研究者詳細 - 金田　隆

論文 - 金田　隆

分割表示 133 件中 21 - 40 件目／全件表示 >>

Simultaneous separation of 17 anions by capillary electrophoresis with the addition of an organic solvent 査読

Kazuki Hata, Noriko Nonaka, Nobuyuki Sato, Takashi Kaneta

ELECTROPHORESIS 2021年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：WILEY

Seventeen inorganic and organic anions, that normally are insufficiently separated via ion chromatography, were completely separated by the addition of an organic solvent to a solution of BGE combined with an adjustment of the apparent pH via CE in combination with indirect UV absorbance detection. Methanol, ethanol, and acetonitrile were examined for their utility in manipulating the selective separation of anions. Methanol and acetonitrile were better modifiers than ethanol at enhancing the resolution of anions comigrating in an aqueous solution of BGE. Methanol was selected as the modifier that provided the largest separation window that could achieve a complete separation of the target analytes. Via the use of methanol, manipulation of the selectivity between inorganic anions and that between inorganic and organic anions was enhanced, but the separation between organic anions remained difficult when only methanol was used. By varying the apparent pH of the BGE in the presence of 10% v/v methanol, however, the separation selectivity between organic anions was substantially improved. Eventually, 7 inorganic and 10 organic anions were simultaneously separated using BGE at a pH of 6.3 in the presence of 10% v/v methanol.

DOI： 10.1002/elps.202100014

Indirect capillary electrophoresis immunoassay of membrane protein in extracellular vesicles 査読

Yumeki Tani, Takashi Kaneta

JOURNAL OF CHROMATOGRAPHY A 1629 2020年10月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER

Extracellular vesicles (EVs) exist in biological fluids such as blood, urine, and cerebrospinal fluid, and these have shown promise for use as biomarkers of cancers. Conventional methods for determination of EVs include direct detection via enzyme-linked immunosorbent assay and detection of their membrane proteins via western blotting. These techniques, however, have individual shortcomings in terms of the need for large sample consumption, processes that are time-consuming, and a lack of the capacity for quantification. In this study, we developed a method to determine the EV membrane protein, CD63, by coupling capillary electrophoresis immunoassay with laser-induced fluorescence (CEIA-LIF). In this process, the EVs were isolated from a culture medium and were subsequently reacted with a fluorescently labeled anti-CD63 antibody to form a CD63 complex localized on the surface of EVs. After removing the EVs containing the CD63 immune complex by centrifugation, the supernatant containing the free fluorescent antibody was injected into a capillary to serve as a sample. A decrease in the peak area of the free fluorescent antibody became apparent when the amount of EVs was increased while that of the fluorescent antibody remained constant. The peak areas were decreased proportionally against the increased amounts of EVs. The concentration of the CD63 could then be estimated based on the slope of the linear relationship. This study is the first to quantify CD63 immobilized on EVs via CEIA-LIF, which is a novel method with the potential to determine membrane proteins localized on the surface of EVs. (c) 2020 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.chroma.2020.461513

On-site analysis of paraquat using a completely portable photometric detector operated with small, rechargeable batteries 査読

Sasikarn Seetasang, Takashi Kaneta

ANALYTICA CHIMICA ACTA 1135 99 - 106 2020年10月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER

This work describes a methodology that can be used to achieve on-site analysis of paraquat in water samples by using a miniaturized portable photometer consisting of a couple of light-emitting diodes (LEDs). Paraquat produces a colored radical via a redox reaction with sodium dithionite, which is unstable against oxygen in solution. The steps taken to stabilize the reagent solution included control of the pH and the addition of organic solvents, but the most effective was the formation of an oil layer. Together, these steps stabilized the reagent solution for two days. An increase in the duration of reagent stability, however, is necessary in order to transport the reagent for on-site applications in remote locales. For the time being, an excess amount of solid sodium dithionite can be added directly to sample solutions because the unreacted dithionite shows no influence on absorbance of the paraquat radical. Orange LEDs with a maximum emission wavelength of 609 nm were employed in the portable photometer to measure the absorbance of paraquat radical produced by a redox reaction that has an absorption maximum of 603 nm. The developed photometer showed excellent performance with a linear range of from 2.0 mg L-1 to 40.0 mg L-1 and a linear regression (r(2) = 1). The limits of detection and quantification were 0.5 mg L-1 and 1.5 mg L-1, respectively, intra-day precision (n = 3) and inter-day precision (n = 5) were both less than 5%, and accuracy based on the percentage of sample recovery ranged from 89 +/- 0 to 105 +/- 0% (n = 3). The proposed method was applied to the analysis of paraquat in water samples taken from rice fields. The results showed no paraquat in all thirteen samples, which could have been due to strong adsorption of paraquat by soil particles and/or to complications with the sampling conditions. To confirm the adsorption onto soil of paraquat contained in water, we constructed an artificial rice field where water containing paraquat was impounded above the soil layer. The results showed that paraquat in water gradually decreased within three days and could be measured in the soil on the fourth day. These results were confirmed by HPLC analysis, which underscores the utility of this portable photometer for the on-site monitoring of paraquat in water samples. (C) 2020 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.aca.2020.08.051

