In this study, a new molecularly imprinted polymer (MIP) based nanocomposite was synthesized then used to determine epinephrine (EPN) by the use of an electrochemical sensor modified by it. Typical techniques for the synthesis of MIP have disadvantages, such as weak binding sites, low mass transfer and low selectivity. One of the ways to improve electrochemical properties is the use of graphene oxide (GR-Ox) and modification of its surface. For this purpose, GR-Ox was initially magnetized (MGR-Ox), then its surface was coated with a silica layer, and gold nanoparticles (AuNPs) were coated on its surface. Subsequently, copolymerization of methacrylic acid (MAA) and N,N′-methylene-bis-acrylamide (MBA) in the presence of EPN was performed on the MGO-AuNPs surface. Afterwards, a selective carbon paste electrode (CPE) with synthetic nanocomposite was fabricated to detect EPN. Under optimal conditions, a linear range from 10⁻⁸ to 5.0 × 10⁻⁷ M was obtained for the measurement of EPN in urine and blood with a detection limit of 5 × 10⁻⁹ M (S/N = 3).

A microwave-assisted diazotization reaction of ciprofloxacin was used for the analysis of ciprofloxacin in pharmaceutical samples. The ciprofloxacin was diazotized with phenol using acidified sodium nitrite in a domestic microwave oven. Faster microwave heating and microwave effects were found to be very effective for the process of diazotization. The microwave-assisted reaction was initiated in an acidic media and the colored product was stabilized in a slightly basic medium using a NaOH solution as a neutralizer. The product was found to exhibit the maximum absorbance at 440 nm. All of the experimental conditions like the concentration of reagents, microwave power and reaction time were optimized. The optimum concentrations for phenol, sodium nitrite, HCl and NaOH were found to be 140 ppm, 300 ppm, 0.006 M and 0.006 M respectively. The optimum reaction time was found to be 2 min and a medium high power of the microwave was found to be most effective. The limit of detection (LOD) and the limit of quantification (LOQ) were found to be 1.08 and 3.61 mg L⁻¹ respectively. The developed method was successfully applied for the determination of ciprofloxacin in pharmaceutical samples. This new spectrophotometric method for the analysis of ciprofloxacin is fast, sensitive, easy and cost effective.

A novel fluorescent turn-off sensor JM for hypochlorite was synthesized. JM showed a remarkable selectivity for ClO⁻ over diverse competitive analytes, including reactive oxygen species (ROS), via deprotonation reaction. Detection limit for ClO⁻ turned out to be 0.60 μM. Sensor JM successfully determined ClO⁻ in natural water samples with satisfactory recovery. The sensing mechanism of JM to hypochlorite was demonstrated by fluorescent and UV-visible spectroscopy, ESI-mass, NMR titration and TD-DFT calculations.

A new preconcentration method using solid phase extraction (SPE) was developed by immobilizing dithizone (DZ) and 1,4-diphenylsemicarbazide (DPC) on oxidative activated carbon and then using this for the speciation and preconcentration of mercury species (Hg(II) and MeHg(I)) by flow injection cold vapor atomic absorption spectrometry (FI-CVAAS). The SPE experimental conditions were investigated including pH, amount of adsorbent and flow rate. The elution parameters and effect of foreign ions were also elucidated. Under the optimized conditions, the calibration graph was linear in the ranges of 0.015 – 3.0 μg L⁻¹ of Hg(II), with a detection limit (LOD) of 0.0155 μg L⁻¹, corresponding to three times the standard deviation (3SD, n = 20). The precision of the method, defined as percentage relative standard deviation (%RSD) for mercury was 1.25 – 3.79% at concentrations of 0.1 – 1.0 μg L⁻¹, for which a preconcentration factor of 20 was obtained for Hg(II). The proposed method was validated by determining the mercury concentration in standard reference materials, and successfully applied to the speciation of mercury in several water and freshwater fish samples.

