Determination of some phthalate acid esters in artificial saliva by gas chromatography-mass spectrometry after activated carbon enrichment

The determination of six phthalate acid esters was achieved in artificial saliva using gas chromatography-mass spectrometry following activated carbon enrichment of samples. Central composite experimental design was applied to optimize method parameters, such as pH, adsorption time and amount of activated carbon. The best compromise of analytical conditions for the simultaneous determination of analytes from spiked artificial saliva were found to be: pH (3), adsorption time (30 min), activated carbon amount (1.8 g L⁻¹) and elution solvent (chloroform). These conditions were applied to study the migration of phthalate acid esters from different children's toys into saliva. A horizontal agitation method was applied to extract the analytes from plastic toys into saliva for 2 h at 37 °C. The detection limits of the method were in the range of 1.3-5.1 μg L⁻¹, while the relative standard deviation (%) values for the analysis of 100 μg L⁻¹ of the analytes were below 3.0% (n = 5). Di-2-ethylhexyl phthalate was the main analyte found in these samples.     

Assesment of dimethyl phthalate removal from aqueous phase using barium hexaferrite containing magnetic beads

The barium hexaferrite (BaFe(12)O(19)) containing magnetic poly (ethylene glycol dimethacrylate-vinyl pyridine; mag-poly [EGDMA-VP]) beads (average diameter=53-212 μm) were synthesized and characterized. Their use as an adsorbent in the removal of dimethyl phthalate (DMP) from an aqueous solution was investigated. The mag-poly (EGDMA-VP) beads were prepared by copolymerizing of 4-vinyl pyridine (VP) with ethylene glycol dimethacrylate (EGDMA). The mag-poly (EGDMA-VP) beads were characterized by N(2) adsorption/desorption isotherms (BET), vibrating sample magnetometer (VSM), X-ray powder diffraction (XRD), elemental analysis, scanning electron microscope (SEM), and swelling studies. At a fixed solid/solution ratio, the various factors affecting the adsorption of DMP from aqueous solutions such as pH, initial concentration, contact time, and temperature were analyzed. The maximum DMP adsorption capacity of the mag-poly (EGDMA-VP) beads was determined as 96.2 mg/g at pH 3.0, 25 °C. All the isotherm data can be fitted with both the Langmuir and the Dubinin-Radushkevich isotherm models. The pseudo-first-order, pseudo-second-order, Ritch-second-order, and intraparticle diffusion models were used to describe the adsorption kinetics. The thermodynamic parameters obtained indicated the exothermic nature of the adsorption. The DMP adsorption capacity did not change after 10 batch successive reactions, demonstrating the usefulness of the magnetic beads in applications.     

Hexa-BODIPY Linked-Triazole Based on a Cyclotriphosphazene Core as a Highly Selective and Sensitive Fluorescent Sensor for Fe<Superscript>2+</Superscript> Ions

A new type of fluorescent chemosensor based on tethered hexa-borondipyrromethene cyclotriphosphazene platform (HBTC) linked via triazole groups was designed and synthesized. Its sensing behavior toward metal ions was investigated by ultraviolet-visible and fluorescence spectroscopies. Addition of a Fe²⁺ ion to a tetrahydrofuran solution of HBTC gave a visual color change as well as a significantly quenched fluorescence emission, while other tested 19 metal ions induced no color or spectral changes. This compound was found to be highly selective and sensitive for Fe²⁺ with a low limit of detection (2.03 μM) which is, to the best of our knowledge, the superior than the previously studied chemosensors for Fe²⁺.

Open image in new window

Graphical Abstract ?

     

Determination of di(2-ethylhexyl) phthalate migration from toys into artificial sweat by gas chromatography mass spectrometry after activated carbon enrichment

The determination of di(2-ethylhexyl) phthalate migration was achieved in artificial sweat using gas chromatography mass spectrometry following activated carbon enrichment of samples. Response surface methodology (RSM) was used to optimise the conditions for maximum recovery and to understand the significance and interaction of the factors affecting the recovery of di(2-ethylhexyl) phthalate. The best compromise of analytical conditions for the simultaneous determination of analyte from spiked artificial sweat was found to be: pH (3.1), activated carbon amount (1.4 g L^?1), adsorption time (55 min) and elution solvent (chloroform). These conditions were applied to study the migration of di(2-ethylhexyl) phthalate from different children’s toys into artificial sweat. The detection limit of the method was 13.8 μg L^?1, while the relative standard deviation (%) value for the analysis of 100 μg L^?1 of the analyte was below 3.7% (n = 5).     

