A two-dimensionally imaging spectrometer system was employed to measure spatial emission images of a glow discharge plasma in atomic emission spectrometry. The emission intensities were not uniform in the radial direction of the plasma region, but yielded a characteristic distribution from the central portion towards the surrounding zone in the plasma. Temporal variations in the emission images were observed when a zinc-coated steel plate and a thermally-deposited copper film were employed as the sample. Depth profiles of these surface layers, estimated from the emission images, were compared among different integration areas of the emission intensities.

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Proteins labeled with a luminescent lanthanide chelate, {{2,2′,2″,2′′′-{4′-{[(4,6-dichloro-1,3,5-triazin-2-yl)amino]biphenyl-4-yl}-2,2′:6′,2″-terpyridine-6,6″-diyl}bis(methylenenitrilo)}tetrakis(acetato)}europium(III) (DTBTA-Eu³⁺),were analyzed with sodium dodecyl sulfate-polyacrylamide gel (SDS-PAGE) slab gel electrophoresis and hydroxyethyl cellurose gel capillary electrophoresis with a time-resolved fluorometric detector. The metal ion of the luminescent lanthanide chelate did not dissociate from the ligand during electrophoresis, and the luminescence was retained. On a slab gel, the band of DTBTA-Eu³⁺-labeled streptavidin was apparently less broad than that of AlexaFluor 488-labeled streptavidin. DTBTA-Eu³⁺ in SDS-PAGE slab gel is stable, and the gel after electrophoresis can be dried and stored for at least one year without luminescence fading. In capillary gel electrophoresis (CGE), five labeled proteins with different molecular weight were separated, and a good correlation was observed between the molecular weight and the migration time. Although the detection limits of these proteins determined in buffer solutions of the capillary electrophoresis were not better than those reported for CGE with laser-induced-detection, the detection limits of the same proteins in the present CGE system were not significantly deteriorated in serum solutions compared to those in buffer solutions, and the advantage of using time-resolved detection has been shown.

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Poly(ethylene oxide)-stabilized silver nanoparticles (PEO-SSNPs) were synthesized and investigated for their potential use in capillary electrophoretic separation of proteins. It was found that the PEO-SSNPs were relatively stable against changes of the buffer ionic strength, while they began to aggregate with increase of buffer pH. Adding 0.024 g/L PEO-SSNPs to 30 mmol/L phosphate buffer (pH 2.66) led to obvious increase in the peak heights of albumin bovine and albumin egg. Also, the separation efficiency for all the standards enhanced due to the suppressed wall-adsorption of proteins in the presence of the nanoparticles. The above experiments suggest that the PEO-SSNPs are effective pseudostationary phase for CE separation of proteins.

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In this paper, we describe systematic detailed considerations of the feasibility of using various metal nanoparticles for organic-matrix-free surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS). In order to avoid the influence of organic molecules on the nanoparticles, stabilizer-free bare nanoparticles of Ag, Au, Cu and Pt were prepared by laser ablation. Although all metal nanoparticles absorbed N₂ laser light (337 nm) energy, the performance of desorption/ionization of a representative peptide, angiotensin I, strongly depended on the metal element. Citrate buffer was used as a proton source; it reduced the amount of alkali cation adducts present. Then, protonated molecules of analytes predominated in the mass spectra when Au and Pt nanoparticles were used. Pt nanoparticles showed the highest performance in SALDI-MS, owing to their smaller heat conductivity and higher melting temperature. The selective desorption of a cationic surfactant with longer alkyl chains and a peptide with methionine was also observed.

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We have reported on a novel enzyme immunoassay method for the detection of protein using biocatalytic silver nanoparticles as an enhanced substrate based on surface-enhanced Raman scattering (SERS). First, ascorbic acid was converted from ascorbic acid 2-phosphate by alkaline phosphatase immobilized on polystyrene microwells after a typical sandwich immunoreaction. Then Ag(I) ions were reduced to silver nanoparticles by the obtained ascorbic acid, which would result in a SERS signal when Raman dyes were absorbed. Using human IgG as a model protein, a wide linear dynamic range (1 to 100 ng ml^-1) was reached with a low detection limit (0.02 ng ml^-1) under the optimized assay conditions. Moreover, the production of an enhanced substrate was chosen as the signaling element in this method, which demonstrates a new way for SERS-based quantitative detection. These results suggest that the application of SERS enhanced by biocatalytic production of metal nanopaticles holds a promising potential for a sensitive immunoassay.

