We have developed a highly stable supported liquid membrane based on ionic liquids (ILs) for the separation of rare-earth metals, employing N,N-dioctyldiglycol amic acid as a mobile carrier. The quantitative transport of Y and Eu through the membrane was successfully attained, and separation from metal impurities, Zn, was efficiently accomplished. A membrane stable enough for long-term operation was constructible from imidazolium-based ILs having a longer alkyl chain, such as octyl or dodecyl groups in an imidazolium cation.
To assay lipopolysaccharides (LPSs) in solutions containing Limulus amebocyte lysate (LAL)-inhibiting or LAL-enhancing compounds, we developed a selective endotoxin (LPS) assay using poly(ε-lysine)-immobilized cellulose beads (PL-Cellufine) and LAL. The PL-Cellufine can adsorb LPSs in a solution containing certain compounds (NaCl, proteins and amino acids) at an ionic strength of μ = 0.05 − 0.4 at neutral pH. The LPSs adsorbed on the PL-Cellufine were separated from the compounds by centrifugation and then the PL-Cellufine was suspended in LPS-free water. The LPS activities of the suspension are directly assayed by a turbidimetric time assay with the LAL reagent. The accuracy of the adsorption method was high compared with those of common solution methods. As for the common method, the apparent recovery of LPS from the compounds was 40 − 95%. This suggests that these compounds inhibit the LAL procedure. By contrast, the adsorption method showed good LPS recovery (88 − 120%) in all cases, without being inhibited or enhanced by the compounds.
This paper describes the preparation and characterization of an optical pH-sensing device using a H+-responsive fluoroionophore based on boron-dipyrromethene, immobilized to a mesoporous silica thin film. The fluoroionophore substituted with a silane coupling agent (KBH-01-Si) was successfully synthesized, and a mesoporous silica thin film was fabricated by the evaporation-induced-self-assembly (EISA) process. A pH optode was fabricated by attaching KBH-01-Si to the mesoporous silica thin film by covalent bonding via a sol-gel grafting method. The resulting pH optode shows single-excitation, dual-emission ratiometric response in aqueous buffer solutions of varying pH values. The sensor response was found to be reversible in the pH range from below 0.8 to 4.2, and showed good repeatability. The response times for a 95% signal change (t95%) were calculated to be 27 ± 2 s (n = 5) for a sample change from pH 4.0 to 1.0, and 23 ± 2 s (n = 5) for reverse change from pH 1.0 to 4.0. These results indicate that the novel pH optode allows for accurate and rapid measurements of pH values.
Emission spectra of constituent gas species from glow discharge plasmas using argon–helium, krypton–helium, argon–krypton, and krypton–argon gas mixtures were analyzed to elucidate collisional energy transfer between these gas species occurring in the plasma. In the argon–helium mixed gas plasma, the enhancement or quenching of particular Ar II lines was observed when helium was added to an argon-matrix glow discharge plasma, meaning that a redistribution in the population among the excited levels could be induced through argon–helium collisions. On the other hand, the krypton–helium plasma showed little change in the emission intensities of Kr II lines when helium was added to a krypton-matrix glow discharge plasma, meaning that energy exchanges between krypton and helium excited species occur inactively. These phenomena are principally because the excitation energy as well as the spin multiplicity between collision partners follow both the energy resonance conditions and the spin conservation rule in collisions of the second kind in the argon–helium system, but not in the krypton–helium system. In the argon–krypton and krypton–argon mixed gas plasmas, significant intensity changes of particular Ar II or Kr II lines could not be found; therefore, there were no dominant channels for energy exchanges between argon and krypton species in the mixed gas plasmas.
