Rapid, accurate and sensitive ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) methods were developed and validated for the simultaneous quantitation of amoxicillin and clavulanic acid in human plasma and urine samples. Amoxicillin and clavulanic acid in both plasma and urine were extracted using a solid-phase extraction method. The compounds were separated on an Acquity UPLC HSS T3 column (2.1 × 100 mm, 1.8 μm). Ampicillin was used as the internal standard (IS) in plasma, while amoxicillin-d₄ and sulbactam were used as ISs in urine. The lower limit of quantitation was 0.0500 and 0.0250 μg/mL for amoxicillin and clavulanic acid in plasma, and 0.0500 μg/mL for both analytes in urine. The established methods were validated in terms of selectivity, precision, accuracy, linearity, matrix effect, recovery, carryover, interaction, dilution integrity and stability, and successfully applied to a pharmacokinetic study of amoxicillin sodium and clavulanate potassium (10:1) injection in healthy volunteers.

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Glycosylation plays an important part in many biological processes. However, many glycoproteins are either of low abundance or covered by other components in biological samples. Hence, developing new methods to measure the glycoproteins with both high efficiency and low detection limit is important. In this work, a self-assembled 4-mercaptophenylboronic acid film was coated on a quartz crystal microbalance chip. By optimizing the reaction time and the concentration of 4-mercaptophenylboronic acid, a sensor that specifically responded to glycoproteins was created. Then, several parameters for the prepared sensor were investigated and the working curve for representative glycoprotein–transferrin was established. The linearity range was from 50 to 400 ng/mL and the detection limit was 21.0 ng/mL. The sensor was used to detect transferrin in artificial urine samples. This sensor has a low detection limit of glycoproteins requiring only a small amount of samples, and thus has potential applications in both pharmaceutical and medical areas.

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To accelerate the vaporization, atomization, and ionization efficiencies in laser ablation inductively coupled plasma mass spectrometry, we merged HCl gas with laser-ablated particles before introduction into the plasma, to convert their surface constituents from oxides to lower-melting chlorides. When particles were merged with HCl gas generated from a HCl solution at 200°C, the measured concentrations of elements in the particles were 135% higher on average than the concentrations in particles merged with ultrapure water vapor. Particle corrosion and surface roughness were observed by scanning electron microscopy, and oxide conversion to chlorides was confirmed by X-ray photoelectron spectroscopy. Under the optimum conditions, the recoveries of measured elements improved by 23% on average, and the recoveries of elements with high-melting oxides (Sr, Zr, and Th) improved by as much as 36%. These results indicate that vaporization, atomization, and ionization in the ICP improved when HCl gas was merged with the ablated particles.

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A fluorescent probe 1 has been successfully developed to determine human serum albumin (HSA). Probe 1 expresses a dramatic fluorescence enhancement to HSA without interference from other amino acids. Under the optimal conditions, the calibration graphs are linear over the range of 0 – 13.3 μg/mL with the limit of determination of 0.61 μg/mL. Thus, this probe shows high sensitivity and selectivity to HSA.

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A newly designed oxime based probe, 2,4-dihydroxyacetophenone-oxime (DHAO), was found to recognize H₂AsO₄^– selectively with ∼3 fold "turn-on" fluorescence enhancement and LOD of 29 μM, K = (2.10 ± 0.54) × 10⁴ M^–1 in purely aqueous medium. The structures of the DHAO and its adduct with H₂AsO₄^– were optimized by DFT calculations. Intracellular imaging of As(V) in HepG2 cells demonstrate the possibilities of in vitro/in vivo applications for selective monitoring of such species.

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A method for direct and precise determination of Cd in seawater by ICP-QMS/QMS was developed, where a high matrix introducing unit permitted the direct introduction of seawater without clogging the cones while the matrix effect of seawater was canceled by standard addition. NH₃ gas was selected as the reaction gas for removing the MoO interferences with the measurement of Cd isotopes, effectively improving the signal to background ratio. The lower limit of detection obtained at ¹¹⁴Cd was 0.0002 ng mL^–1, which is enough for the determination of Cd in natural seawater. The validity of the present method was confirmed by the analysis of two certified reference materials, i.e. NASS-5 and NASS-6, whose observed values of Cd concentration agreed with the certified values. The analytical figures of merit of the present method were comparable to or better than those reported for direct analysis of seawater.

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Nanoparticles have been widely utilized to deliver drugs from blood vessels to target tissues. A crucial issue concerning nanoparticle-based drug delivery is to discuss the relationship between experimentally-obtained permeability and physical parameters. Although nanoparticles can permeate vascular pores, because the size and shape of the pores are essentially non-uniform, conventional animal testing and recent cell-based microfluidic devices are unable to precisely evaluate the effects of physical parameters (e.g. pore size and nanoparticle size) on permeation. In this study, we present a membrane-integrated microfluidic device to study permeation of nanoparticles through straight micropores. Porous membranes possessing uniform straight pores were utilized. The effects of pore size and pressure difference across the pores on nanoparticle permeation were examined. The experimentally determined permeability coefficient of 1.0 μm-pore membrane against 100 nm-diameter nanoparticles agreed well with the theoretical value obtained for convectional permeation. Our method can be utilized to clarify the relationship between the experimentally-obtained permeability and physical parameters, and will help rational design of nanomedicines.