Core-shell Hierarchical Enzymatic Biosensor Based on Hyaluronic Acid Capped Copper Ferrite Nanoparticles for Determination of Endocrine-disrupting Bisphenol A

A novel enzymatic electrochemical biosensor (mCuF/PANI-nf/HA/Lacc/GCE) was designed for detection of bisphenol A (BPA). The copper ferrite nanoparticles was obtained by co-precipitation and its surface was modified with -NH₂ functional organosilane. Polyaniline nanofibers were also synthesized by cyclic voltammetry and characterized by FTIR, XRD, TGA, SEM and TEM, respectively. Then, it was crosslinked with hyaluronic acid as an immobilization matrix for Laccase to adhere to surface of the modified copper ferrites. Cyclic and differential pulse voltammetries were used to evaluate the electrochemical performances of the biosensor, which has a LOD value of 5.40 nM and a LOQ value of 16.20 nM in the 0.01–7.50 μM linear working range. The biosensor was successfully applied for determination of BPA in seawater, canned water and milk samples with recoveries ranging from 96.0 % and 100.7 %. In addition, accuracy of the voltammetric determination method in the real samples was carried out by HPLC and spike/recovery test. The layer-by-layer surface modification strategy of the designed mCuF/PANI-nf/HA/Lacc/GCE biosensor opens a new perspective on both BPA determination and using biopolymer in the structure of enzymatic electrochemical biosensors.     

Gram Matrix Analysis of Finite Distance Spaces in Constant Curvature

We develop the utility of Gram matrix machinery as a tool to treat the geometry of simplices in space forms. A formula relating the determinant of a normalized Gram matrix to the geometry of the simplex it represents is presented. We then apply the tools to leaf spaces, i.e. the set of degree 1 vertices of a metric tree. One main result is that for a given metric space X there exists a constant ₀ < 0, such that X embeds into all hyperbolic spaces of curvature less than ₀, if and only if X is a leaf space.     

Quantum-information processing in strong-excitation regime with trapped ions in microcavity

A quantum information processing scheme is proposed in a system with cold trapped ions embedded in a single mode microcavity in strong excitation regime. With suitable choice of frequencies of the laser and the cavity light as well as ion-laser coupling strength, multipartite entanglement would be generated among internal states of the ions, which is insensitive to decoherence due to the cavity decay and heating of the vibrational mode of the ions. As a practical example, the specific discussion is focused on the two-ion case. Some unique features of the Bell states are presented under the framework of our model, which would be useful for quantum information processing.Received: 22 December 2003, Published online: 2 March 2004PACS: 03.67.-a Quantum information - 32.80.Lg Mechanical effects of light on atoms, molecules, and ions - 42.50.-p Quantum opticsM. Feng: Current address: Department of Mathematical Physics, National University of Ireland, Maynooth, Co. Kildare, Ireland.     

Geometric characterizations of Gromov hyperbolicity

We prove the equivalence of three different geometric properties of metric-measure spaces with controlled geometry. The first property is the Gromov hyperbolicity of the quasihyperbolic metric. The second is a slice condition and the third is a combination of the Gehring–Hayman property and a separation condition. Mathematics Subject Classification (1991) 30F45     

Compositional inhomogeneity at the epitaxial layer and substrate interface of AlGaAs/GaAs heterostructures

Carrier concentration spikes at the epilayer/substrate interface were observed in some two-dimensional electron gas AIGaAs/GaAs structures grown by low pressure organometallic vapor phase epitaxy. Using secondary ion mass spectroscopy, the carrier spikes were correlated with indium. Under certain growth conditions an anomalous interfacial layer, which is compositionally inhomogeneous, is formed producing an enhanced carrier density. Procedures are described which reduce the presence of indium at the epilayer/substrate interface and eliminate the carrier spike.