A fluorescent dye-labeled DNA probe was adsorbed and quenched on the monolayer of RuO₂ nanosheets. Significant fluorescent recovery was observed upon the addition of complementary DNA due to desorption of the probe from the surface of the RuO₂ nanosheet through duplex formation. The efficiency of fluorescence recovery was higher than that for graphene oxide, which was known as a quencher-free platform for the detection of nucleic acids in a homogeneous solution.

Highly sensitive and selective detection of various volatile organic compounds (VOCs) has been most needed in a wide range of fields, such as medical diagnosis, health supervision, industry-process control, and environmental monitoring. Since a semiconductor-type gas sensor is a typical promising candidate among various portable VOC-sensing devices, many efforts on developing these gas sensors are introduced in this article for the first time. Through some development stages, it has been well known that the temperature-modulated operation of gas sensors is one of effective ways to improve the magnitude of VOC responses. On the other hand, catalytic combustion-type gas sensors operated with a mode of pulse-driven heating were developed in the early 2000s, and they are named as “adsorption/combustion-type gas sensors” after their gas-sensing mechanism, based on the combustion of VOC adsorbates on the sensing material. The representative VOC-sensing properties of the adsorption/combustion-type gas sensors and recent material-design approach to achieve highly sensitive and selective VOC detection are summarized in this article.

A novel Au-Fe₃O₄ nanoparticles-based capillary column was fabricated by magnetic approach for open-tubular capillary electrochromatography (OT-CEC). The bifunctional dumbbell-like Janus Au-Fe₃O₄ nanoparticles (Au-Fe₃O₄ NPs) were prepared through a hydrothermal synthesis strategy, and the morphology was characterized by transmission electron microscopy (TEM). Multilayers Au-Fe₃O₄ NPs were easily coated onto the inner surface of silica capillary by an external magnetic field to generate an Au-Fe₃O₄ NPs-based column. Compared with a bare capillary, the modified surface exhibited more stable and suppressed electroosmotic mobility. The column showed good separation efficiency for neutral analytes in the OT-CEC separation mode, with theoretical plate numbers of up to 79705 per meter for naphthalene. The successful separation of dihydroxy benzene isomers and proteins demonstrated that the column exhibits a reasonable separation performance. The reproducibility of the Au-Fe₃O₄ NPs capillary was studied, with relative standard deviations (RSD) for day-to-day and column-to-column less than 1 and 1.75%, respectively.

An electrochemical vapor generation (EcHG) system to determine the cadmium content using atomic fluorescence spectrometry has been established. The EcHG system uses two serially-connected graphite tubes as two electrolysis cells and an AC to DC power wall plug adapter with the constant voltage mode as a power supply. The system did not have an ion exchange membrane and only needed a pump to transport the feed solution and waste. Under these optimized conditions, the detection limit (3σ) and the relative standard deviation were 0.05 ng mL⁻¹ and 3.2%, respectively. The EcHG efficiency was 38.4 ± 2.2%. The proposed technique has been successfully applied to determine the cadmium in three certified reference materials for environmental water and two drinking water samples.

Branched fatty chain fatty acids (BCFAs) are associated with the “mutton flavor” found with the aroma resulting from cooked older sheep meat with three BCFAs, 4-methyloctanoic (MOA), 4-ethyloctanoic (EOA) and 4-methylnonanoic (MNA) acids as the main compounds responsible for “mutton flavor”. Usually, BCFA analysis is done by gas chromatography (GC) with the use of quadrupole mass spectrometry (qMS) becoming predominant. 2-Butyloctanoic acid (2BO) has been used in this facility using as an internal standard to determine BCFA content in sheep fat. In this present work, GC-qMS, along with GC–quadrupole-time of flight MS (GC-QTOF-MS), have been deployed to characterize alkyl esters (as methyl, ethyl, propyl, and butyl) for MOA, EOA, MNA, and 2BO. This work presents, for the first time, the mass spectral characterization of 2BO for these alkyl esters using GC-qMS and GC-QTOF-MS.

Although an accurate detection of trace oil leaks is of the utmost important for soil protection, the typically used techniques fail to provide rapid assessment of less than 20 parts per million (ppm) of oil in soil. Terahertz (THz) time-domain spectroscopy, an optical method with high sensitivity to polar organics, was used to characterize the content of crude oil in soils. A linear model was built between the concentration of crude oil and the THz attenuation coefficient, which predicted the limit of detection ranging from 4.11 to 16.2 ppm. Some organics, such as aromatic and aliphatic compounds, contribute to larger absorption in the THz range than minerals. Effective-medium theory was optimized to elucidate the crude oil content dependence of THz dielectric constants. Consequently, THz technology could be an effective method for detecting trace oil leakage in soil.

