of wastewater effluent of various origin. The approach involves in situ immersion probes to monitor basic physicochemical parameters followed by UV spectrum deconvolution in order to provide a rapid estimate of organic matter, suspended solids and nitrate and on-line analysis of phosphates in a fully automated setup. The collected data are then treated with a series of supervised pattern recognition techniques in order to classify wastewater effluent according to their origin in three major categories namely municipal, industrial and hospital.

Alkaline earth metal effect on the size and color transition of citrate-capped gold nanoparticles and analytical implications in periodate-luminol chemiluminescence.

Citrate-modified gold nanoparticles were found to undergo size and color transition upon interaction with alkaline earth metals. At low concentrations, metal ions coordinate with AuNPs via citrate boding inducing aggregation which results in size increase as evidenced by the decrease in their plasmon bandwidth. As the concentration increases further, color transition from red to blue is observed which is no longer attributed to aggregation but to specific ion adsorption phenomena.

A fast assay of water hardness ions based on alkaline earth metal induced coacervation (HALC).

In this work, a rapid assay of water hardness is presented based on the formation of a coacervate phase made up of multilamellar vesicles and close bilayers produced upon the reaction of alkaline earth metals with a carboxylate anionic surfactant in the presence of a co-surfactant (methanol). The procedure exploits the light scattering abilities of the coacervate phase which can be logarithmically linked to total hardness as CaCO(3) equivalents via spectrophotometric detection at 350 nm. The method, abbreviated as HALC, stemming from hardness by alkaline earth metal coacervation, is straightforwardly applicable overcoming the requirement for regulation of the experimental parameters involved in the determination procedure.

Development of a chromium speciation probe based on morphology-dependent aggregation of polymerized vesicle-functionalized gold nanoparticles.

In this work, a new approach for visual sensing of Cr3+ in aqueous solutions is presented, based on the morphological changes induced by Cr3+ on (4-carboxybenzyl)bis[2-(undec-10-enyloxycarbonyl)ethyl]methylammonium bromide (4-CBUAB)-polymerized vesicles. CTAB-stabilized gold nanoparticles (GNPs) react with 4-CBUAB-polymerized vesicles to form aggregates via vesicle-micelle interactions, which does not proceed further because of vesicle-vesicle repulsive forces, creating a large polymerized vesicle-gold nanoparticle (PV-GNP) conjugate. The incorporation of Cr3+ through the 4-CBUAB polymeric membrane induces structural perturbations on the polymerized vesicle morphology by swelling of the lamellar phase which is reflected in the morphology of the polymerized vesicle-gold nanoparticle conjugate assembly.

Periodate oxidation and its contribution to instrumental methods of micro-analysis--a review.

A comprehensive review that summarizes the periodate oxidation contribution to the development of selective instrumental methods of micro-analysis in the fields of electrochemistry, spectrophotometry, luminometry, chromatography, as well as studies on successful fabrication of sensors or labeling techniques are given in this review.

On-line derivatization coupled to flow injection permanganate chemiluminescence detection of total carbonyl compounds in natural waters and drinking water.

This work describes the development of a fast assay for the determination of low molecular weight carbonyl compounds based on the oxidative chemiluminescence of 2,4-dinitrophenylhydrazine with acidic permanganate, which is enhanced during conversion to the corresponding phenylhydrazone-carbonyl derivatives. By exploiting the common derivatization pathway and oxidation mechanism of phenylhydrazones under kinetically controlled conditions in a flow configuration, a common light emission is produced which corresponds to the total aqueous concentration of carbonyl compounds. The experimental conditions that afford the optimum analytical features were optimized for acetone, acetaldehyde and formaldehyde which constitute the most abundant carbonyl compounds in environmental samples.

Indirect chemiluminescence-based detection of mefenamic acid in pharmaceutical formulations by flow injection analysis and effect of gold nanocatalysts.

A highly sensitive flow injection-chemiluminescence detection (FI-CL) method based on periodate oxidation of two popular luminescent compounds for the determination of mefenamic acid (MFA) is presented. The method is an indirect CL detection method based on the CL emission generated during the oxidation of Pyrogallol (Pg) or Luminol (Lu) with the excess of periodate that remains after oxidation of MFA within the time period of 15 min. The MFA calibration curves obtained with either luminescent compounds were linear over a wide concentration range, depending on the system employed, offering detection limits in the range of low to ultra-low microg L(-1) levels.