Octadecylsilane-modified silicas in the adsorption of toluene

A series of octadecylsilane-modified silicas were prepared by sol-gel and grafting methods. Carbon contents and octadecyl chain conformations were shown to depend on the preparative route. Grafting engenders a low carbon content and a liquid-like chain conformation, while the sol-gel method affords a much higher carbon content and a crystalline conformation. The relationships between the toluene adsorption of the hybrid silicas and their chain conformations, their carbon contents and their textural characteristics are discussed. These sorbents, when used in combination with ultraviolet diffuse reflectance spectroscopy (UV DRS), can be employed as a rapid screening method for detection of aromatic compounds in water and air environmental matrices. Figure Octadecylsilane-modified silicas in the adsorption of toluene     

A new vapor generation system for mercury species based on the UV irradiation of mercaptoethanol used in the determination of total and methyl mercury in environmental and biological samples by atomic fluorescence spectrometry

A new vapor generation system for mercury (Hg) species based on the irradiation of mercaptoethanol (ME) with UV was developed to provide an effective sample introduction unit for atomic fluorescence spectrometry (AFS). Preliminary investigations of the mechanism of this novel vapor generation system were based on GC–MS and FT–IR studies. Under optimum conditions, the limits of determination for inorganic divalence mercury and methyl mercury were 60 and 50 pg mL⁻¹, respectively. Certified reference materials (BCR 463 tuna fish and BCR 580 estuarine sediment) were used to validate this new method, and the results agreed well with certified values. This new system provides an attractive alternative method of chemical vapor generation (CVG) of mercury species compared to other developed CVG systems (for example, the traditional KBH₄/NaOH–acid system). To our knowledge, this is the first systematic report on UV/ME-based Hg species vapor generation and the determination of total and methyl Hg in environmental and biological samples using UV/ME–AFS. Figure A new vapor generation system for mercury species using mercaptoethanol under UV irradiation was developed as an effective sample introduction unit for atomic fluorescence spectrometry     

UV–vis spectroscopic study directly detecting inorganic phosphorus in urine and our reagent kit

The determination of inorganic phosphorus in human urine is very important, since it has diagnostic value in some clinical cases. Here we apply a simple, sensitive and direct method to determine inorganic phosphorus in urine. This new ensemble is prepared by adding ytterbium chloride and pyrocatechol violet in a 2:1 molar ratio in an aqueous solution of 10 mM 2-[4-(2-hydroxyethyl)-1-piperazinyl]ethanesulfonic acid buffer at pH 7.0. The addition of the urine sample turned the blue ensemble yellow and altered the UV–vis absorption spectra. The ensemble exhibits excellent selectivity for inorganic phosphorus over other constituents of urine. We validate the accuracy of our method by the standard procedure (molybdenum blue assay for phosphate). The detection results are basically consistent with normal excretion of phosphate. Furthermore, we fabricated a new kind of inorganic phosphorus reagent kit, which enables us to inspect phosphate concentrations of urine with the naked eye. Fit for all kinds of various clinic uses, our reagent kit is a hopeful substitute for the molybdenum reagent kit.      

Fluorometric determination of sugars using fluorescein-labeled concanavalin A–glycogen conjugates

The fluorescence of fluoresceinisothiocyanate-labeled concanavalin A (FITC-Con A) was quenched by forming an FITC-Con A–glycogen conjugate and dequenched upon addition of sugars to the conjugate solution due to disaggregation of the conjugate. However, fluorescence quenching was barely observed upon formation of FITC-Con A–dextran conjugate. The sugar-induced fluorescence response of the FITC-Con A–glycogen conjugate depended significantly on the type of sugar: methylated α-D-glucose and α-D-mannose both induced high and rapid responses, while the responses to D-mannose and D-glucose were moderate. In contrast, no response was observed in the presence of D-galactose due to a lack of affinity to Con A. Thus, it is apparent that D-glucose and other sugars can be detected via the fluorescence of the FITC-Con A–glycogen conjugate.      