We have prepared polyethylene glycol (PEG)-type, polymer-based monolithic columns (PEG-type columns) to study the basic properties of PEG-type monolithic polymers. Chromatographic characteristics of the PEG-type columns were obtained using a semi-micro HPLC system while polycyclic aromatic hydrocarbons and benzene derivatives having various functional groups were utilized as solutes. Results were compared with those of commercially available polymer-based packed columns. PEG-type columns showed greater recognition ability for planar solutes based on separation factors, α (k triphenylene/ko-terphenyl) and α (k pyrene/k naphthalene). Benzene derivatives having a carboxyl group or a phenolic hydroxyl group, i.e., benzoic acid and phenol, tended to be retained more preferentially on the PEG-type column than other solutes without a carboxyl group or a phenolic hydroxyl group. These recognition abilities towards carboxyl group and/or phenolic hydroxyl group were found to be greater on the PEG-type columns having the longer ethylene oxide chains. However, unexpectedly HILIC mode did not work, even in 95% AN mobile phase, for nucleic-acid bases, benzoic acid, or phenol that careful studies suggested hydrophobic interaction was the dominant retention mechanism, while relatively weak hydrogen bonding between proton on carboxyl group or phenolic hydroxyl group of the retained solutes and oxygen in ethylene oxide chain on the PEG-based polymer prolonged the hydrophobic-based retentions.
A method has been developed for the measurement of transport activities in membrane vesicles obtained from human multidrug resistance-associated protein 3-expressing Sf9 cells for 1β-hydroxy-, 6α-hydroxy- and unsaturated bile acids by high-performance liquid chromatography-electrospray ionization-tandem mass spectrometry. Calibration curves for the bile acids were linear over the range of 10 to 2000 pmol/mL, and the detection limit was less than 2 pmol/mL for all bile acids using selected reaction monitoring analysis. The method was applied to measurements of adenosine triphosphate-dependent transport activities of the membrane vesicles for the above-mentioned hydroxylated and unsaturated bile acids. The present study demonstrated that the human multidrug resistance-associated protein 3 vesicles accepted 1β-, 6α-hydroxylated and unsaturated bile acids along with common bile acids, such as glycocholic acid and taurolithocholic acid 3-sulfate. The developed method is useful for measurements of bile acid transport activities.
A simple procedure is proposed to determine the total reflection X-ray fluorescence (TXRF) spectrometer sensitivity curve; this procedure provides better accuracy and exactitude than the standard established method. It uses individual pure substances instead of the use of vendor-certified values of reference calibration standards, which are expensive and lack any method to check their quality. This method avoids problems like uncertainties in the determination of the sensitivity curve according to different standards. It also avoids the need for validation studies between different techniques, in order to assure the quality of their TXRF results.
The bound state of water in PEG (polyethylene glycol)–H2O systems was studied by using HFS and DSC methods. Samples with the mixing ratios EO:H2O = 1:1 (a) and 1:10 (b), where EO indicates the ethylene oxide units in PEG chain, were heated from frozen state to melt state. Sample (a) gave an HFS peak corresponding to the weakly bound water, while sample (b) gave the peaks of both the bound and free water. DSC measurements gave quite similar patterns to those of HFS measurements, but with additional peaks corresponding to cold crystallization. The difference between the two measurements was reasonably interpreted by considering the origin of the cold crystallization.
A prussian blue (PB) electrodeposited on nano Ag-coated multiwalled carbon nanotubes (nano Ag-MWNTs) was reported. Also a PB/nano Ag-MWNTs composite modified glass carbon (GC) electrode was used to investigate the electrochemical behavior concerning the reduction of hydrogen peroxide. The experiment results showed that the PB/nano Ag-MWNTs/GC electrode had a wide linear range, a fast response time and high sensitivity toward the electrocatalytic reduction of hydrogen peroxide. PB and nano Ag-MWNTs had a synergistic electrocatalytic effect toward the reduction of hydrogen peroxide. The PB/nano Ag-MWNTs/GC electrode exhibited a wide linear response range of 8 × 10−8 to 5 × 10−3 mol/L with a correlation coefficient of 0.998 for the detection of hydrogen peroxide. Also the response time, detection limit (S/N = 3) and sensitivity of the PB/nano Ag-MWNTs/GC electrode were respectively determined to be 2 s, 4 × 10−8 mol/L and 920 A/mol cm2. Another attractive characteristic was that the PB/nano Ag-MWNTs/GC electrode showed high stability and reproducibility.