Biological pretreatment of carbonaceous matter in double refractory gold ores: A review and some future considerations 査読

Kojo T. Konadu, Diego M. Mendoza, Robert J. Huddy, Susan T. L. Harrison, Takashi Kaneta, Keiko Sasaki

HYDROMETALLURGY 196 2020年9月

記述言語：英語出版者・発行元：ELSEVIER

The pretreatment of carbonaceous material in double refractory gold ores (DRGO) is necessary to decrease pregrobbing of gold and maximize gold recovery. DRGO contains of carbonaceous matter and gold grains encapsulated in sulfide minerals, which typically results in very poor gold recovery. However, there is growing interest in DRGO because some estimates show that it makes up about a third of the total available gold for production by mining. This can be achieved by chemical and biological techniques, however, the chemical techniques like flotation, surface passivation and chemical oxidation have received more extensive study and either have to be retooled or modified to be applied to the carbonaceous matter in the DRGO. In comparison, the biological techniques are relatively unknown with significant gaps in the knowledge about the bio-treatment mechanism, byproducts and avenues for scaling up like bioreactor design. This study reviews the enzymatic pretreatment of DRGO to facilitate gold recovery and minimize reagent consumption. It focuses on the potential for application of oxidative enzymes like lignin peroxidase, manganese peroxidase and laccase to pretreat carbonaceous matter in DRGO with or without an additional step of sulfide oxidation and addresses characterization of byproducts of the enzymatic decomposition. Further, potential bioreactor configurations for the enzymatic decomposition without direct contact of ore with microorganisms are considered, both in terms of understanding the mechanisms within the pretreatment and in terms of application.

DOI： 10.1016/j.hydromet.2020.105434

Direct counting of exosomes in a cell culture medium using neither isolation nor preconcentration 査読

Tatsuya Fujii, Takashi Kaneta

ANALYTICA CHIMICA ACTA 1119 35 - 40 2020年7月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER

Exosomes are expected to be biomarkers of cancer since they contain information about the cells that excrete them. In this study we developed a method to count the exosomes secreted from cancer cells in a culture medium without the need for isolation and/or preconcentration. This detection system consists of a square capillary on which a laser beam is focused in a sheet shape via the use of two cylindrical lenses. A fluorescently labeled anti-CD63 antibody is used to mark the exosomes that are then flowed into the square capillary. In this study, individual exosomes were observed on a trajectory when passing through the laser beam sheet and were counted for 10 min at a constant flow velocity. The total analysis time was less than 1.5 h including the steps required to remove large particles and allow reaction with the antibody. The results for two samples prepared with and without the isolation of exosomes showed a loss of exosomes in the isolation step. We also determined the number of the exosomes secreted by the cells to a culture medium during cultivation. As expected, the total number of exosomes in a culture medium increased with an increase in the cultivation time, and the number of exosomes released every 12 h either remained constant or showed no more than a slight increase for as long as 72 h. It was unclear whether the number exosomes was dependent on the cell population at confluences of 10-60%. (C) 2020 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.aca.2020.04.052

Coalescence of Oil Droplets and Collection of Vesicles by Optical Pressure 査読

Yumeki Tani, Takashi Kaneta

BUNSEKI KAGAKU 69 ( 12 ) 665 - 672 2020年

担当区分：責任著者記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：JAPAN SOC ANALYTICAL CHEMISTRY