A new ICP–TOFMS. Measurement and readout of mass spectra with 30 μs time resolution, applied to in-torch LA–ICP–MS

In-torch LA–ICP–MS was implemented into an in-house-built ICP–TOFMS system. The fast data acquisition capabilities of the new configuration allowed simultaneous multi-element measurement and readout of in-torch LA–ICP–MS signals with 30 μs time resolution. The measurements confirmed previously observed fine structures of in-torch generated signals and provided new insights in the dynamic processes in the plasma on a microsecond time scale. The new setup is described in detail and first figures of merit are given. Figure Time dependent multi element signal after laser ablation in the torch of an ICP-TOFMS instrument     

Site-specific binding of chelerythrine and sanguinarine to single pyrimidine bulges in hairpin DNA

Spectrofluorometric titration, electrospray ionization time-of-flight mass spectrometric and UV melting methods were employed to study the binding of chelerythrine and sanguinarine to bulged DNA. The results showed that both alkaloids bind specifically to single pyrimidine (C, T) bulge sites. The ability of sanguinarine to bind to both regular and bulged hairpins was found to be stronger than that of chelerythrine, but the binding selectivity of chelerythrine toward single-base bulges was much larger than that of sanguinarine. Figure Association constants for chelerythrine and sanguinarine toward regular and single-base bulged hairpins obtained from fluorometric analysis     

Noninvasive methods for the investigation of ancient Chinese jades: an integrated analytical approach

This paper reports on an integrated analytical approach for the noninvasive characterization of Chinese nephrite samples, encompassing both geological reference specimens and museum objects. Natural variations induced by cationic substitutions, as well as human-induced alterations such as heating, which both affect color, are the focus of this contribution. Totally noninvasive methods of analysis were used, including X-ray fluorescence spectroscopy, Raman microspectroscopy, visible reflectance spectroscopy and X-ray diffraction; moreover, the feasibility of using a portable Raman spectrometer for the in-field identification of jades has been demonstrated. Fe/Fe+Mg (% p.f.u.) ratios of the jades have been calculated based on hydroxyl stretching Raman bands, which will provide an important addition to similar data that are being collected at major museums in the Western and Eastern hemispheres.      

Rapid response behavior,at room temperature,of a nanofiber-structured TiO<Subscript>2</Subscript> sensor to selected simulant chemical-warfare agents

A chemical prototype sensor was constructed based on nanofiber-structured TiO₂ and highly sensitive quartz resonators. The gas-sensing behavior of this new sensor to selected simulant warfare agents was investigated at room temperature. Results showed rapid response and good reversibility of this sensor when used with high-purity nitrogen. This provides a simple approach to preparation of materials needed as chemical sensors for selected organic volatiles or warfare agents. Figure Sensing behavior of TiO₂ nanofiber sensor to chemical vapors     

Feasibility of gamma irradiation as a stabilisation technique in the preparation of tissue reference materials for a range of shellfish toxins

The effect of γ-irradiation on concentrations of hydrophilic and lipophilic phycotoxins has been investigated by use of HPLC–UV and LC–MS. Pure toxins in organic solvents and toxins in mussel (Mytilus edulis) tissues were irradiated at three different doses. In solution all toxin concentrations were reduced to some extent. Most severe decreases were observed for domoic acid and yessotoxin, for which the smallest dose of irradiation led to almost complete destruction. For pectenotoxin-2 the decrease in concentration was less severe but still continuous with increasing dose. Azaspiracid-1 and okadaic acid were the least affected in solution. In shellfish tissue the decrease in toxin concentrations was much reduced compared with the effect in solution. After irradiation at the highest dose reductions in concentrations were between ca. 5 and 20% for the lipophilic toxins and there was no statistical difference between control and irradiated samples for azaspiracids in tissue. Irradiation of shellfish tissues contaminated with domoic acid led to a more continuous decrease in the amount of the toxin with increasing dose. The effect of irradiation on the viability of microbial activity in shellfish tissues was assessed by using total viable counting techniques. Microbial activity depended on the type of shellfish and on the pretreatment of the shellfish tissues (with or without heat treatment). As far as we are aware this is the first investigation of the effectiveness of irradiation as a technique for stabilising tissue reference materials for determination of phycotoxins. Our results suggest that this technique is not effective for materials containing domoic acid. It does, however, merit further investigation as a stabilisation procedure for preparation of shellfish tissue materials for some lipophilic toxins, in particular azaspiracids. Chemical structures of the toxins investigated in the study     

