We describe the effect of different sized gold and silver nanoparticles on the terbium sensitized fluorescence of deferasirox. It is indicated that silver nanostructures, especially 18 nm Ag nanoparticles (AgNPs), have a remarkable amplifying effect compared to Au nanoparticles. Based on this observation, a highly sensitive and selective method was developed for the determination of deferasirox. Effects of various parameters like AgNPs and Tb3+ concentration and pH of media were investigated. Under the optimal conditions, a calibration curve was plotted as the fluorescence intensities versus the concentration of deferasirox in the range of 0.1 to 200 nmol L−1, and detection limit of 0.03 nmol L−1 was obtained. The method has good linearity, recovery, reproducibility and sensitivity, and was satisfactorily applied for the determination of deferasirox in urine and pharmaceutical samples.
Bioelectronic noses, such as olfactory cell- and receptor-based biosensors, have important applications for biomimetic odorant detection in various fields. Here, a nanoparticle-equipped biosensor was designed to record extracellular potentials from olfactory receptor cells effectively. In this research, a microelectrode array (MEA) was combined with olfactory epitheliums as the olfactory biosensor to record electrophysiological signals of receptor cells in the epitheliums. Zinc nanoparticles (NanoZn) were employed along with the biosensor for different kinds of odorant measurements, which improved the electrophysiological responses to odor molecules. The NanoZn-equipped biosensor showed greater performance, such as a higher sensitivity and a larger signal-to-noise ratio, than that without the nanoparticles. Thus, this approach provided a promising method to improve the detecting performance of biosensors based on olfactory cells and receptors, which would bring broad application prospects for bioelectronic noses in environmental monitoring, food analysis, and healthcare diagnosis.
A simple mixed-micelle mediated extraction was elaborated for the preconcentration and determination of scandium(III) by inductively coupled plasma optical emission spectrometry. Scandium(III) was complexed with Alizarin Red S and cetyltrimethylammonium bromide at pH 3 to form hydrophobic chelates, which could be extracted with Triton X-114 at room temperature (25°C) in the presence of KI as a salting-out electrolyte. The main parameters of the extraction procedure were investigated in regard to the extraction efficiency of scandium(III). Under the optimum conditions, a linear range of 0.5 – 150 ng mL−1 and a detection limit of 0.2 ng mL−1, along with a preconcentration factor of 100, were achieved. Furthermore, the interference of diverse ions accompanying scandium(III) was extensively studied. The obtained results indicate the high selectivity of the proposed procedure. The accuracy of the procedure was verified through recovery experiments on spiked water samples and synthetic mixtures. The procedure was successfully applied to a scandium(III) determination in clay samples.
A simple potentiometric method for determining the free acidity without complexation in the presence of hydrolysable metal ions and sequentially determining the plutonium concentration by a direct spectrophotometric method using a single aliquot was developed. Interference from the major fission products, which are susceptible to hydrolysis at lower acidities, had been investigated in the free acidity measurement. This method is applicable for determining the free acidity over a wide range of nitric acid concentrations as well as the plutonium concentration in the irradiated fuel solution prior to solvent extraction. Since no complexing agent is introduced during the measurement of the free acidity, the purification step is eliminated during the plutonium estimation, and the resultant analytical waste is free from corrosive chemicals and any complexing agent. Hence, uranium and plutonium can be easily recovered from analytical waste by the conventional solvent extraction method. The error involved in determining the free acidity and plutonium is within ±1% and thus this method is superior to the complexation method for routine analysis of plant samples and is also amenable for remote analysis.
A new method was developed for the determination of eight earthy-musty compounds in drinking water by gas chromatography tandem mass spectrometry (GC-MS/MS) combined with dispersive liquid–liquid microextraction (DLLME). In this work, the type and volume of extraction solvent and dispersion agent, and the amount of NaCl were optimized; the linearity, detection limit, recovery and precision of method were investigated. The results indicated that the target analytes were in the range of 0.2 – 100 μg/L with correlation coefficient (r) ranging from 0.9991 to 0.9999, the limit of detection (LOD, S/N = 3) of the analytes ranged from 0.2 to 1.0 ng/L with the enrichment factor of 320. The mean recoveries for drinking water at three spiked concentrations levels of 0.6 – 32 ng/L were in the range of 91.3 to 103%, the precision ranged from 3.1 to 7.5% (n = 6), and the inter-day precision was from 6.1 to 11.1% (n = 5). Only one of 15 selected real samples tested positive for GSM, and the concentration was 3 ng/L. This method was confirmed to be simple, fast, efficient, and accurate for the determination of earthy-musty compounds in aqueous samples.