A novel cationic iridium(III) complex phosphorescent probe (Ir-BE) containing aromatic boronate ester moiety as recognition unit was designed and synthesized. The probe exhibits ratiometric emission variations (I₄₉₀/I₅₅₀) with the color change from yellow to green only toward H₂O₂ with a broad pH range of 4 – 13. Different from other aromatic boronate-based probes, Ir-BE possesses larger Stokes shift (320 nm) and exhibits good linear correlation (R² = 0.998) between the emission ratio (I₄₉₀/I₅₅₀) and the H₂O₂ concentration in a range of 0 – 300 μM. The detection limit was as low as 0.21 μM. Furthermore, the real water sample studied further proved Ir-BE has excellent selectivity for the quantitative detection of H₂O₂.

A nanocarbon film consisting of nanocrystallites with mixed sp² and sp³ bonds formed by unbalanced magnetron sputtering, was studied with respect to changes in the characteristics caused by the surface oxygen concentration. An electrochemical pretreatment (ECP) was conducted to change the surface oxygen concentration of the nanocarbon film. X-ray photoelectron spectroscopy (XPS) measurements revealed that nanocarbon films with different amounts of surface oxygen could be prepared. In addition, we observed no significant increase of surface roughness (R_a) at the angstrom level after ECP, owing to a stable structure containing 40% of sp³ bonds. The electrode characteristics, including the potential window, and electrochemical properties for some redox species, such as Ru(NH₃)₆^3+/2+, Fe(CN)₆^3−/4− and some biomolecules, were investigated. The anodic potential limit became wider and ΔE_p of Fe(CN)₆^3−/4− became smaller at the treated nanocarbon film electrode than those of the as-deposited nanocarbon film electrode. Based on these results, we realized to measure uridylic acid (UMP) and inosine triphosphate (ITP) with a high oxidation potential by direct oxidation, which was difficult to measure at the as-deposited nanocarbon film electrode.

A micellar-enhanced photo-induced fluorescence (ME-PIF) method was developed to analyze, for the first time, oxadiazole herbicide (namely oxadiazon) in natural water samples. Photo-conversion under UV irradiation of the herbicide into strongly fluorescent photoproducts was performed in aqueous solution and in the presence of two surfactants, cetyltrimethylammonium chloride (CTAC) or Tween 20, at micellar concentrations. The ME-PIF parameters were optimized. The ME-PIF method gave very good results with satisfactory analytical performance for the determination of a selected pesticide with concentration linear dynamic ranges of over one to two orders of magnitude. It yielded good reproducibility (RSD values of between 3.6 and 9.6%) in tap, river and sea water spiked samples, and the limits of detection were in the ng mL⁻¹ range.

A simplified two-step mercury extraction procedure enabled the selective and reproducible mercury recovery from actual coal fly ash (CFA). The optimized extraction procedure involving conventional enzyme-linked immunosorbent assay (ELISA)-based immunoassay allowed the ultra-sensitive quantification of total mercury content in CFA. The total mercury content of 41 CFA samples were successfully determined using the above-mentioned method, and the results were in agreement with those obtained by standard instrumental analysis (thermal decomposition atomic absorption spectrometry) within a 15% coefficient of variation. Our method for total mercury quantification is not only simple but suitable for management of the mercury content at coal-fired electric power plants and landfill sites, which deal with large amounts of waste CFA.

We developed a novel metal adsorbent composed of bio-based materials, cellulose and a protein. The approach involved the immobilization of a hexa-histidine tag (His₆), which shows an affinity for an intermediate acid (metal ion) in Hard and Soft Acids and Bases (HSAB) theory, on cellulose by fusing with a carbohydrate-binding module (CBM). The results show that CBM-His₆-bound cellulose has adsorption selectivity reflecting the original properties of His₆. Additionally, we prepared three configurations of CBM-His₆ proteins, which were subsequently immobilized on filter paper for Ni²⁺ ion adsorption. Of these configurations, we found that the protein containing two His₆ tags at each terminus (N– and C–) of CBM exhibited the highest metal adsorption ability. Furthermore, XPS analysis confirmed the binding of Ni²⁺ ions on the cellulose.