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The concentration level of L-glutamate released from the region CA1 of mouse hippocampal slices under tetraethylammonium chloride (TEA) stimulation was measured by two independent methods, i.e., a glass capillary-based enzyme sensor and a patch sensor, and compared with each other for different slice preparations. In a submerged slice preparation, the sensors were positioned in bath solutions several tens µm above CA1, respectively. The sensors exhibited almost the same level of extra-slice L-glutamate concentration. When a capillary sensor was implanted in region CA1 at a depth of approximately 10 µm, the TEA-induced L-glutamate release pattern was very similar to those observed with the capillary sensor in a bath use. The concentration level of intra-slice (extracellular) L-glutamate was found to be in the range from 6 to 10 µM, which was significantly larger than that of the extra-slice one. These results demonstrate that L-glutamate released from each neuronal region inevitably diffuses out of the slices, and the extra-slice L-glutamate level reflects the extracellular one.

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A new complex, manganese(II) azide complex with N-methylimidazole, has been synthesized and characterized by elemental analysis, IR spectra and single crystal X-ray studies. Absorption spectroscopy, emission spectroscopy, viscosity measurements and CD spectroscopy have been used to investigate the binding of the complex with calf thymus DNA (CTDNA). The intrinsic binding constant K_b of the complex with DNA was obtained by electronic absorption titration; the value is consistent with the result by fluorescence titration method. The spectroscopic studies together with viscosity measurements support the claim that the title complex bonds to CT-DNA by a groove mode. Control cleavage experiments using pBR 322 plasmid DNA which suggest minor groove binding for the complex.

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New PVC membrane electrodes for the determination of sulfadiazine (SDZ) are presented. The electrodes are fabricated with conventional and tubular configurations with a graphite-based electrical contact, and no internal reference solution. The selective membranes consist of bis(triphenylphosphoranilidene)ammonium·SDZ (electrode A), tetraoctylammonium bromide (electrode B), or iron(II)-phthalocyanine (FePC) (electrode C) electroactive materials dispersed in a PVC matrix of o-nitrophenyl octyl ether (o-NPOE) plasticizer. The sensors A, B, and C displayed linear responses over the concentration ranges 1.0 × 10^-2 - 1.0 × 10^-5, 1.0 × 10^-2 - 7.5 × 10^-6, and 3.2 × 10^-2 - 7.0 × 10^-6 mol l^-1 (detection limits of 1.09, 2.04 and 0.87 µg ml^-1) with anionic slopes of -57.3 ± 0.1, -46.7 ± 0.5, and -65.1 ± 0.2 mV decade^-1, respectively. No effect from pH was observed within 4.0 - 5.5, 4.8 - 10, and 4.5 - 8, respectively, and good selectivity was found. The sensors were applied to the analysis of pharmaceuticals and biological fluids in steady state and in flow conditions.

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The redox processes of quercetin in acidic medium (pH 1.8) were investigated on a graphite-wax electrode by cyclic voltammetry, potential-controlled UV/Vis spectra and derivative cyclic voltabsorptometry. A long-optical-path thin-layer cell was used for the spectroelectrochemical measurements. A stable quinonic product with a united conjugated structure was found to form at the first anodic peak or higher potentials via an EC mechanism, and was non-electroactive unless oxygen evolution potential was reached. Quercetin both in the free solution and pre-adsorbed on electrodes participated in the reaction at the first anodic peak, and the contribution of species in solution to total current was estimated. The subsequent anodic peaks as well as all the cathodic peaks were adsorption waves corresponding to the further redox of the adsorbed intermediates. The results demonstrate that cyclic voltabsorptometry in a long-optical-path cell is a feasible method for the analysis of electrochemical processes coupled with adsorption and homogeneous chemical transitions.