One of the quality indicators for honey is 5-(hydroxymethyl)-2-furaldehyde (HMF), which is formed during the heating or aging of honey. The International Honey Commission recommends three methods for the determination of HMF in honey: the Winkler method, the White method, and determination by HPLC. The Winkler method uses the carcinogenic substance p-toluidine, which is not in accordance with the principles of Green Chemistry. The present work describes the determination of HMF in honey by flow injection analysis (FIA) using a modified Winkler method, replacing p-toluidine with p-aminobenzoic acid. The linear range was 1.00 to 40.0 mg L−1, the limit of detection (LOD) was 0.43 mg L−1, and the limit of quantification (LOQ) was 1.32 mg L−1. The method is an efficient and environmentally friendly technique for the analysis of HMF in honey.
The dopamine level in the brain and the mesolimbick dopaminergic system are responsible for nicotine addiction. In the present study, extracellular dopamine in nucleus accumbens was collected by a brain microdialysis technique. Also a sensitive high-performance liquid chromatography–tandem mass spectrometry (HPLC-MS/MS) method with a gradient elution procedure was developed for a precise determination of dopamine in brain dialysate. The retention time of dopamine was about 11.32 min. The linear range was 20 – 1000 pg/mL. The limit of detection (LOD) and the limit of qualification (LOQ) were 5 and 20 pg/mL, respectively. The recovery ranged from 98.2 to 109.0%, and both the intra-RSD and inter-RSD were below <9%, respectively. The probe recovery for dopamine in this brain microdialysis experiment was about 25%. Finally, the dopamine concentrations in the rat brain microdialysates were determined, and the pharmacokinetics of extracellular dopamine in the brain nucleus accumbens after an intravenous injection of nicotine was successfully evaluated.
Near-infrared laser-induced temperature elevation in single aqueous ammonium sulfate droplets levitated in air were evaluated by means of laser trapping and Raman spectroscopy. Since the vapor pressure in an aqueous solution droplet should be thermodynamically in equilibrium with that of water in air, the equilibrium size of the droplet varies sensitively through evaporation/condensation of water in accordance with the temperature change of the droplet. In this study, we demonstrated that the changes in the size of an optically levitated aqueous ammonium sulfate droplet were induced by irradiation of a 1064-nm laser beam as a heat source under an optical microscope. Temperature elevation in the droplet was evaluated successfully by means of Raman spectroscopy, and the values determined were shown to be in good agreement with those by the theoretical calculations based on the absorption coefficient of water at 1064-nm and the thermal conductivity of air. To the best of our knowledge, this is the first experimental demonstration showing that the absorption coefficient evaluated from changes in the size of optically-trapped aqueous droplets is consistent with that of pure water.
This paper presents a sensitive and convenient visual methodology for Salmonella typhimurium detection using gold nanoparticles (AuNPs) as colorimetric probes and magnetic nanoparticles (MNPs) as concentration elements. In the protocol, the aptamers were first immobilized onto the surface of AuNPs and MNPs, respectively. Then, S. typhimurium were added into the above solution and incubated for 45 min. During the incubation, aptamer on the surface of nanoparticles could specifically bind to the target and form a MNPs-aptamer-S. typhimurium-aptamer-AuNPs sandwich structure complex. In a magnetic field, the formed complexes were easily separated from the solution, resulting in a fading of the AuNPs suspension and a decrease of the ultraviolet visible (UV/Vis) signal. The assay shows a linear response toward S. typhimurium concentration through a range of 25 to 105 cfu/mL, and the detection limit was improved to 10 cfu/mL. The applicability of the bioassay in real food samples was also investigated; the results were consistent with the experimental results obtained from plate-counting methods. It is believed that the developed aptasensor will broaden the application in bioassays.
A gas-tight pH measurement is needed to monitor water chemistry at a CO2 geological storage site. In the CO2 reservoirs, the temperature and pressure are generally more than the critical point of CO2 (31.2°C and 7.38 MPa). In this study, a colorimetric pH measurement method was examined up to 20 MPa for future application to various CO2 reservoirs. A mixture of two color indicators, bromocresol green (BCG) and metacresol purple (mCP), was considered to be a suitable measurement method between pH 3 and 9. The uncertainty up to 20 MPa was less than 0.12 pH units without any correction of pressure effects. We demonstrated a pH measurement of formation water at the Nagaoka CO2 post-injection site. The pH measurement was successfully accomplished under a high-pressure condition (ca. 11 MPa) and without degassing of CO2.
The electrochemiluminescence (ECL) of tris(2,2′-bipyridyl)ruthenium(II) (Ru(bpy)32+) is studied in non-aqueous media using dehydroascorbic acid (DHA) as coreactant to validate the evidence for the mechanism of the ascorbic acid (H2A)/Ru(bpy)32+ ECL system in an aqueous media. DHA is electrochemically reduced around –1.2 V vs. Ag/Ag+ in pure acetonitrile to generate the ascorbyl radical anion (A•−), which is confirmed by in-situ UV-visible absorption measurements using a thin-layer spectroelectrochemical cell. The ECL of the DHA/Ru(bpy)32+ system in non-aqueous media is not observed in the potential range from 0 to +1.4 V in anodic potential sweep mode; however, distinct ECL is detected using double potential step electrolysis from –1.2 to +1.4 V vs. Ag/Ag+. The ECL may be generated by a homogeneous charge-transfer process between A•− produced during the first pulse potential step (–1.2 V) and Ru(bpy)33+ generated during the second pulse potential step (+1.4 V). The calculated standard enthalpy (–ΔH°) for the charge-transfer reaction between A•− and Ru(bpy)33+ is 2.29 eV, which is larger than the lowest excited singlet state energy of Ru(bpy)32+ (*Ru(bpy)32+; 2.03 eV, 610 nm). It is determined that the generated intermediate A•− is crucial in the Ru(bpy)32+ ECL reaction.
