The determination of rare earth elements (REEs) in airborne particulate matter (APM) was conducted, and the distribution pattern of atmospheric REEs was evaluated in this study. The APM was collected in the center of Tokyo, Japan, where serious air pollution is always of concern. A cellulose acetate membrane filter was used to collect the APM because Ba and REEs contamination is lower than that in a quartz glass fiber filter. The REEs measurement was conducted by ICP-MS after the digestion of the APM by a microwave acid digestion procedure. The standard reference material (SRM) of NIST 1648 urban particulate matter was used to validate the accuracy of the analytical method. The analytical results for SRM well agreed with those of the reference and reported values. Consequently, the analytical method established in this study was applied to the determination of REEs in APM collected in Tokyo, Japan. The obtained REEs distribution pattern in the APM showed a positive anomaly of Tb and Eu. The La/Sm ratio, which is considered to be as a good indicator of the anthropogenic effect, in size-classified APM showed a high degree of the anthropogenic effect in fine APM with a diameter of <1.1 μm. Emission sources of Tb, Eu and other REEs are discussed.
The retention behavior on poly(oxyethylene) (POE) chemically-bonded stationary phases was investigated in ion-exchange, reversed-phase (RP) and hydrophilic interaction (HILIC) modes in capillary liquid chromatography. The eluent cations fixed on the oxygen atoms of the POE chains by ion-dipole interaction worked as the anion-exchange sites for the separation of inorganic anions. Nonpolar analytes were retained on the POE stationary phases in the RP mode, while polar organic analytes were retained in the HILIC mode. Sodium alkyl sulfate dynamically modified on the stationary phase enhanced the hydrophobic property of the stationary phase. The effect of the oxyethylene unit number on the retention behavior was examined, and it was expected that the eluent cation is trapped among multiple POE chains by ion-dipole interaction.
A sulfated poly β-cyclodextrin (SPCD) modified silica-based monolithic column was prepared for enantiomeric separation. First, 2-hydroxy-3-allyloxy-propyl-β-cyclodextrin (allyl-β-CD) was bonded onto a bifunctional reagent 3-(methacryloxy)propyltriethoxysilane (γ-MAPS) modified silica-based monolith through radical polymerization; the column was then sulfated with chlorosulfonic acid. The SPCD chiral stationary phase resolved the boring problem associated with desalting when sulfated CDs were synthesized to act as chiral additives. The inorganic salt in the column introduced during the sulfating process could be easily removed by washing the column with water for some time. Chiral compounds investigated were successfully resolved into their enantiomers on the SPCD modified monolith in the capillary electrochromatography (CEC) mode. Due to the existence of the −SO3H group, electrosmotic flow (EOF) was obviously increased, and all of the separations could be carried out in 20 min with only a minor loss in the column efficiency and resolution.
The response curves and sensor properties of silver-deposited optical fibers with Ag film thicknesses of 20.0 − 80.0 nm based on surface plasmon resonance (SPR) were investigated. The response of the Ag-deposited optical fiber sensor depends on the thickness of the Ag film. The Ag-deposited optical fiber sensors show higher responses than those deposited with Au. The reflection properties of Ag films with thicknesses of 30.5 − 70.2 nm due to the SPR phenomenon were also measured and considered. The surfaces of these Ag films consist of various spherical grains with diameters of 30 − 90 nm and the surface height distribution is almost random, having a value of more than 8 nm. X-ray photoelectron spectroscopy (XPS) showed the presence of very thin (0.3 nm) native oxide layers on the Ag films. The Ag-deposited optical fiber sensor exhibited no change in the sensor properties following prolonged use for 4 months. The response curves of the Ag-deposited optical fiber sensors by use of SPR theoretical equations were calculated and compared with those obtained by experimentation.
A simple method was found for the fabrication of silver nanosheets (AgNS) by the catalysis of gold nanoparticles (AuNP) on an amine-terminated cubic boron nitride (cBN) surface deposited on a Si(001) substrate in the presence of reductant. The morphology of the AgNS/AuNP/NH2-cBN/Si(001) sample was characterized by scanning electron microscopy and X-ray diffraction. The performance of the AgNS/AuNP/NH2-cBN/Si(001) sample as surface-enhanced Raman scattering (SERS) active substrate was evaluated by using 4-aminothiophenol (PATP) as the probe molecule. The SERS measurements showed that the maximum intensity was obtained on the AgNS/AuNP/NH2-cBN/Si(001) sample for 5 min silver deposition. Compared with the AuNP/NH2-cBN/Si(001) sample and a silver film/cBN/Si(001) prepared by the mirror reaction, the SERS signal of PATP was obviously improved on the above AgNS/AuNP/NH2-cBN/Si(001) film. The sensitivity and the stability of the AgNS/AuNP/NH2-cBN/Si(001) sample were also investigated.