This study describes a sample preparation method for trace element analysis using total reflection X-ray fluorescence analysis. The procedure of this method is as follows: 1) a hydrophobic-coated sample holder whose hydrophobic film at around the center of the surface is partially dissolved by acetone is prepared; 2) a droplet of a sample solution is dropped on the sample holder; and 3) the sample droplet is heated and dried while vibrating it. This sample preparation method is effective for reducing the size of the dry residue of the sample solution and suppressing the coffee-ring formation. Furthermore, this method leads to an enhancement in the intensity of an X-ray fluorescence line from an analyte element in the sample residue. In this study, this sample preparation method led to an improvement in the detection limit for vanadium in commercially available bottled drinking water.

The elemental and crystalline phase compositions of fly ash collected before and after spraying of the ash with slaked lime (first and second fly ash) and the bottom ash of municipal solid waste collected at an incineration plant were analyzed using powder briquette by X-ray fluorescence spectrometry and Rietveld refinement by X-ray diffraction. The crystalline and amorphous phase contents were quantified by adding 10% corundum as an internal standard. In the first fly ash, SiO₂, Cl, and CaO were the main components, and several thousand ppm (μg/g) of Zn and Pb were detected. Anhydrite, gehlenite, and amorphous phases were the main phases in the first fly ash samples. The components of the first fly ash originated exclusively from the incineration of municipal solid waste in a furnace. The crystal morphologies of the heavy elements in the ash samples were estimated by determining the correlations among the concentrations of all the elements. The heavy elements in the bottom ash showed no strong correlations with other elements; therefore, the heavy elements in the bottom ash were present in an amorphous phase.

The synergistic extraction of trivalent lanthanoid (Ln(III)) ions with 4-isopropyltropolone (Hipt) and 1,10-phenanthroline (phen) in o-dichrolobenzene (DCB) was investigated. The synergistic effect in DCB is more significant than that in toluene, and the polynuclear complexes found in toluene are not formed in DCB. Based on the 3-dimensional equilibrium analysis, the extracted species for La(III), Eu(III), and Lu(III) are found to be ion-pairs, such as Ln(ipt)₂phen·ClO₄ and Ln(ipt)₂(phen)·ClO₄ in the presence of NaClO₄ as a salt, and the extraction constants of the respective species were determined. The simultaneous extraction of different lanthanoids in the present extraction system was demonstrated. The separation factors between lighter lanthanoids were larger than those with 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester, an excellent extractant for the separation of lanthanoid ions, in decane.

A method for the simultaneous determination of 17 kinds of phthalate esters in capsanthin was developed by the QuEChERS (quick, easy, cheap, effective, ruggedand safe) pretreatment method coupled with gas chromatography–mass spectrometry(GC-MS). Capsanthin samples were extracted with acetonitrile, and then sodium chloride and anhydrous magnesium sulfate were added for salting out. After the extracting liquids were cleansed by florisil, the supernatants were analyzed by GC-MS. The limits of detection (LOD) and limits of quantitation (LOQ) ranged from 0.2 to 0.5 μg/g and 0.6 to 1.5 μg/g, respectively. DMP, DEP, DAP, DIBP, DBP, BMPP, DPP, DHXP and DCHP were in the range of 0.2 – 10 μg/g; DMEP, DEEP, BBP, DBEP, DEHP, DPhP, DNOP and DNP were in the range of 0.5 – 20 μg/g. And all had good linearity and the linear correlation coefficients (R²) were more than 0.995. The average recoveries of 17 kinds of PAEs of the three levels were between 82.8 and 118.1%, and the relative standard deviations (RSDs) were between 0.12 and 7.3%. It is a simple, rapid, accurate and reliable method for the rapid detection of PAEs in large quantities of natural plant extract samples.

A simple treatment method was proposed for the determination of iodine in eggs, followed by a flow-injection spectrophotometry based on the catalytic effect of iodine in the reduction reaction of Ce(IV) with As(III). The egg matrix was removed based on protein precipitation principles. Several protein precipitation methods were investigated. The treatment using trichloroacetic acid satisfactorily removed most of the egg matrix components. A colorless solution and a good signal were achieved. The method provided more reliable results compared to the conventional alkali dry ashing.

Quantitative analysis of red phosphorus in polypropylene was studied using a temperature programmable pyrolyzer in combination with a mass spectrometer. Evolved gas analysis (EGA) profiles were obtained by continuous measurements of evolved gases from a sample while heating the sample at a constant heating rate. During heating of the sample, red phosphorus sublimates into P₄ molecules, which have characteristic ions (m/z 31, 62, 93 and 124). Red phosphorus in polypropylene was determined from the m/z 62 ion peak area of the EGA profile with good reproducibility. The determined value was close to the value of original formulation and to the one determined by pyrolysis-GC/MS.