We demonstrated the utility of optical pressure in the manipulation of oil droplets and vesicles in the field of analytical chemistry. In order to realize chemical analysis in a limited small space, a method to capture and coalesce two oil droplets was developed using two laser beams. Three types of stabilizers for the formation of oil droplets were explored to achieve the coalescence of two droplets whereas polyethylene glycol (PEG) was the most suitable one among them. When using the oil droplets with PEG, the increase in temperature of the medium induced successful coalescence of two droplets. We also developed a method to collect liposomes, which are a model of artificial extracellular vesicles, using optical pressure. It was found that the collection efficiency was significantly improved by adding gold nanoparticles into the solution. This effect is due to thermal convection induced by the optical absorption of gold nanoparticles in solution and an enhancement of the optical pressure caused by binding between the vesicles and the gold nanoparticles. It was also elucidated that the binding was strongly related to the electrostatic interaction in addition to the hydrophobic interaction. Based on these findings, we achieved the collection of nanometer-sized vesicles and exosomes released by cells by optical pressure.

Chromium speciation using paper-based analytical devices by direct determination and with electromembrane microextraction 査読

Waleed Alahmad, Puttaruksa Varanusupakul, Takashi Kaneta, Pakorn Varanusupakul

ANALYTICA CHIMICA ACTA 1085 98 - 106 2019年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER

In this study, we developed and compared three different methods for chromium speciation in water samples using microfluidic paper-based analytical devices (mu PADs). In all methods, detection was based on the complexation reaction of Cr(VI) with diphenylcarbazide on the mu PADs. Cr(III) ions were oxidized to Cr(VI) by Ce(IV) prior to colorimetric detection on the RADs. In the first method, oxidization of Cr(III) to Cr(VI) in the solution containing both trivalent and hexavalent chromium was performed using a batch procedure to obtain total chromium. A dual electromembrane extraction (DEME) technique for simultaneous preconcentration and extraction of chromium species and a single electromembrane extraction (SEME) for preconcentration and extraction of Cr(VI)/total chromium [quantified as Cr(VI) content after oxidation of Cr(III) ions to Cr(VI)] were used in the second and third methods, respectively. The electromembrane extraction was based on the electrokinetic migration of cationic Cr(III) and anionic Cr(VI) toward the cathode and anode, respectively, into the two different hollow fibres. Octanol-1 and bis(2-ethylhexyl) phosphate (DEHP) in octanol-1 (0.7% v/v) were the most suitable supported liquid membranes for extraction of Cr(VI) and Cr(III), respectively. Among these methods, SEME showed the lowest limits of detection for both analytes.Under optimized conditions, linear calibrations were obtained for Cr(III) from 3 to 30 mu g L-1 and for Cr(VI) from 3 to 70 mu g L-1. The detection limits were 1.0 mu g L-1 and 0.7 mu g L-1 for Cr(III) and Cr(VI), respectively. Our developed method was applied to analyse water samples spiked with different concentrations of Cr(III) and Cr(VI) at the parts-per-billion (ppb) level. The statistical evaluation showed that the proposed method agreed well with the validation method, i.e., inductively coupled plasma atomic emission spectroscopy (ICP-AES). (C) 2019 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.aca.2019.08.002

Development of a miniaturized photometer with paired emitter-detector light-emitting diodes for investigating thiocyanate levels in the saliva of smokers and non-smokers 査読

Sasikarn Seetasang, Takashi Kaneta

TALANTA 204 586 - 591 2019年11月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER

A simple, small and inexpensive photometer that uses a pair of light-emitting diodes (LEDs) and a simple operational amplifier was developed for investigating thiocyanate levels in saliva obtained from smokers and nonsmokers. The photometer is based on paired emitter-detector diodes (PEDDs), and the entire system can be purchased for less than a hundred US dollars. The PEDD-based photometer can measure the transmittance of a solution in a 1-cm disposable polystyrene cuvette using only rechargeable dry-cell batteries, which makes it suitable for analysis outside of equipped laboratories. The metal complex formation between Fe (III) and thiocyanate ions in an acidic condition permits colorimetric detection of thiocyanate ions using LEDs emitting at 465 nm, because the complex shows maximum absorption at 457 nm. The developed photometer exhibits excellent performance with linearity ranging from 0.05 mmol L-1 to 0.75 mmol L-1 and a correlation coefficient (r(2)) > 0.999. The limits of detection and quantification were 0.01 mmol L-1 and 0.05 mmol L-1, respectively. Both intra-and inter-day precision were obtained with relative standard deviations (RSD) of less than 1% in the determination of thiocyanate. The proposed method is simple, facile, and sensitive enough to investigate the levels of thiocyanate in the saliva samples of smokers and non-smokers with centrifugation being the only special treatment for samples. The results showed that the concentrations of thiocyanate were approximately 5-fold higher in smokers than in non-smokers.