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In this study, a novel fluorometric method for the determination of peroxynitrite anion (ONOO^–) scavenging (PAS) activity of amino acids and biothiols, which can mostly trap peroxynitrite in vivo, is described. This assay is based on the conversion of a gentisic acid probe to its non-fluorescent oxidation products with ONOO^–. The attenuation of the fluorescence intensity (FI) of the probe upon peroxynitrite attack is diminished with antioxidants, the difference in FI being related to the PAS activity of the antioxidants. The IC₅₀ (50% inhibitive concentration) values of biothiols, amino acids and tissue homogenates were estimated, in comparison with the reference Pyrogallol Red (PR) bleaching method. PR is the most suitable and frequently used dye to determine PAS activity, but is relatively insensitive. The developed fluorometric assay is highly sensitive to allow determinations of the PAS activity of amino acids.

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An online preconcentration system based on solid-phase extraction was developed for speciation and determinations of Cr in industrial water samples using flame atomic absorption spectrometry. A minicolumn packed with Amberlite XAD-16 loaded with salicylic acid was used to preconcentrate chromium species. All flow and chemical parameters that influence sorption were studied. The preconcentration factor and detection limit for the preconcentration time of 120 s were 79 and 0.10 μg L^–1, respectively. The concentration of Cr(VI) species was calculated by the difference of the total Cr and Cr(III). The relative standard deviation (RSD) (five replicate of measurements) for 50 and 100 μg L^–1 Cr(III) solution was 1.2 and 1.0% respectively. The accuracy of the method was verified by analyzing a standard reference material (NIST SRM 1640a, trace elements in natural water). The proposed preconcentration method was successfully applied to the determination of Cr species in industrial water samples with satisfactory results.

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The acid-base equilibrium of hexamethylenetetramine (hexamine) was analyzed with its effective electrophoretic mobility by capillary zone electrophoresis. Although hexamine is degradable in a weakly acidic aqueous solution, and the degraded products of ammonia and formaldehyde can be formed, the effective electrophoretic mobility of hexamine was measured in the pH range between 2.8 and 6.9. An acid-base dissociation equilibrium of the protonated hexamine was analyzed based on the mobility change, and an acid dissociation constant of pK_a = 4.93 ± 0.01 (mean ± standard error, ionic strength: 0.020 mol dm^–3) was determined. The monoprotic acid-base equilibrium of hexamine was confirmed through comparisons of its electrophoretic mobility with the N-ethylquinolinium ion and with the monocationic N-ethyl derivative of hexamine, as well as a slope analysis of the dissociation equilibrium.

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A rapid and sensitive high-performance liquid chromatography–mass spectrometry method was established to determine the trace residues of piperazine in vortioxetine hydrobromide. The presence of piperazine was determined by precolumn derivatization with dansyl chloride. Chromatographic separation was performed on a Waters SunFire C8 column (150 × 4.6 mm, 3.5 μm) in gradient elution mode, using formic acid and acetonitrile as mobile phase. Detection was performed in a single quadrupole mass spectrometer in single ion monitoring mode using positive ionization. An m/z value of 553 was selected for monitoring disubstituted piperazine by DNS-Cl. Linearity, accuracy, and precision were found to be acceptable over the piperazine concentration range of 0.3525 – 2.35 ng mL^–1. The limit of detection and limit of quantification of piperazine were 0.1175 and 0.3525 ng mL^–1, respectively, which complied with the requirements of qualitative and quantitative analyses. The method was deemed sensitive and efficient.

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Solid-state NMR observations of low-gamma half-integer quadrupolar nuclei, ³⁵Cl and ³⁷Cl, were demonstrated using a 24 T hybrid magnet (¹H resonance frequency of 1.02 GHz) comprised of the high-temperature (HTS) and low-temperature (LTS) superconductors, and compared with results using a 14.1 T standard NMR magnet. While at 24 T the linewidth is 1.7 times narrower than that at 14.1 T, the gain in the sensitivity is 7.0 times because of enhanced polarization, reduced linewidth, and the use of larger rotor. A simple theoretical model was used to rationalize the sensitivity enhancements. The ratio of ³⁵Cl and ³⁷Cl quadrupolar couplings agrees well with the ratio of quadrupolar moments, and no isotope-dependent chemical shift has been observed. In addition, the 3QMAS spectrum of ³⁵Cl is shown to demonstrate the high sensitivity rendered by the 24 T spectrometer.