A new molecularly imprinted polymer for selective extraction of cotinine from urine samples by solid-phase extraction

Cotinine, the main metabolite of nicotine in human body, is widely used as a biomarker for assessment of direct or passive exposure to tobacco smoke. A method for molecularly imprinted solid-phase extraction (MISPE) of cotinine from human urine has been investigated. The molecularly imprinted polymer (MIP) with good selectivity and affinity for cotinine was synthesized using cotinine as the template molecule, methacrylic acid as the functional monomer, and ethylene glycol dimethacrylate as the cross-linker. The imprinted polymer was evaluated for use as a SPE sorbent, in tests with aqueous standards, by comparing recovery data obtained using the imprinted form of the polymer and a non-imprinted form (NIP). Extraction from the aqueous solutions resulted in more than 80% recovery. A range of linearity for cotinine between 0.05 and 5 μg mL⁻¹ was obtained by loading 1 mL blank urine samples spiked with cotinine at different concentrations in acetate buffer of pH 9.0, and by using double basic washing and acidic elution. The intra-day coefficient of variation (CV) was below 7% and inter-day CV was below 10%. This investigation has provided a reliable MISPE–HPLC method for determination of cotinine in human urine from both active smokers and passive smokers. Figure     

Quantitative biomarker assay with microfluidic paper-based analytical devices

This article describes the use of microfluidic paper-based analytical devices (μPADs) to perform quantitative chemical assays with internal standards. MicroPADs are well-suited for colorimetric biochemical assays; however, errors can be introduced from the background color of the paper due to batch difference and age, and from color measurement devices. To reduce errors from these sources, a series of standard analyte solutions and the sample solution are assayed on a single device with multiple detection zones simultaneously; an analyte concentration calibration curve can thus be established from the standards. Since the μPAD design allows the colorimetric measurements of the standards and the sample to be conducted simultaneously and under the same condition, errors from the above sources can be minimized. The analytical approach reported in this work shows that μPADs can perform quantitative chemical analysis at very low cost.      

On-column labeling for capillary electrophoretic analysis of individual mitochondria directly sampled from tissue cross sections

This technical note reports on a new procedure to on-column-label organelles sampled from a tissue cross section into a fused silica capillary. These organelles are then analyzed by capillary electrophoresis with postcolumn laser-induced fluorescence detection. In this procedure, the fluorescent label does not come in contact with the tissue, which facilitates visualization of the sampled tissue cross section. In addition, on-column labeling allows for better control of the reaction time and fluorescent label concentrations. As a proof-of-principle, we show results of mitochondria from rat gastrocnemius muscle cross sections that were on-column-labeled with 10-N-nonyl acridine orange (NAO), a mitochondrion-specific probe, and compare them with results for NAO in-tissue labeling of the same tissue. The new organelle labeling procedure reported here may easily be extended to the analysis of individual organelles in other biological samples and may become a valuable tool in studies investigating the role of mitochondria in muscle aging and exercise physiology.      