DOI： 10.1016/j.talanta.2019.06.024

Characterization of Pieces of Paper That Form Reagent Containers for Use as Portable Analytical Devices 査読

Supatana Buking, Yusuke Suedomi, Duangjai Nacapricha, Takashi Kaneta

ACS OMEGA 4 ( 12 ) 15249 - 15254 2019年9月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER CHEMICAL SOC

Reagent-deposited pieces of paper were characterized by the use of a compact conductometer, a compact pH sensor, and a conventional spectrophotometer to assess their suitability for use as reagent containers. The pieces of paper were fabricated by wax printing to form a limited hydrophilic area to which a consistent volume of an aqueous reagent could be added. The pieces of paper without the reagent increased the conductivity of water gradually because of the release of sodium salts, whereas pH of NaOH decreased because of the acidity of the functional groups in the paper. Three reagents, sulfamic acid as an acid, Na2CO3 as a base, and BaCl2 as a metal salt, were deposited on the pieces of paper to evaluate their ability to release from the pieces of paper. Sulfamic acid and Na2CO3 were released in quantities of 58 and 73% into water after 420 s, whereas 100% of BaCl2 was released after 480 s. The conductometric titrations of NaOH, HCl, and Na2SO4, and the spectrophotometry of Fe2+ were examined using the pieces of paper that contained sulfamic acid, Na2CO3, BaCl2, and 1,10-phenanthroline. Titrations using the pieces of paper suggested that the reagents were quantitatively released into the titrant, which resulted in a linear relationship between the endpoints and the equivalent points. In 120 s of soaking time, 60-70% of the reagents were released. The spectrophotometric measurements of Fe2+ indicated that when an excess amount of the reagents was deposited onto the pieces of paper, they nonetheless sufficiently fulfilled the role of a reagent container.

DOI： 10.1021/acsomega.9b02226

Long-term stabilization of hydrogen peroxide by poly(vinyl alcohol) on paper-based analytical devices 査読

Tuchpongpuch Boonpoempoon, Wanida Wonsawat, Takashi Kaneta

SCIENTIFIC REPORTS 9 2019年9月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：NATURE PUBLISHING GROUP

Stabilizing reagents that can be deposited onto paper is an important issue for researchers who depend on paper-based analytical devices (PADs), because long-term stability of the devices is essential in pointof-care testing. Here, we found that poly(vinyl alcohol) (PVA) would stabilize hydrogen peroxide placed on a paper substrate following exposure to air. Horseradish peroxidase was employed as a sample in colorimetric measurements of PADs after hydrogen peroxide and 3,3',5,5'-tetramethylbenzidine were deposited as substrates in an enzymatic reaction. The addition of PVA to hydrogen peroxide significantly suppressed its degradation. Concentrations of PVA that ranged from 0.5 to 2%, increased the duration of the stability of hydrogen peroxide, and the results for a PVA concentration of 1% approximated those of 2% PVA. Storage of the PADs at 4 degrees C in a refrigerator extended the stability of the hydrogen peroxide containing 2% PVA by as much as 30 days. The stability of hydrogen peroxide without PVA was degraded after one day under room temperature.

DOI： 10.1038/s41598-019-49393-6

Miniaturized Potentiometric Titration for Improving Portability and Accuracy in the Determination of Total Acid in Squeezed Fruit Juice 査読

Thitaporn Sonsa-ard, Duangjai Nacapricha, Takashi Kaneta

JOURNAL OF FOOD SCIENCE 84 ( 8 ) 2165 - 2170 2019年8月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：WILEY