The reaction of free chlorine with tertiary ammonium or amine compounds in aqueous solution was studied by the amperometry at a rotating Pt-disk electrode. The amperometric method can be applied to follow the concentration of free chlorine (cCl) even in the presence of chloramine species. By addition of mono- and dibutylammonium to the solution containing free chlorine, the step-like decrease in cCl was observed, indicating the rapid formation of the stable chloramine species. By addition of tributylammonium, the cCl was decreased exponentially to nearly zero even if the free chlorine was present initially in excess. The cCl-t curves can be explained by tributylammonium-species-catalyzed decomposition of free chlorine to chloride ion. The catalytic decomposition was observed also with the tertiary-ammonium-based anion-exchange resins. Furthermore, the anion-exchange resins exhibited the decomposition of not only free chlorine but also chloramines in water.
Chemiluminescence from the vanadium and potassium permanganate reaction was studied under acidic conditions to develop a sensitive method for vanadium determination using the formaldehyde enhancement effect. The method was successfully applied to the determination of vanadium in seawater. Experimental parameters were optimized, including acid concentration, potassium permanganate and formaldehyde concentration. A linear calibration graph was obtained in the concentration range of 2.0 × 10−9 − 5 × 10−6 M with relative standard deviations (n = 4) in the range of 1.8 − 3.1%. The detection limit (3σ blank) was 8.0 × 10−10 mol L−1 with a sample throughput of 100 h−1. The effect of salinity and various interfering cations and anions were studied. The method was applied to determine total dissolved vanadium in seawater samples and certified reference materials after online reduction with amalgamated zinc column.
A weak cation exchange micro-column was incorporated into a sequential injection (SI) system to perform automatic hemoglobin (Hb) typing as an alternative way to measure HbE. Separation of HbF, HbA and HbA2/HbE was performed using phosphate buffer solutions in the pH range of 6 − 7 to create pH gradient mobile phase. The resultant chromatogram showed relative amounts of HbE to other types of hemoglobins in more quantitative detail than the conventional techniques such as dichlorophenol indophenol precipitation and micro-column anion exchange. The system is more economical than a commercially available ion-exchange HPLC analyzer for hemoglobin testing, though analysis time per run is longer due to the aspiration operation of the syringe pump of the SI system. It has been demonstrated that the system can differentiate negative (normal) from positive (HbE carriers) subjects.
A capillary-based pitch-variable array spotter, designed to dispense solutions in nanoliter volumes with high precision and density, was used to immobilize gene probes on a microelectrode array chip. Small volumes of the probe solutions were dispensed onto the microelectrodes, without any physical contact between the capillary ends and the electrode surfaces, to fabricate an electrochemical gene sensor array chip. The fabricated gene sensor array chip showed sequence-selective responses, expressed on a pseudocolor scale, to a target DNA sample. It was demonstrated that this dispensing technique provides integrated sensor array chips by dispensing small volumes of solutions of synthesized functional gene probes onto microelectrode array chips, a process not possible with conventional dispensing techniques.
Cultivation of rice plants (Koshihikari, IR4595 and IR28) in 250 mmol/L NaCl over 16 days provided interesting profiles of responses on a flow-through electrochemiluminescence (ECL) system with tris(2,2′-bipyridine)ruthenium complex. Although some time lags were noted among these rice plants, the increment in the ECL responses was clearly observed on the 11th day. The obtained ECL response profiles were consistent with the proline profiles obtained by HPLC. Such consistensy demonstrated that the present ECL system would find a utility as a useful sensor for salt stress on rice plants.