Solid-phase spectrophotometry has been improved for the determination of the total and dissolved phosphate in water. The target phosphate-P at sub-μg dm−3 to μg dm−3 levels in a 20-cm3 water sample was concentrated as the molybdenum blue species to 0.06 or 0.12 cm3 using a Sephadex G-25 within 30 min, and gel beads were introduced to a 1.5-mm or 3-mm diameter flow cell having a 10-mm light path length. To minimize the error caused by any difference in the packing state of the gel beads in the cell for each measurement, the absorbances of the blue color were directly measured at 836 nm and at 450 nm using a UV-visible spectrophotometer. The absorbance difference (ΔA) of the two wavelengths was used for determining the trace amounts of P. The sensitivity achieved by this procedure was higher by a factor of over 100 for a 20-cm3 sample compared to that of the corresponding solution method using a 10-mm cell, and the detection limit was as low as 0.1 μg dm−3. Higher sensitivity was obtained using 100 cm3 water samples. Trace levels of the total and dissolved phosphate at sub-μg dm−3 to μg dm−3 levels in samples from mountainous small streams were directly determined without any preconcentration procedures.
We have developed an analysis system for photocatalytic reactions, which utilizes a TiO2 immobilized micro-capillary and a detection technique for dye concentration at arbitrary positions. In this study, we investigated the reaction processes for the photocatalytic decomposition of rhodamine 6G. This system allows the distinction of direct and secondary photocatalytic reactions under the same experimental conditions. The direct reaction occurs between adsorbed species and photoexcited electrons or holes, while the secondary reaction is induced by radicals, such as ·OH, O2+·, generated in water or ethanol. The entire reaction was studied by monitoring the dye concentration in the UV irradiated area, while only the secondary reaction was monitored outside the UV irradiated area.
In the present work, a new ligandless-ultrasound-assisted emulsification microextraction (LL-USAEME) method was developed for preconcentration trace amounts of nickel as a prior step to its determination by flame atomic absorption spectrometry. Some factors influencing the extraction efficiency of nickel and its subsequent determination were studied and optimized, such as type and volume of the extraction solvent, pH, extraction time, extraction temperature and ionic strength. Under the optimal conditions, the calibration curve was linear over the range of 1.0 ng mL−1 – 1.0 μg mL−1 for nickel with R2 = 0.9997. The detection limit was 0.34 ng mL−1 in the original solution (3Sb/m) and the relative standard deviation for 8 replicate determination of 0.3 μg mL−1 nickel was ±1.6%. The proposed method was successfully applied in the analysis of four real environmental water samples and good spiked recoveries over the range of 97 – 103% were obtained.
To characterize the pathway of ceftriaxone penetration into intervertebral discs, rat-tail discs were collected and immersed in a ceftriaxone solution for an in vitro study. For this in vivo experiment, plasma and tail discs were collected 30 min after ceftriaxone administration (463.2 mg/kg, equal to 500 mg/kg disodium salt, iv). The ceftriaxone levels in the plasma and discs were determined with HPLC by a reversed-phase C18 column and a mobile phase of methanol and a 10 mM K2HPO4 solution (pH 6.7) (21:79, v/v). The results indicate that ceftriaxone was undetectable by the in vitro model. The concentrations of ceftriaxone in plasma and in intervertebral discs were 147.4 ± 21.2 and 4.0 ± 1.7 μg/mL (as disodium salt), respectively. Our results suggest that a sufficient blood supply is required for the passive diffusion of ceftriaxone into intervertebral discs. The concentration ratio of ceftriaxone in intervertebral disc-to-plasma was about 2.7% at 30 min after ceftriaxone disodium administration (500 mg/kg, iv).
The output signal generated by detectors used in ion mobility spectrometry (IMS) is a time-dependent, small ionic current. To be able to take full advantage of information contained in this signal, adequate procedures of signal processing need to be utilized. Methods of spectrum filtration, peak separation, base-line correction as well as one- and two-dimensional integration applied in quantitative analysis are described. The effectiveness of the chosen methods was demonstrated on examples of experimental results obtained by IMS. Measurements were performed for spectra of reactant ions and sample ions generated by acetone, methyl tert-butyl ether (MTBE), dimethyl methylphosphonate (DMMP) and benzene. It was demonstrated that the proposed methods considerably improve the quality of the spectra, increase the selectivity of detection and reduce the uncertainty of quantitative measurements.
