In this work, an alkaline phosphatase (ALP) biosensor was established based on G-quadruplex/N-methylmesoporphyrin IX (G4/NMM) and p-nitrophenol (PNP). Because the absorption of PNP was close to the excitation wavelength of G4/NMM, PNP could reduce the fluorescence of G4/NMM. Meanwhile, PNP was the hydrolysis product of p-nitrophenylphosphate (PNPP) by ALP. Therefore, ALP could be detected. This ALP biosensor had a linear analytical range from 2.5 to 25 U/L a the detection limit of 0.81 U/L. Moreover, it showed a satisfactory selectivity and recovery rates.

Matrix-assisted laser desorption/ionization-based mass spectrometry imaging (MSI) of separated lipids on thin-layer chromatography (TLC) plates or followed by blotted hydrophilic polyvinylidene fluoride (PVDF) membranes has become a powerful tool in lipidomic analyses. However, background peaks in MS spectra often cover lipid peaks in a low amount/ionization effect; consequently, only low intensities/resolutions MSI are obtained. To address the aforementioned problem, we attempted 1,2-dichloroethane pre-washing of TLC plates before development and found that backgrounds could successfully be removed from the TLC plate or PVDF membrane.

User-friendly fingerprint powders, namely efficient, low-cost and nontoxic ones, are always desirable for the development of latent fingerprints (LFPs). Here, we described the use of pristine graphic carbon nitride quantum dots (g-C₃N₄ QDs) as a new kind of user-friendly fingerprint powder. The g-C₃N₄ QDs can be easily prepared from urea and sodium citrate precursors through low temperature solid-phase reaction. Due to their good optical properties and selective interactions with secretion residuals, the g-C₃N₄ QDs powders were exploited to develop LFPs on different substrates by the powder dusting technique. The LFP images on a plastic bag exhibited a high ridge and furrow contrast ratio, allowing for easy identification of level 1 – 3 details of LFPs. This work indicates that the g-C₃N₄ QD powders provide good performance for LFP visualization and is likely to be adopted for some applications in forensic investigations.

X-ray reflectivity measurements were performed for the leucine and lysine-based LKα14 peptide designed to adopt an α-helical conformation at the air–water interface. The electron density profiles along the surface normal were calculated from the atomic coordinates predicted by an electronic structure program to fit the X-ray reflectivity curve. At the concentration of the monolayer formation, the long axis of the α-helix adsorbed parallel to the water surface, and the central part was revealed to be submerged in water. On the other hand, at 100 times higher than the surface area density of the monolayer formation, the double layer is formed in which the long axis of the α-helix is parallel to the water surface and only the peptide in the second layer is submerged in water.

We present a lithography-free procedure for fabricating intrinsically three-dimensional microchannels within PDMS elastomers using nylon monofilament molds. We embedded nylon monofilaments in an uncured PDMS composite to fabricate straight channels of desired length, for use as molds to form the microchannels. Next, we fabricated two layer devices consisting of dialysis membranes, which preconcentrate specific proteins in accordance with molecular weight, in between two layers of PDMS substrates with embedded microchannels. Because of the membrane isolation, analyte exchange between two fluidic layers can be precisely controlled by an applied voltage. More importantly, given that only small molecules pass through the dialysis membrane, the integrated membrane is suitable for molecular sieving or size exclusion for a concentrator prior to microchip electrophoresis. Researchers can use our microchip design for online purification and preconcentration of proteins in the presence of excess reagent immediately after fluorescent labeling. This method’s technical advantage is that three-dimensional microstructures, such as microchannels that have a circular cross-section, are readily attainable and can be fabricated in a straightforward manner without using specialized equipment. Our method is a low-cost, environmentally sustainable procedure for fabricating microfluidic devices, and will render microfluidic processes more accessible and easy to implement.

We present an analytical method for dissolved oxygen based on the quantification of Mn(III) absorbance in a water sample. After Mn(II) reacts with the oxygen molecules in water, Mn(III) is formed and stabilized by hexa-metaphosphate under acidic conditions. The UV visible absorbance of Mn(III) is proportional to the oxygen concentration in the water sample. Compared to the Winkler method, the proposed method has the same accuracy (R = 0.9992 at 0 – 52 mg dm⁻³) but requires fewer reagents; furthermore, it does not involve titration. Interferences from nitrite and iodate were not observed. This procedure can be used to accurately and quickly determine the oxygen concentrations in different natural water sources, including seawater.