A flow system for electrochemical separation and detection of ions was constructed by connecting two oil/water (O/W)-type flow cells, in which a long polarizable O/W interface was formed at the inner surface of a porous poly(tetrafluoroethylene) (PTFE) tube. Using this system, acetylcholine and choline ions, whose ion-transfer potentials are different by only 60 mV, could be separated and determined simultaneously. It was thus shown that the present flow system is promising for the electrochemical flow separation/detection of ions and, in principle, also for electrochromatographic separation of ions.
A rapid method for the characterization of sake by measuring the ratio of the peak intensities of taste components in sake, using electrospray ionization/mass spectrometry (ESI/MS) has been developed. Twenty-six different kinds of sake samples were collected and analyzed by ESI/MS. The ESI/MS ion peaks were assigned to amino acids, organic acids, and sugars. Principal component analysis was performed using the respective peak intensities obtained by ESI/MS measurements. As a result, the cumulative proportion of the two first principal components was over 70%, and these components could be used for the characterization of sake.
The study presented in this paper concerns the extractability of rutin into an aqueous 1-butyl-3-methylimidazolium chloride (BMIM-Cl) solution. The effects of the concentrations of BMIM-Cl, amounts of Flos Sophorae Immaturus (FSI), extraction temperature and time on the rutin yield were examined. Under optimized extraction conditions, the rutin yield obtained by using aqueous BMIM-Cl corresponded to that obtained by using methanol. A newly established extraction method, followed by HPLC with ultraviolet detection, was applied to FSI samples with good recoveries and high repeatability.
In order to characterize the ion-exclusion and cation-exchange properties of an unmodified silica-gel column, the retention behaviors of Cr(VI) and Cr(III) ions were investigated using a Develosil 30-5 (150 × 4.6 mm i.d.) in the acidic region. Cr(VI) was separated from other anions by an ion-exclusion and ion-adsorption mechanism, and Cr(III) was separated from other cations with a cation-exchange mechanism. When using 2.0 mM oxalic acid (pH 2.6) as an eluent, a good separation of Cr(VI) and Cr(III) was obtained using conductimetric detection in 12 min. The method was successfully applied to the simultaneous determinations of Cr(VI) and Cr(III) added into tap-water and river-water samples.
A new and simple gas chromatography–mass spectrometry (GC-MS) method has been developed for simultaneous determination of estradiol valerate (EV) and medroxyprogesterone acetate (MPA) in a tablet formulation. The validation of the proposed method was carried out for selectivity, linearity, accuracy, precision, recovery, limits of detection and quantification. The developed method can be used for routine quality control (QC) analysis of titled drugs in combination in tablet formulation.
Airborne particulate matter (PM) collected in Bucharest (Romania) and Tokushima (Japan) was comprehensively characterized through multielemental analysis by ICP-MS to the PM samples. Prior to an elemental characterization of the sample, a multielemental determination method composed of acid digestion (HClO4/HNO3/HF or H2O2/HNO3/HF) and inductively coupled plasma mass spectrometry/inductively coupled plasma atomic emission spectrometry (ICP-MS/ICP-AES) was established to analyze a certified reference material of vehicle exhaust matter (NIES No. 8) for verifying the method. As the results, 39 elements in the certified reference material could be determined. They were a good agreement with the certified and reference values for HClO4/HNO3/HF acid digestion. Chalcophile elements, such as cadmium, antimony, and lead in Bucharest showed higher enrichment factors than those in Tokushima.
On page 84, the polarity of SP-ISS should be reversed in Fig. 6. The corrected figure is shown below. Accordingly, the polarity of the SP-ISS spin asymmetry on page 85 line 16 should also be reversed. These corrections modify our former interpretation that SP-ISS most sensitively detects the spin state of occupied levels close to the Fermi level, written on page 85. This should be changed to the expression that SP-ISS detects the total spin of electrons neutralizing He+ ions, where the electrons are not limited to the Fermi level. These corrections do not change the experimental result concerning the appearance of the spin-dependent scattered ion yield in Fig. 6. Therefore, the following two major conclusions of this paper do not change: the importance of the OP radiation polarization in PHe+, and the dependence of ion-scattering intensity on the surface spin polarization.