An electrodeposited palladium and iridium/gold mixture has been investigated as a chemical modifier for mercury determination in environmental samples by solid sampling electrothermal atomic absorption spectrometry. Electrochemical procedures of platform surface modification performed in a cell with 20 ml of solution, and in a drop of modifier solution have been optimized. Simple electrolysis in a drop was found to be the most consistent, taking the reproducibility as the major criterion. A total mass of 250 μg of electrodeposited palladium or an iridium/gold mixture was used. The lifetime of 60 – 70 firings for a deposited iridium/gold mixture was smaller than that for palladium with a lifetime of 100 – 120 firings. The detection limit was 120 pg Hg. Different sample masses of between 0.1 and 10 mg were weighed into modified platforms according to the mercury content. The results obtained for mercury in environmental samples as soils, sediments and plant, using solid sampling and calibration against aqueous standards stabilized by potassium permanganate, were in good agreement with those achieved by using the thermal deposition of modifiers and with measurements by pyrolysis atomic absorption spectrometry with gold amalgamation.
A simple amperometric detection (AD) method based on mesoporous platinum (Pt) electrodes has been developed for the determination of sugars (glucose, fructose, and sucrose) with high-performance anion-exchange chromatography (HPAEC). The amperometric detection is based on the direct oxidation of sugars on mesoporous Pt films formed on a gold electrode. The mesoporous Pt electrode (roughness factor of 243) sensitively responded to glucose, fructose, and sucrose in 80 mM sodium hydroxide solution as an alkaline mobile-phase for HPAEC. Under the optimum conditions, the limits of detection (S/N = 3) in these sugars were 0.24, 0.29, and 1.8 mM, for glucose, fructose, and sucrose, respectively. The reproducibility (relative standard deviation) of the measurements was less than 3.5%. The present method was applied to the determination of sugars in apple juice. The recoveries for all sugars ranged from 97 to 99%.
A capacitive sensing method based on a CuS ultrathin film modified electrode prepared by a surface sol-gel technique has been developed for the direct detection of human IgA. The resulting CuS film was investigated with cyclic voltammetry (CV), impedance spectroscopy, and quartz crystal microbalance (QCM). CV and impedance examinations showed that the CuS film formed on the gold electrode surface was insulated, and was applicable to form an insulating layer of a capacitive immunosensor. With QCM measurements, the thickness of the CuS film was evaluated to be 5.8 nm. The capacitance change was greatly increased by a CuS nanofilm-based immunosensor, which was initiated by the recognition of an immobilized antibody and the target antigen. The capacitance of the immunosensor corresponding to the concentration of human IgA was investigated by potentiostatic-step measurements. A linear calibration curve was obtained in the range of 1.81 – 90.5 ng ml−1 with a detection limit of 1.81 ng ml−1. There were no obvious interferences from the nonspecific adsorption of other proteins. With nice reproducibility and regeneration capacity, the CuS ultrathin film modified immunosensor could be used for the detection of human IgA in serum samples with a recovery of 96.1 – 104.4%, showing its promising applicability and reliability.
We have developed an accurate and traceable quantitation method of proteins and peptides by isotope-dilution mass spectrometry with the precolumn derivatization for hydrolyzed amino acid. This method utilized N-butylnicotinic acid N-hydroxysuccinimide ester iodide as the derivatization reagent and C-30 reversed phase column for the separation. Quantitative results of porcine insulin and human serum albumin obtained from the hydrolyzed six or seven amino acids showed a good agreement, with less than 3% of the expanded uncertainties. This method allows more accurate and more robust amino acid analysis in comparison with non-labeled methods.
Surface derivatization of Kevlar, poly(p-phenylene terephthalamide), fiber has been studied along with the evaluation of the surface characteristics of the chemically-modified fiber as the stationary phase in packed-capillary gas chromatography (GC). Several experimental parameters in the derivatization reaction have been optimized, and the retention behavior of the surface-derivatized fibrous stationary phase has been investigated using various standard solutes, such as alkanes, alcohols and alkylbenzenes. By introducing aminoethyl functional groups onto the surface of the fibrous material, a specific selectivity for polar solutes has been observed.