A signal-on supersandwich type of electrochemiluminescence (ECL) DNA biosensor was developed based on the poly(aniline-luminol) nanowires (PALNWs) modified electrode and enhancement of ferrocene (Fc) on ECL of luminol. Aminated capture DNA was covalently linked to the PALNWs on the electrode surface by the crosslinking of glutaraldehyde. In presence of target DNA, its 3′ terminus hybridizes with the capture probe and the 5′ terminus hybridizes with ferrocene labeled DNA (Fc-DNA) to form a long DNA concatamer supersandwich structure. The ECL intensity of the prepared biosensor was clearly improved by increasing the concentration of target DNA due to the enhancement of ferrocene on luminol ECL. The difference of the ECL intensity in the absence and presence of target DNA was used to monitor the hybridization event. The difference of ECL linearly increased with the logarithm of target DNA concentration in the range from 1.0  ×  10⁻¹⁶ – 1.0  ×  10⁻⁸ mol L⁻¹ with a detection limit of 5.8  ×  10⁻¹⁷ mol L⁻¹. The sensor had high sensitivity and wide linear relationship for the detection of target DNA.

The Raman shift is one of the most important parameters in Raman spectroscopy, and is calculated from the difference in the wavenumbers for excitation and for Raman scattering. Because the observed shifts are strongly dependent on the spectrometer and the measurement conditions, physically and chemically stable reference materials for Raman-shift validation are required. We reliably estimated the Raman shift and evaluated its uncertainty for peaks of a 4-mm-thick, 25-mm-diameter polystyrene disc by using a HeNe laser and Raman-scattered light calibrated with Ne/Ar emission lines. We considered uncertainties originating from the fitting, repeatability, and reproducibility of both the Ne/Ar emission lines and the Rayleigh/Raman-scattered lights, as well as the wavenumber of the unstabilised HeNe laser, and pixel and spectral resolutions. We also considered uncertainty originating from inhomogeneity among and within discs, as well as their long-term stability. The obtained Raman shifts of 11 peaks (reference values) were comparable to those described in ASTM E1840 with expanded uncertainty at 1.1 or 1.2 cm⁻¹ (k = 2, coverage factor).

Abnormal levels of biothiols, such as cysteine (Cys), homocystine (Hcy), and glutathione (GSH), are generally known to result in various diseases. A fast dual-responsive OFF-ON fluorescent probe HBO-AC was synthesized and developed. Non-fluorescent HBO-AC can sense Cys by regaining fluorescence at 444 nm within 10 min and a response to GSH by restoring fluorescence at 349 nm within 20 min. There is no mutual interference with Δλ ca. 100 nm. A novel method was developed by utilizing a low reaction rate between HBO-AC and Hcy to eliminate common interference from Hcy. A successful determination of Cys and GSH in fetal bovine serum (FBS) indicated that the probe had potential application for clinical diagnosis. Moreover, it was confirmed that HBO-AC can resist interference from protein to some extent, since FBS was not pretreated before use.

A magnetic starch modified with 3,5-diaminobenzoic acid and 3-aminopropyltriethoxysilane (Fe-starch@DABA-APTES) was synthesized and applied as adsorbent for the extraction of organochlorine pesticides (OCPs). Magnetic solid-phase extraction was developed using 75 mg of the sorbent and 15 mL of a sample solution. Extraction was conducted on a vortex mixer for 40 s. The adsorbent was collected using an external magnet before eluting the analytes using 0.5 mL of methanol. Quantification of the analytes was performed using gas chromatography with a micro-electron capture detector. The linearity was obtained for the studied OCPs in the range between 0.01 – 2.00 μg L⁻¹. The detection and quantification limits were obtained in ranges of 0.5 – 4.0 and 1.5 – 15.0 ng L⁻¹, respectively, with enrichment factors of up to 39. The precision in terms of the intra- and inter-day relative standard deviations (RSDs) were below 4.75, and 9.25%, respectively. The developed method has been applied in natural water and agricultural product samples. The recoveries ranged between 59.83 – 132.67% (RSDs < 10.73%).