A near-infrared laser-induced surface deformation (NIR-LISD) microscope is developed and is applied to the dynamic viscoelastic measurements of the surface of a living plant cell. In the microscope, the deformation of the surface is induced by an NIR laser beam, and then the change in intensity of the probe beam reflected from the surface reflects its viscoelasticity. The application of the NIR laser beam has a great advantage for the prevention of damage to the plant cell compared to the irradiation of a visible laser beam in LISD measurements. The NIR-LISD microscope allows for discriminating the differences in power spectra between the subapical and lateral regions of single rhizoids. It is a useful method for the dynamic viscoelastic measurements of cells, such as plant cells, that are damaged due to the strong absorption of ultraviolet or visible light.

Surface-enhanced Raman spectroscopy (SERS) has gradually proved to be a powerful tool with wide applications in various fields. Here, a simple and rapid SERS method was developed for the determination of ketamine in urine based on silver aggregates as a SERS substrate. Ketamine in urine were demonstrated by the SERS technique with silver sol aggregated by a 0.5 M NaBr solution. The limit of detection for ketamine in urine could be obtained as low as 7.5 ppm, and a linear relationship for ketamine in urine between the Raman intensity and the concentrations was achieved in the range from 7.5 to 150 ppm (R² = 0.977). Additionally, the recovery of this method ranged from 95.7 to 104.9%, which laid a favorable foundation for the rapid and reliable quantitative detection of ketamine in urine. Therefore, this SERS approach with high sensitivity and simplicity has a great prospect for the real-world application of ketamine in urine.

This paper describes a simple method for quantifying phthalates via the conversion of anhydrous phthalates to a dye. The phthalate was hydrolyzed with sodium hydroxide and dehydrated to form phthalic anhydride, which was converted to a marker, namely fluorescein, by reaction with resorcinol. Concentrated sulfuric acid was used as the catalyst. The presence of a phthalate was determined by absorbance spectrophotometry. The detection limit of this method for di(2-ethylhexyl) phthalate was 0.1 μmol, and the relative standard deviation with respect to reproducibility was approximately 10% (n = 3). For other phthalates, namely diisobutyl phthalate, dibutyl phthalate, bis(butylbenzyl) phthalate, di-n-octyl phthalate, diisononyl phthalate, and diisodecyl phthalate, the absorbance deviation was less than 20%, which is within the acceptable range for screening purposes. Because the phthalates were hydrolyzed to enable colorimetric determination, the identification of individual phthalates is beyond the scope of this method. However, this simple colorimetric method can easily be used to determine the total amount of phthalates in real samples at the sub-micromolar level, by converting the phthalates to dyes. The applicability of this method was investigated by analyzing actual samples containing various phthalates. The quantitative results were almost the same as those obtained by using a conventional gas chromatographic method.

In this study, we developed an electrochemical sensor for ochratoxin A (OTA) by using an aptamer having a dithiol-based anchor, which exhibited higher stability on a gold electrode than a monothiol-based aptamer because of its two anchors. The sensor was also based on a signal-on scheme that produces a signal current resulting from structure-switching of the aptamer upon interaction with OTA. For simple fabrication of this sensor, the non-covalent interaction of methylene blue with the aptamer was also employed as an electrochemical indicator. In this study, the performance of the sensor, including the dissociation constant of the aptamer–OTA complex, was characterized. The proposed sensor exhibited high reproducibility and enough sensitivity to detect the minimum amount of OTA required for the analysis of real food samples with a limit of detection of 113 pM.