Selective concentration of ultra-trace components in air-like gases has an important application in analyzing volatile organic compounds in the gas. In the present study, we examined quench-condensation of the sample gas on a ZnO substrate below 50 K followed by temperature programmed desorption (TPD) (low temperature TPD) as a selective gas concentration technique. We studied two specific gases in the normal air; krypton as an inert gas and acetone as a reactive gas. We evaluated the relationship between the operating condition of low temperature TPD and the lowest detection limit. In the case of krypton, we observed the selective concentration by exposing at 6 K followed by thermal desorption at about 60 K. On the other hand, no selectivity appeared for acetone although trace acetone was successfully concentrated. This is likely due to the solvent effect by a major component in the air, which is suggested to be water. We suggest that pre-condensation to remove the water component may improve the selectivity in the trace acetone analysis by low temperature TPD.
When mixed solvent solutions, such as ternary water–hydrophilic/hydrophobic organic solvents, water–surfactant, and water–ionic liquid, are delivered into a microspace under laminar flow conditions, the solvent molecules radially distribute in the microspace, generating inner and outer phases. This specific fluidic behavior is termed “tube radial distribution phenomenon”, and has been used in separation technologies such as chromatography and extraction. The factors influencing the configuration of the inner and outer phases in “tube radial distribution phenomenon” using the above-mentioned mixed solvent solutions were considered from the viewpoint of viscous dissipation in fluidic flows. When the difference in the viscosity between the two phases was large (approximately >0.73 mPa·s), the phase with the higher viscosity formed as an inner phase regardless of the volume ratio. The distribution pattern of the solvents was supported by the viscous dissipation principle. Contrarily, when the difference was small (approximately <0.49 mPa·s), the phase with the larger volume formed as the inner phase. The distribution pattern of the solvents did not always correspond to the viscous dissipation principle. The current findings are expected to be useful in analytical science including microflow analysis research.
Fullerene (C60) changes to its anion radical (C60•−) in the presence of tetraphenylborate (TPB−) under visible-light illumination. Using voltammetry at a liquid/liquid interface, we investigated the electron transfer (ET) between C60•−, previously prepared based on this photochemical reaction, in a nitrobenzene (NB) solution and hexacyanoferrate(III) ([Fe(CN)6]3−) or proton in an aqueous solution. We suggest that positive currents appearing in voltammograms are due to the ion transfer of decomposition products of TPB− and ET from C60•− in the NB phase to [Fe(CN)6]3−, or proton in the W phase. 11B NMR revealed that TPB− decomposed to some borate anions during the photochemical reaction of fullerene. Furthermore, when the NB solution containing C60•− was mixed with an aqueous solution containing [Fe(CN)6]3− or proton, absorption bands of C60•− in a visible/near infrared absorption spectrum disappeared. This disappearance supports the ET across the NB/W interface. This finding is significant as both an example of ET at a liquid/liquid interface including photochemical reactions and the photochemistry of C60.
We report on a biosensor for cocaine based on the conformation change of DNA aptamer by capturing the cocaine molecules. The oxidation current of ferrocene conjugated on the terminal end of aptamer immobilized on an Au electrode increased with increasing cocaine concentration. The sensor response has been improved by a simple heat treatment after immobilization, since the aggregates of DNA aptamer generated during the immobilization step could be dissociated and rearranged on the electrode.
Non-alcoholic steatohepatitis (NASH) can be complicated with chronic kidney disease (CKD). In this study, changes in the distribution of biomolecules in the kidney were studied in NASH model mice with the use of imaging mass spectrometry (IMS). The mass spectra and ion images of IMS showed that the signals of cardiolipin (CL) species were decreased in the kidney cortex of the NASH mice. The decrease of CL might therefore suggest the kidney involvement of NASH.
A new, high-performance, highly practical, simple reagent called alkyl diamide amine (ADAAM) was examined for the separation of Am(III) and Eu(III). ADAAM has three donor atoms, one soft N-donor atom and two hard O-donor atoms, on a central frame. The combination of soft and hard donor atoms affords a tridentate that ensures remarkable extraction ability and selectivity of Am(III) and Eu(III) from highly acidic media (1.5 M HNO3) with a separation factor up to 25.