The moment analysis method for chromatographic behavior in core-shell columns was simplified. Mass-transfer phenomena other than intra-stationary phase diffusion are analyzed while considering that the packing materials are spherical particles. The manner of intra-stationary phase diffusion is analyzed while assuming a hypothetical flat plate. For most core-shell particles commercially available, the geometry of a spherical thin layer can be supposed as a hypothetical flat plate with a relative error of less than ca. 2% because the thickness of the shell layer is sufficiently smaller than the diameter of whole particle. This supposition makes moment analysis easier because the moment equations for flat plates are simpler than those strictly developed for core-shell particles. Some chromatographic data measured using a core-shell column were analyzed by the simple moment analysis method to confirm its usefulness. It was demonstrated that the method is effective for a preliminary study of mass-transfer kinetics in core-shell columns.

In the analysis of short-chain carboxylic acids such as formic acid and acetic acid in aqueous solution using extractive alkylation gas chromatography, tetrahexylammonium bromide (THAB) as a phase-transfer catalyst (PTC) causes a high intensity and broad peaks in the gas chromatogram, and interfere with the detection of carboxylic acid derivatives. By an easy treatment of the extractive alkylation solution with perchloric acid and n-hexane, it is possible to remove more than 95% of THAB, and to provide good gas chromatogram with a little admixture of carboxylic acid derivatives. The desensitization was 16% at the maximum, the contamination of the glass insert in gas chromatograph and liquid phase in column by THAB was minimized, and trouble in continuous measurement could be avoided.

The chemical states of heavy metals and radioactive Cs were estimated in fly ash sampled at Fukushima prefecture, Japan. Estimating the speciation of incinerator fly ash is important to ensure an appropriate and efficient management of fly ash generated from disaster-related waste. In this study, fly ash collected at a waste incineration facility in Fukushima prefecture was treated using a sequential extraction test. The test results indicated that the solubility behavior of radioactive Cs was similar to that of NaCl and KCl, and approximately 60% of radioactive Cs was included as water-soluble chloride compounds in the fly ash sample. Most heavy metals eluted in three fractions, in the extraction steps for carbonate-bound, free oxide, and bound to organic matter species. The chemical states of elements in the three non-water-soluble fractions and residue showed minimal elution into the environment. Therefore, most heavy metals in the fly ash exhibited minimal elution into the environment.

A cell-killing ability of natural killer (NK) cells has been evaluated by the leakage of marker molecules from target cells. Lactate dehydrogenase (LDH) and calcein are two major non-radioisotope markers used for the killing assay. The spontaneous death of NK cells during the killing-assay of cells is a major issue in the assay because it provides background signals to increase errors. In this study, the effect of the spontaneous death of NK cells on the killing assays based on LDH and the calcein method was comparatively evaluated. We found that the calcein method is much less sensitive to the spontaneous death of NK cells to enable an accurate evaluation of the cell killing.

Synthetic cathinones are a type of new psychoactive substances (NPS) that have been seriously abused. Owing to the rapid variation in their structures, the absence of reference standards poses a challenge in quantitative investigations. In this study, a ¹H quantitative nuclear magnetic resonance (¹H qNMR) method was established using maleic acid as the internal standard and the shared signal (i.e., the methylidyne hydrogen) on the parent synthetic cathinones structure as the quantitative peak. Taking 3-methoxy-2-(methylamino)-1-(4-methylphenyl)propan-1-one (mexedrone) as an example, this study optimized the acquisition parameters and conducted method validation, including an evaluation of the specificity, linearity, accuracy, precision, and robustness. Using this ¹H qNMR method, the contents of mexedrone and its analogues, including 1-(3-chlorophenyl)-2-(ethylamino)-propan-1-one (3-CEC), 4-chloro-α-pyrroli-dinopropiophenone (4-Cl-α-PVP), 1-(3,4-methylenedioxy-phenyl)-2-propylamino-propan-1-one (propylone), and methcathinone, were obtained. The obtained results showed that the method was accurate, rapid, versatile, and can be used to address the qualitative and quantitative issues related to similar substances.

The development of simple and sensitive detection methods for tetracyclines (TCs) is crucial for their routine detection. The present study developed a colorimetric method for the detection of TCs based on the in-situ generation of AuNPs, which were subsequently coupled with a gold staining reaction. Briefly, TCs containing phenolic groups reduce HAuCl₄ to form gold nanoparticles (AuNPs) as gold seeds. In the gold staining process, the gold seeds catalyze the reduction of HAuCl₄ by NH₂OH to form gold atoms that deposit on the surface of AuNPs, resulting in the enlargement of AuNPs. Sensitive detection of TCs was achieved by employing the gold staining technique. As low as 14, 18.9, and 1.98 nM of oxytetracycline (OTC), tetracycline (TC), and doxycycline (DC), respectively, could be sensitively detected. The proposed method also exhibited good repeatability and specificity, and then was applied to the determination of OTC in milk samples.