We present a microRNA (miRNA) detection method that achieves enhanced sensitivity by means of a power-free microfluidic chip without the requirement of an external power source. The miRNA detection is completed by sandwich hybridization between probe DNAs and target miRNA with small sample volume (0.5 μL) within 20 min. Fluorescence signals after hybridization were amplified by laminar flow-assisted dendritic amplification (LFDA) using fluorescein isothiocyanate (FITC)-labeled streptavidin (F-SA) and biotinylated anti-streptavidin (B-anti-SA) as amplification reagents. To enhance the sensitivity of on-chip miRNA detection, the hybridization buffer solution was newly optimized with three main components—sodium dodecyl sulfate (SDS), formamide and dextran sulfate—that are known to strongly influence hybridization. An on-chip miRNA detection test in the newly optimized hybridization buffer (0.2% SDS, 5% formamide and 1% dextran sulfate) revealed dramatic increases in both the LFDA signal in the sample channel and the signal-to-background ratio (S/B ratio). Moreover, the LFDA signals in a blank reference channel remained low due to the suppression of non-specific bindings and hybridizations. By changing the hybridization buffer, we obtained an improved limit of detection (LOD) that was 0.045 pM (miRNA-196a) and 0.45 pM (miRNA-331), which are around 30- and 10-fold better than that of when control hybridization buffer was used. The improved performance of our miRNA detection system with short running time and high sensitivity could contribute to future research, including point-of-care diagnostic systems.

Questions surrounding the optical properties of two-dimensional (2D) triangular single gold nanoplates (AuNPs) remain largely unanswered. Herein, a scanning-electron microscopy-correlated single-particle study was conducted to identify polarization-dependent optical properties of AuNPs under dark-field (DF) and differential interference contrast (DIC) microscopy. AuNPs with an aspect ratio of ∼3 showed a single broad DF scattering spectrum without separation of the two dipole and quadrupole resonance modes present in 2D AuNPs. Polarization-sensitive interference properties of the individual AuNPs were revealed through periodic changes in the intensities and types of DIC images obtained. A dipole resonance mode was found to mainly contribute to the polarization-sensitive interference properties of AuNPs. Furthermore, DIC polarization anisotropy allowed us to track the real-time orientation of a dipole resonance mode of a AuNP rotating on a live cell membrane.

The degradation behavior of silk fibroin (SF) is a significant and intriguing subject in the area of archaeological ancient silk research. In the present study, the immunological detection techniques combined with traditional characterization methods, jointly studied the degradation process of SF from Bombyx mori (B. mori) and Antheraea pernyi (A. pernyi) through exposure to alkaline proteinase, α-chymotrypsin, pepsin, and trypsin. Spectroscopic analysis revealed that different enzymes showed similar hydrolysis effects on the secondary structure, but the changes of B. mori SF and A. pernyi SF were mainly reflected in the decrease of β-sheet and the reduction of α-helical structure, respectively. In further research of immunology, two diagnostic antibodies were prepared corresponding to SF of B. mori and A. pernyi, respectively. The enzyme-linked immunosorbent assay (ELISA) and western blot indicated the enzyme-treated SF proteins still exhibited higher immunoreactivity because the epitopes on the surface of SF molecules are retained. Although α-chymotrypsin possesses the most cleavage sites among these enzymes, the α-chymotrypsin-treated SF did not exhibit significant changes in secondary structures and high antibody binding capacity. The results deepen our understanding of the SF degradation process during enzymatic hydrolysis, and show far-reaching guiding significance in trace detection of SF.

Mercury ions as high toxic pollutants have received wide-spread attention because of their poisonousness, persistence and enrichment. To better understand the distribution of mercury species and supplement more detailed toxicological research, it is necessary to develop some methods for monitoring mercury ions with high sensitivity and selectivity. Therefore, a simple rhodol-based highly selective fluorescent probe, RH-Hg, has been developed for monitoring Hg²⁺ with thiocarbamate as the recognition receptor. The probe RH-Hg can quantificationally detect mercury ions in aqueous solution assisted by hydrogen peroxide (H₂O₂), and it can discriminate Hg²⁺ through “naked-eye” observation of the color changes from light orange to dark pink. Finally, the practical applications of the probe RH-Hg in the river water further demonstrated that it will be an effective and economical tool for monitoring the distribution of Hg²⁺ in the environment.