Electrophoresis microchips with sharp inlet tips, for contactless conductivity detection, fabricated by in-situ surface polymerization

A novel method based on in-situ surface polymerization of methyl methacrylate (MMA) has been developed for rapid fabrication of poly(methyl methacrylate) (PMMA) electrophoresis microchips with sharp inlet tips. Prepolymerized MMA containing an ultraviolet (UV) initiator was directly sandwiched between a nickel template and a PMMA plate. The image of the relief on the nickel template was precisely replicated in the synthesized PMMA layer on the surface of the commercially available PMMA plate during UV-initiated polymerization at room temperature. The chips were subsequently assembled by thermal bonding of channel plates and cover sheets. The sample was directly introduced into the separation channel through a sharp inlet tip, which was placed in the sample vial, without use of an injection cross. The attractive performance of the novel PMMA microchips has been demonstrated by using contactless conductivity detection for determination of several inorganic ions. Such rapid and simple sample introduction leads to highly reproducible signals with relative standard deviations of less than 5% for peak responses. These new approaches significantly simplify the process of fabricating PMMA devices and show great promise for high-speed microchip analysis.      

Nuclear magnetic resonance of mass-limited samples using small RF coils

Figure Schematic diagram of a typical arrangement used for hyphenating chemical microseparations (e.g. capillary HPLC, CE, or CEC) with microcoil NMR detection     

New near-infrared LIBS detection technique for sulfur

Sulfur has been detected in a spectral window (around 868 nm) previously unexplored by laser-induced breakdown spectrometry (LIBS), using an ablation laser with an ultraviolet wavelength, a gated detector, and inert ambient gas at a low, controlled pressure. This spectral window enables new-generation gated iCCD cameras to be used, which have adequate quantum efficiencies up to 900 nm. Application of our technique can substantially improve signal strength and thus extends the ability of LIBS to detect many nonmetallic elements.      

Methodology for rapid tritium determination in urine

Summary The present work proposes a methodology for a rapid determina-tion of the tritium content in urine. The urine is treated with active carbon and tritium is determined by liquid scintillation counting. Different kinds of active carbon were experimented for the metabolites removal from urine samples. The counting efficiency was calculated by a quench curve using yellow food dye as a quenching agent. It was obtained a procedure which maintained a good reproducibility, low uncertainty and detection limit of 7 Bq/l (10 ml of urine, 120 minutes of counting time and efficiency of 23.9%).     

Nanoscale organic and polymeric field-effect transistors as chemical sensors

This article reviews recently published work concerning improved understanding of, and advancements in, organic and polymer semiconductor vapor-phase chemical sensing. Thin-film transistor sensors ranging in size from hundreds of microns down to a few nanometers are discussed, with comparisons made of sensing responses recorded at these different channel-length scales. The vapor-sensing behavior of nanoscale organic transistors is different from that of large-scale devices, because electrical transport in a nanoscale organic thin-film transistor depends on its morphological structure and interface properties (for example injection barrier) which could be modulated by delivery of analyte. Materials used in nanoscale devices, for example nanoparticles, nanotubes, and nanowires, are also briefly summarized in an attempt to introduce other relevant nano-transducers.      

Further research on the photo-SPME of triclosan

In this study the photoinduced degradation of triclosan has been investigated by photo-solid-phase microextraction (photo-SPME). In photo-SPME, photodegradation is carried out on the SPME fibre containing the target compound. Triclosan was extracted from aqueous solutions by use of polydimethylsiloxane SPME fibres and these were subsequently exposed to UV irradiation (power 8 W, wavelength 254 nm) for different times (from 2 to 60 min). The photodegradation kinetics of triclosan were investigated, the photoproducts generated were tentatively identified, and the photochemical behaviour of these products was studied by use of this on-fibre approach followed by gas chromatographic–mass spectrometric analysis. Eight photoproducts were tentatively identified, including chlorinated phenols, chlorohydroxydiphenyl ethers, 2,8-dichlorodibenzo-p-dioxin, and a possible dichlorodibenzodioxin isomer or dichlorohydroxydibenzofuran. The main photodegradation mechanisms were postulated and photodegradation pathways proposed. The effect of pH on triclosan degradation and on triclosan-to-dioxin conversion was also investigated. Triclosan degradation occurred, and generation of 2,8-dichlorodibenzo-p-dioxin was confirmed, throughout the pH range studied (from 3 to 9).