A conductive molten salt was synthesized by using natural pyrite (PR) and silver nanoparticles (Ag) at 450°C using a molten salt method. The molten-salt-composite (PR/Ag) was used as an electrocatalyst to detect hydrogen peroxide (H₂O₂). The as-prepared PR/Ag possessed higher conductivity than natural PR. It exhibited a high sensitivity of 603.54 μA mM⁻¹ cm⁻² for the detection of H₂O₂, with a linear range of 0.1 to 30 mM, and a detection limit of 0.02 mM (S/N = 3). In addition, the PR/Ag sensor exhibited good selectivity to H₂O₂, resisting interference from other potential interferent compounds (e.g. uric acid, glucose, fructose and common metal ions (K⁺, Mg²⁺, Na⁺)). The approach is considered to provide a sensitive, selective, and reliable tool for highly detection of H₂O₂.

Enterohemorrhagic Escherichia coli are a dangerous bacterium known to be harmful to the human body, with some infections even resulting in death. Given this danger, food factories are required to perform a quick bacterial test to confirm the absence of this pathogen prior to shipping. We have developed a novel molecular imprinting polymer (MIP) particle that has encapsulated gold nanoparticles (AuNPs) and which can function as both a receptor and an optical signal transmitter in biological systems. This MIP particle is artificially synthesized and can be engineered to specifically recognize and capture antigens on the bacterial cell membrane. In addition, MIP particles containing AuNPs generate strong scattered light signals, and binding of the MIP particles improves the optical intensity of the target bacterial cells. This enables clear visualization under a dark-field microscope and quantification of the target bacteria using the scattering light intensity. Here we describe the successful quantification of Escherichia coli O157 cells in real meat samples using this technology in conjunction with a simple labelling step.

We investigated the chemical behavior of lanthanides (Ln) by multistage extraction. Using 10 aqueous phases with Ln and 3 organic phases, we drew the breakthrough curves for light and middle Ln. Our study reveals that the limit of metal extraction depends on their D values and the metal concentration employed in experiments. From the multistage extractions of 15 stage aqueous phases and 15 stage organic phases, three curves (extraction curves, back-extraction curves, and separation curves) were obtained. Setting appropriate conditions, adequate separation of light Ln from middle ones can be achieved. As an example, under the condition of the separation curve experiment (aqueous phase: 0.5 M HNO₃, organic phase: 0.1 M TDDGA (N,N,N′,N′-tetradecyl-diglycolamide) in n-dodecane), the recovery of more than 99% of Sm in the organic phase with less than 1% of Nd can be obtained, even in the case of two metals adjacent to each other in the Ln series.

In microfluidics, various chemical processes can be integrated utilizing parallel multiphase flows. Our group has extended this research to nanofluidics, and recently performed the extraction of lipids using parallel two-phase flow in nanochannels. Although this was achieved in surface-modified nanochannels, a stable condition of parallel two-phase flow remains unknown due to difficulties in device fabrication, for a suitable method of bonding surface-modified substrates is lacking. Therefore, research on parallel two-phase flow in nanochannels has been limited. Herein, a new bonding method which improves the wash process for the substrates and increases the bonding rate to ∼100% is described. The conditions to achieve parallel organic/aqueous two-phase flow were then studied. It was revealed that in nanochannels, higher capillary numbers for the organic phase flow were required compared to that in microchannels. The newly developed fabrication process and flow regimes will contribute to realize integrated nanofluidic devices capable of analyzing single molecules/cells.

The relationship between the width and height of the π* peak on X-ray absorption near edge structure (XANES) in the C K region of graphitic carbons is investigated from XANES measurements and theoretical analysis. This relationship is herein named the “characteristic diagram of π* peak profile”. Mechanically ground (MG) graphite experimentally exhibits a linear correlation on the diagram. To understand the linear correlation, C K-XANES of the graphitic hexagonal carbon layers are calculated using first-principles calculations by focusing on the edge carbon atoms. The linear correlation is well explained by the ratio of the edge carbon atoms of the graphitic hexagonal carbon layers. The characteristic diagram of π* peak profile is applied to industrial carbon black (CB) for identification. CBs exhibit identical distributions on the diagram, which depend on their uses. It is therefore confirmed that the proposed characteristic diagram of π* peak profile can be a useful tool to identify graphitic carbons from the edge carbon atoms.