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Ion-exclusion chromatography was examined for the simultaneous spectrophotometric determinations of orthophosphate and silicate ions in river water using an ascorbate solution as both an eluent and a reducing agent, followed by postcolumn derivatization using molybdate. The detector responses for both ions increased with increased ascorbic acid concentration in the eluent, but peak tailing was observed for the orthophosphate ion. This suggests that the amounts of undissociated orthophosphate ions increased with decreased eluent pH, resulting in the penetration of the phosphate to the Donnan's membrane formed on the resin surface. Using a neutral sodium ascorbate solution as an eluent, the peak shape was improved. With optimized separation and derivatization conditions (eluent, 20 mM sodium ascorbate; color-forming reagent, 10 mM sodium molybdate-60 mM sulfuric acid; flow rates of eluent and color-forming reagent, 0.4 and 0.2 mL min^-1; coil length, 6 m), the detection limits of orthophosphate and silicate ions were 0.9 and 1.0 µg L^-1, respectively. This method was successfully applied to the determination of orthophosphate and silicate ions in Kurose River water and the quantitative evaluations of the effects of water intake to a reservoir and discharge from a biological sewage treatment plant on the fluxes of these ions in the river.

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An HPLC method using fluorescence detection for the quantitation of curcuminoids, such as curcumin (C), demethoxycurcumin (DMC), and bisdemethoxycurcumin (BDMC) in turmeric products is described. This method involves a simple ultrasonic extraction with methanol as a pretreatment of turmeric products. The separation of curcuminoids and 2,5-xylenol (internal standard) was achieved within 30 min on a Cadenza CD-C₁₈ column (250 × 4.6 mm; i.d., 3 µm) with a mixture of acetate buffer and CH₃CN. The calibration curves of standard curcuminoids showed good linearities of more than 0.993 of the correlation coefficient. The instrumental detection limits for C, DMC and BDMC (signal-to-noise ratio = 3) were 1.5, 0.9 and 0.09 ng mL^-1, respectively. The relative standard deviations of intra-and inter-day assays by curcuminoids spiked to turmeric powder were less than 6.1%. The proposed method was successfully applied to determine curcuminoids in commercial turmeric products, such as turmeric powders, a tablet, a dressing, a beverage, tea, and crude drugs.

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A sensitive and rapid flow-injection analysis was developed for the determination of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC·HCl), which was used for the formation of amide (peptide) and esters as a dehydration or condensation reagent. The EDC·HCl could be determined by the flow-injection analysis based on a specific condensation reaction between malonic acid and ethylenediamine in aquatic media. The reaction was accelerated at 60°C, and the absorbance of the product was detected at 262 nm. The calibration graph of EDC·HCl showed good linearity in the range from 0 to 0.1% (0 to 0.0005 M), whose regression equation was y = 1.52 × 10⁹x (y, peak area; x, % concentration of EDC·HCl). The proposed method allowed high-throughput analysis; the sample throughput was 12 samples per hour. The limit of detection (LOD) and the relative standard deviation (RSD) were 2 × 10^-6 M and 1.0%, respectively. This reaction is proceeded in aqueous solution and specific for EDC·HCl.

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A simple and rapid flow-injection method is reported for the determination of dithiocarbamate fungicides (maneb, nabam and thiram) based on chemiluminescence detection. The method involves the photodegradation of dithiocarbamate fungicides via UV light in an alkaline medium. Photoproducts are then reacted with luminol in the absence of an oxidant. Linear calibration graphs were obtained in the range 0.01 - 4.0 mg L^-1 for maneb and nabam and 0.05 - 1.0 mg L^-1 for thiram with relative standard deviations (n = 4) in the range 1.0 - 2.6%. The detection limits (S/N = 3) of maneb, nabam and thiram were 10, 8.0 and 5.0 ng mL^-1, respectively, with a sample throughput of 100 h^-1. The method was successfully applied to determine these dithiocarbamate fungicides in spiked natural water samples.

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A flow injection chemiluminescent (FI-CL) method was developed for the determination of pioglitazone HCl. It is based on the sensitizing effect of the drug on the oxidation reaction of sulfite with cerium(IV). The different experimental parameters affecting the chemiluminescence intensity, such as concentration of reagents and some physical parameters of the manifold, were carefully studied and incorporated into the procedure. The method permits the determination of 0.05 - 3.0 µg ml^-1 of pioglitazone HCl with correlation coefficient r = 0.9999. The lower limit of detection (LOD) is 0.01 µg ml^-1 (S/N = 2) and the lower limit of quantitation (LOQ) is 0.05 µg ml^-1. The proposed method was compared with other reported methods and was found to be equally accurate and precise. It was successfully applied to the determination of the drug in pharmaceutical preparations and in biological fluids.