This paper discusses about the improvement of electrochemical characteristics of graphite paste electrode chemically modified with chitosan through physical crosslinking of the biopolymer with sodium tripolyphosphate. Biopolymer characterizations were performed by scanning electron microscopy, Fourier transform infrared spectroscopy, cyclic voltammetry and electrochemical impedance spectroscopy. The electrochemical characterization of Pb with graphite paste electrode modified with chitosan crosslinked with sodium tripolyphosphate (GPE-CTS-TPP) showed that the process is quasireversible, controlled by adsorption and involves the transfer of two electrons. Additionally, the physical crosslinking process decreased the electrode resistance as well as improved the electron transfer rate. Once the GPE-CTS-TPP showed enhanced morphological and electrochemical characteristics, it was applied for Pb determination by square wave anodic stripping voltammetry. The method presented appropriate accuracy (recoveries from 95 to 108% and concordance with comparative method between 90 and 107%), high sensitivity (limit of detection and quantification of Pb were 0.73 and 2.44 μg L⁻¹, respectively) and could be applied to analytical determinations.

Ion composition contained in individual rain droplets provides important information to investigate the chemistry in rain and clouds, but general rain sampling equipment temporally and spatially averages the information. Determination of the SO₄²⁻ concentration in an individual rain droplet was achieved by precipitate production in synthesized acrylamide polymer gel. Concentration of the target ion was calculated from the droplet print diameter and precipitation area measured from digital microscope images. We investigated the effects of the interior electrolyte concentration in the polyacrylamide gel and UV irradiation time on the physical properties of the gel and precipitate formation. The precipitated components were identified by scanning electron microscopy with energy dispersive X-ray analysis. We also clarified the effects of coexisting ions on the reaction between the interior and exterior electrolytes. For actual rainwater, the SO₄²⁻ concentration estimated by this method was in agreement with the results obtained by ion chromatography.

In HPLC analyses of soluble dietary fiber, desalting processes using open, mixed-bed ion-exchange columns are time-consuming and labor-intensive. We developed and validated a simple desalting method using tandem cation/anion exchange SPE cartridges. We found that combining Bond Elut Jr SCX (upstream) and Bond Elut PSA (downstream) cartridges provided adequate desalting of test solutions. The developed method was then validated in an inter-laboratory study. Five test samples were prepared by mixing food matrixes with purified soluble dietary fiber and treated to generate solutions to test the desalting process. These solutions were then analyzed by eight different laboratories. The results demonstrated that the developed method is simple and reliable for desalting samples containing 140 to 945 mg/100 mL of soluble dietary fiber in preparation for HPLC analysis of soluble dietary fiber.

Circular dichroism (CD) is a technique used for conformational studies of peptides and proteins. We studied the specific calibration procedures of CD spectrometers based on procedures specified in the European Pharmacopoeia. We aimed to develop procedures to improve the usability of CD, in addition to reducing adverse effects on users’ health. The use of ethanol instead of 1,4-dioxane as the solvent for isoandrosterone was examined. Both solvents yielded the same maximum value of +3.3 for molar CD. We also studied a two-point calibration method using (1S)-(+)-ammonium 10-camphorsulfonate instead of (1S)-(+)-10-camphorsulfonic acid, which is a hygroscopic compound. Both compounds yielded similar results and the values for (1S)-(+)-ammonium 10-camphorsulfonate of 2.39 ± 0.04 and –4.92 ± 0.06 at 290.5 and 192.5 nm, respectively, were within the criteria defined in the European Pharmacopoeia. The inter-laboratory repeatability was also acceptable. These studies provide specific procedures for calibrating CD spectrometers for drug development.

A polyethylene glycol/citrate mixed solution was fed into a single channel of a Y-type micro-channel on a microchip as an aqueous two-phase system. A phase separation multi-phase flow with a liquid–liquid interface was generated due to a phase transformation. An annular flow, one of the flow types in the phase separation multi-phase flow, was observed through bright-field microscopy. The flow consisted of citrate-rich inner and polyethylene glycol-rich outer phases. We attempted to separate and collect the two phases in the single channel into two separate Y-type channels. When the pressure losses for the separated channels were not very different, we observed symmetric flow in the Y-type channel. When the pressure losses were quite different, the polyethylene glycol-rich phase with higher viscosity was selectively distributed to the separated channel with lower pressure loss. Thus, the polyethylene glycol-rich phase was successfully and intentionally collected from the chosen Y-type channel via the creation of annular flow in the single channel.