Superheated water extraction (SWE) of pesticide residues in a cabbage sample was demonstrated. The recovery yields of several relatively polar pesticides (log P_ow < 3) by the spike-and-recovery method at 100°C were acceptable. Increasing the extraction temperature up to 150°C led to enhanced extraction efficiency except for pesticides that induced degradation. The recovery yields of some target pesticides having log P_ow values of 3.5 – 4 were effectively enhanced by increasing the number of extraction cycles. The observed concentration of fenitrothion in a cabbage sample was comparable with those by the official Japanese analytical method. These results suggested SWE is potentially suitable for the extraction of different relatively high-to-medium polarity pesticides.

Chemical derivatizations have been extensively developed for highly sensitive detection of bioactive small peptides; however, their advantages from the viewpoint of longer oligopeptides remain unverified. In this study, electrospray-ionization (ESI)–mass spectrometric (MS) detection of synthetic di- to pentapeptides consisting of glycine and sarcosine were characterized by four amine derivatization methods. It was concluded that the ESI-MS detection of di- to pentapeptides was characterized by the molecular surface area of derivatized peptide moieties with an optimal value of 250 – 300 Ų, regardless of hydrophobicity and derivatization methods.

With the increasingly wide industrial use of rare earth elements (REEs), their release into marine systems makes it important to understand in what quantities they occur and to what geochemical processes they contribute, preferably using direct analytical methodology. In this study, analytical performance of high-resolution ICP-MS was assessed with regard to quantification of REEs in seawater without matrix separation and analyte preconcentration. With optimized sample dilution, precise and interference-free quantifications of most of the REEs in samples taken from Kara Sea were obtained, with an accuracy of 3 to 9% (against the independently asserted values), repeatability of 3 to 5%, and intermediate precision and reproducibility, averaging 4 and 11%, respectively. The method was further validated by using a certified reference material for nearshore seawater. However, the limits of detection obtained (0.04 – 0.38 ng L⁻¹), while not significantly inferior to those obtained after sample enrichment, appear to be not low enough to analyze high salinity sea samples (over 30 parts per thousand) or open-ocean water samples, which require higher dilution factors or contain (much) lower REE concentrations, respectively. Therefore, it was concluded that the direct determination of REEs is only possible from samples with moderate salinity such as estuarine or shallow-sea water. In the latter case, the longitudinal REE profiling assayed by ICP-MS allowed us to assume that the export of the contaminated material from land areas into estuaries and then to the sea by rivers may substantially contribute to the seawater pool of REEs.

For size analysis of small nanoparticles (i.e., nanoparticles smaller than 10 nm) using spICP-MS, two approaches were employed to improve the signal-to-noise ratio of ion signals emanating from small nanoparticles. The first one was enhancement of the instrumental sensitivity using a desolvating system. The second approach was separation of the ion signals from background signals through a deconvolution method. A combination of these approaches enabled us to measure 5 nm gold nanoparticles, and the calculated size detection limit was 3.8 nm.

The adsorption properties of Pu(IV), Am(III), Cm(III), and U(VI) on desferrioxamine B-immobilized micropolymeric resin (DMPs) and adsorbed species were elucidated using thermodynamic constants and log β values. This allowed the determination of adsorption characteristics (91, 95, 88, and 97% for Pu(IV), Am(III), Cm(III), and U(VI), respectively) and individual pH-independent adsorption properties. Pu(IV) could be separated from Am(III), Cm(III), and U(VI) at pH 2. The separation of Pu(IV) from Am(III), Cm(III), and U(VI) was achieved by controlling the pH of the solution using a single resin.

A scanning probe microscope (SPM) operating in air and liquid was constructed using an open-source control software running on Linux, a correspondingly developed commercial SPM controller and a commercial STM head. The results are shown for highly oriented pyrolytic graphite (HOPG) and Au(111) substrate surfaces, which are typical samples for SPM measurements. The cost of building the system was much lower than that of commercial products with comparable performance. The system has great scalability, and can be applied to a various environment, such as ultra-high vacuum systems.