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A simple and rapid flow-injection method is reported for the determination of retinol, its derivatives and α-tocopherol by its enhancement effect on a potassium permanganate-formaldehyde chemiluminescence system in an acidic medium. Linear calibration graphs were obtained between 5.0 × 10^-8 to 5.0 × 10^-6 mol L^-1 for all-trans-retinol, 5.0 × 10.8 - 2.5 × 10^-6 mol L^-1 for all-trans-retinal, 5.0 × 10^-7 - 1.0 × 10.5 mol L^-1 for retinoic acid, 1.0 × 10^-7 - 5.0 × 10^-6 mol L^-1 for retinyl acetate and retinyl palmitate and 1.0 × 10^-8 - 5.0 × 10^-6 for α-tocopherol, with relative standard deviations (RSD; n = 4) in the range of 0.8 - 2.8%. The limits of detection (S/N = 3) were in the range of 5.0 × 10^-9 - 1.0 × 10^-7 mol L^-1 with a sample throughput of 100 h^-1. The influence of common ions, excipients in pharmaceutical preparations and related organic compounds were studied on the determination of retinol and α-tocopherol individually. The method was applied to determine retinol and α-tocopherol in pharmaceutical preparations, and the results obtained were in reasonable agreement with the amount labelled.

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The kinetic parameters of gold(III) sorption by unloaded polyurethane foams (PUFs) and PUFs impregnated with some onium cations e.g. tetramethylammonium perchlorate (TMA⁺ClO₄^-), tetrabutylammonium iodide (TBA⁺I^-), and tetraheptylammonium bromide (THA⁺Br^-), have been determined. The retention steps were found to be fast, reached equilibrium in a few minutes and followed a first-order rate equation with an overall rate constant, k, of 0.0076 and 0.007 min^-1, respectively. The thermodynamic characteristics of gold(III) retention by the unloaded PUFs and THA⁺Br^- immobilized PUFs have been critically studied. The negative values of ΔH and ΔS are interpreted as the exothermic and spontaneous reaction of gold(III) sorption onto unloaded PUFs and foams impregnated with THA⁺Br^-. The cellular structure of the PUFs sorbent offer unique advantages over conventional bulk-type sorbents in the rapid, versatile effective separation and/or preconcentration of gold ions.

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A module was developed for the continuous monitoring of volatile halogen organic pollutants in complex matrices. The module utilized a polymer membrane for extraction and a capillary gas chromatography-mass spectrometry (GC-MS) for detection. The extraction of analytes (CHCl₃, CHCl₂Br, CHClBr₂ and CHBr₃) from samples was performed in a flow system mediated by a non-porous flat membrane. The effects of the phase-volume ratios, flow conditions, kinetics, analyte properties and matrices were assessed and optimized. The limits of detection were at low µg L^-1 to ng L^-1 levels, with GC-MS analysis under selected ion monitoring (SIM), whereas enrichment factors between 6 and 30 were achieved. Precision values calculated as repeatability and reproducibility with a relative standard deviation (%RSD, n = 5) of 7.2 to 9.5 after 30 min were obtained. The performance of the continuous membrane assisted solvent extraction system was compared with classical liquid-liquid extraction. The method was applied to the extraction of trihalomethanes in chlorinated drinking-water samples.

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A simultaneous determination method of trace amounts of perfluorinated compounds, such as perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) in packaging materials and textiles, has been developed, using pressurized liquid extraction (PLE) with gas chromatography-mass spectrometry (GC/MS). The perfluorinated compounds were primarily extracted from the samples by a PLE procedure, in which the parameters were optimized by response surface methodology. The solvent was then removed by blowing nitrogen and a silylation step was carried out with N,N-bis(trimethylsilyl)trifluoroacetamide. The silylated compounds were identified and quantified by GC/MS. The proposed method was applied to determine the PFOA and PFOS in polytetrafluoroethylene packaging materials and textiles, where the detection limits of the two compounds were 1.6 and 13.9 ng mL^-1, respectively. The results showed that the concentrations of PFOA and PFOS in the packaging materials and textiles ranged from 17.5 to 45.9 and 33.7 to 81.3 ng g^-1, respectively.