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Bidentate organic molecules with imidazole or benzimidazole moieties connected to a rigid 1,3-diphenyladamantane spacer are simple and unique building blocks that facilitate the assembly of supramolecular architectures in the solid state via metal-coordination. Single-crystal X-ray analysis revealed that the complexation of bidentate ligand-bearing imidazole moieties with cobalt(II) or cadmium(II) ions in methanol/chloroform produced complexes that showed doubly-interpenetrated two-dimensional (2D) sheets through the formation of coordination bonds between the cobalt or cadmium metal centers and the nitrogen atoms of the imidazole groups. In the complexation of another ligand bearing a bulky benzimidazole group with cobalt(II) ion generated in methanol/chloroform, extended zigzag one-dimensional (1D) chains were formed, indicating that the molecular shape and bulkiness of the ligand design are crucial in the control of coordination polymers. The crystallization solutions were subjected to cold-spray ionization mass spectrometry (CSI-MS), and ion peaks derived from complexes with metal-ligand 1:2 and 1:1 were observed in complexation with ligands bearing the imidazole and benzimidazole moieties, respectively. The metal-ligand ratio in the CSI-MS analysis was identical to that found in the single-crystal X-ray analysis of an independent molecule. In addition, coordination oligomers with large molecular weight were detected as part of the obtained coordination polymers observed by CSI-MS/MS.

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The artificial bilayer single-channel recording technique is commonly used to observe detailed pharmacological properties of various ion channel proteins. It permits easy control of the solution and membrane lipid composition, and is also compatible with pharmacological screening devices. However, its use is limited due to low measurement efficiency. Here, we develop a novel artificial bilayer single-channel recording technique in which bilayers are made and channels are reconstituted into the membranes by contacting a gold electrode to the lipid-solution interface. Using this technique, we measured the single-channel currents of two channel-forming peptides, gramicidin and alamethicin, and a channel-forming protein, α-hemolysin. This technique requires only one action, allowing the technique to potentially be combined with high-throughput screening devices.

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We demonstrated a rapid immunoassay for detection of cat cystatin C (cCys-C) which is an important marker for chronic kidney disease in cats, using immuno-pillar chips. The required amount of reagent solution is 200 times smaller than that for the conventional ELISA in the 96-well microplate (0.5 μL versus 100 μL). In addition, the total assay time in the proposed method is more than 12 times shorter than in the conventional method (20 min versus 240 min). The limit of detection in the new method of 3 ng mL^–1 is comparable to that of the conventional method (1 ng mL^–1) and it is in the clinically relevant range.

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Single nucleotide polymorphisms (SNPs) in ADH1B and ALDH2, which encode alcohol dehydrogenase 1B and aldehyde dehydrogenase 2, respectively, are responsible for ethanol-metabolizing activity and alcohol-related disease. We developed a simple and rapid polymerase chain reaction-based restriction fragment length polymorphism (PCR-RFLP) method for the simultaneous genotyping of the genes in a single-tube reaction. Using an alkaline lysate of a human hair root as a template, SNP-containing regions of each gene were PCR-amplified simultaneously. The PCR products were directly applied to double restriction digestion, followed by agarose gel band analysis. The duplex PCR-RFLP allows for the simultaneous and accurate determination of the SNP genotypes of ADH1B and ALDH2 within 1.2 h.

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The co-use of two neutral ligands, tri-n-octylphosphine oxide (TOPO) and dicyclohexano-18-crown-6 (DC18C6), for ion-pair extraction of divalent strontium (Sr²⁺) with bis(trifluoromethanesulfonyl)imide anion (Tf₂N^–) showed unique synergistic effect. The extracted species in use of a single ligand is Sr(TOPO)₃²⁺·2Tf₂N^– or Sr(DC18C6)²⁺·2Tf₂N^–, whereas the co-use resulted in extraction enhancement based on additional formation of Sr(DC18C6)(TOPO)²⁺·2Tf₂N^– and Sr(DC18C6)(TOPO)₂²⁺·2Tf₂N^–.

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Ionic liquid aqueous two-phase systems were delivered into a capillary tube to achieve tube radial distribution flow (TRDF) or annular flow in a microspace. The phase diagram, viscosity of the phases, and TRDF image of the 1-butyl-3-methylimidazolium chloride and NaOH system were examined. The TRDF was formed with inner ionic liquid-rich and outer ionic liquid-poor phases in the capillary tube. The phase configuration was explained using the viscous dissipation principle. We also examined the distribution of rhodamine B in a three-branched microchannel on a microchip with ionic liquid aqueous two-phase systems for the first time.

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We have developed a rapid genetic testing system integrating nucleic acid extraction, purification, amplification, and detection in a single cartridge. The system performs real-time polymerase chain reaction (PCR) after nucleic acid purification in a fully automated manner. RNase P, a housekeeping gene, was purified from human nasal epithelial cells using silica-coated magnetic beads and subjected to real-time PCR using a novel droplet-real-time-PCR machine. The process was completed within 13 min. This system will be widely applicable for research and diagnostic uses.

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Electrolytic cells for electrochemical oxygen demand (ECOD) measurements based on total electrolytic decomposition at a boron-doped diamond (BDD) electrode were developed for rapid measurement of organic pollutants at low concentrations. Using improved electrolytic cells designed for efficient mass transfer, the ECOD for 10 μM potassium hydrogen phthalate (theoretical ECOD: 2.3 mg-O₂ L^–1) was determined in a relatively short electrolysis time. Thus, ECOD measurements using these cells would be useful for estimating organic water pollution in industrial waste and lake water.

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