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A known principle in which triphenylphosphine is allowed to be oxidized by hydroperoxides to triphenylphosphine oxide, was developed into an analytical method for determination of hydroperoxide content in light mineral oils using GCMS-detection and quantification. By suitable choice of reagent solution solvents and internal standard, the method proved to be simple to apply and very rugged. For a series of oven-aged oil samples the developed method gave results with a satisfactory correlation to an established iodometric method (which also gave a higher standard deviation). A mechanistic explanation for interference of high concentrations of added aldehydes on measurements was also suggested, but it was found that the interference is of no practical consequence for oxidized oil samples.

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Natural monocrystalline pyrite as a new indicator electrode for the potentiometric titration of weak acids in acetonitrile, propionitrile and benzonitrile was studied. The investigated electrode showed a linear dynamic response for p-toluenesulfonic acid concentrations in the range from 0.1 to 0.001 M, with a Nernstian slope of 74 mV per decade. Sodium methylate, potassium hydroxide and tetrabutylammonium hydroxide (TBAH) proved to be very suitable titrating agent for this titration. The response time was less than (11 s) and the lifetime of the electrode is long. The advantages of the electrode are log-term stability, fast response, and reproducibility, while the sensor is easy to prepare and of low cost.

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An alternative process for the design and construction of fluidic devices is presented. Several sealing processes were studied, as well as the hydrodynamic characteristics of the proposed fluidic devices. Manifolds were imprinted on polymeric substrates by direct-write milling, according to Computer Assisted Design (CAD) data. Poly(methyl methacrylate) (PMMA) was used as substrate due to its physical and chemical properties. Different bonding approaches for the imprinted channels were evaluated and UV-photopolymerization of acrylic acid (AA) was selected. The hydrodynamic characteristics of the proposed flow devices were assessed and compared to those obtained in similar flow systems using PTFE reactors and micro-pumps as propulsion units (multi-pumping approach). The applicability of the imprinted reactors was evaluated in the sequential determination of calcium and magnesium in water samples. Results obtained were in good agreement with those obtained by the reference procedure.

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A new C₃-functionalized cyclotriveratrylene (CTV) bearing three fluorogenic quinolinyl groups was synthesized and studied as a fluorescent probe. The CTV derivative exhibited a selective response of fluorescence enhancement toward Cu²⁺. The fluorescence intensity in CH₃CN was increased until the [Cu²⁺]/[CTV derivative] mole ratio was 3. Moreover, C₃-functionalized CTV(2-quinolinemethyl)₃ was applied to a visible fluorescent probe by using a plasticized polymeric membrane. The emission profile was observed by a fluorescence microscope after immersing the membrane in a 1 × 10^-5 M aqueous solution of Cu²⁺.

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A practical analytical method was developed for the routine analysis of perchlorate in environmental and drinking-water samples by liquid chromatography-electrospray ionization mass spectrometry (LC/ESI-MS) using an anion exchange column. By using ¹⁸O-enriched perchlorate as an internal standard, the limits of quantification of perchlorate determined by tenfold of the signal-to-noise ratio and tenfold of the standard deviation were 0.1 and 0.03 µg L^-1, respectively. The perchlorate concentrations in the raw and finished water samples from seven water purification plants were determined by LC/ESI-MS. Perchlorate was detected in 12 out of 13 samples, and the perchlorate concentrations in the samples were from 0.1 to 36.1 µg L^-1.

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We present here the results of applying a membrane method to terahertz (THz) transmittance spectroscopy of amino acids. Two kinds of amino acids dissolved in water or bovine serum were dropped and dried on polymer membranes. Absorbance spectra of the membranes were obtained with a GaP THz spectrometer. The frequency range was 0.6 - 6.0 THz and the line width was 3 GHz. Characteristic absorption peaks attributable to the amino acids were observed with membranes made of suitable materials.

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