To determine the total acidity in freshly squeezed fruit juice, we miniaturized the potentiometric titrations and achieved better accuracy compared with titrations from a conventional pH probe. The improvement was the result of a higher jump in pH at the endpoint due to a reduction in the dilutions of both the titrand and titrant. A conventional pH probe requires more than 50 mL of titrand, which can lead to a 25000-fold dilution of the titrant when adding the titrant at 2 mu L intervals. Conversely, when the volume of the titrand can be reduced to 1 mL, the dilution is only 500-fold, which results in a higher jump in pH at the endpoint. The concentration of the titrant, NaOH, was optimized by titrating sample solutions containing 25 and 50 mM of citric acid. The addition of 5 M NaOH in intervals of 2 mu L led to a more accurate endpoint for both 25 and 50 mM citric acid solutions. Miniaturization of the titration process is advantageous in terms of portability, accuracy, and in requiring less consumption of a sample, thereby simplifying the process of repeat measurements that are helpful in evaluating the precision of analytical results. Practical samples of squeezed fruit juices were titrated via three methods that showed no significant differences: classic titrimetry with an indicator, conventional potentiometry, and miniaturized potentiometry. This process would be effective for use in the field and in developing countries. Practical Application The total acidity of fruits and fruit juices is an important indicator of quality and is generally expressed in terms of the citric acid content. However, a standard potentiometric titration requires a large sample volume, which makes it difficult to assess dispersion of the acidity for individual fruits. The results of this study indicate that the use of miniaturized potentiometric titration could benefit food chemistry in many developing countries in addition to opening new fields of food chemistry such as on-site quality control of citrus fruit and evaluation of variations in quality.

DOI： 10.1111/1750-3841.14721

Enhancement of optical force acting on vesicles via the binding of gold nanoparticles 査読

Yumeki Tani, Takashi Kaneta

ROYAL SOCIETY OPEN SCIENCE 6 ( 5 ) 190293 2019年5月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ROYAL SOC

Here we found that gold nanoparticles (AuNPs) enhance the optical force acting on vesicles prepared from phospholipids via hydrophobic and electrostatic interactions. A laser beam was introduced into a cuvette filled with a suspension of vesicles and it accelerated them in its propagation direction via a scattering force. The addition of the AuNPs exponentially increased the velocity of the vesicles as their concentration increased, but polystyrene particles had no significant impact on velocity in the presence of AuNPs. To elucidate the mechanism of the increased velocity, the surface charges in the vesicles and the AuNPs were controlled; the surface charges of the vesicles were varied via the use of anionic, cationic and neutral phospholipids, whereas AuNPs with positive and negative charges were synthesized by coating with citrate ion and 4-dimethylaminopyridine, respectively. All vesicles increased the velocity at different degrees depending on the surface charge. The vesicles were accelerated more efficiently when their charges were opposite those of the AuNPs. These results suggested that hydrophobic and electrostatic interactions between the vesicles and the AuNPs enhanced the optical force. By accounting for the binding constant between the vesicles and the AuNPs, we proposed a model for the relationship between the concentration of the AuNPs and the velocity of the vesicles. Consequently, the increased velocity of the vesicles was attributed to the light scattering that was enhanced when AuNPs were adsorbed onto the vesicles.

DOI： 10.1098/rsos.190293

Laser-Induced Fluorometry for Capillary Electrophoresis 招待査読

Takashi Kaneta

CHEMICAL RECORD 19 ( 2-3 ) 452 - 461 2019年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：WILEY-V C H VERLAG GMBH

Laser-induced fluorometry (LIF) has achieved the detection of single molecules, which ranks it among the most sensitive of detection techniques, whereas capillary electrophoresis (CE) is known as a powerful separation method with resolution that is beyond the reach of many other types of chromatography. Therefore, a coupling of LIF with CE has established an unrivaled analytical technique in terms of sensitivity and resolution. CE-LIF has demonstrated excellent performance in bioanalytical chemistry for the high-resolution separation and highly sensitive detection of DNAs, proteins, and small bioactive molecules. This review describes the CE-LIF methods developed by the author's group that include indirect and direct detection using diode lasers, post-column derivatization, and Hadamard transformation, as well as applications to the binding assays of specific DNA immunoassays of proteins and to the determination of anticancer drugs.

DOI： 10.1002/tcr.201800051

Chromatographic paper-based analytical devices using an oxidized paper substrate 査読

Yuki Hashimoto, Takashi Kaneta

ANALYTICAL METHODS 11 ( 2 ) 179 - 184 2019年1月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ROYAL SOC CHEMISTRY

A novel detection scheme using chromatographic retention was proposed for paper-based analytical devices (PADs). Using a wax printer and an ink-jet printer, the PADs consisted of a straight-flow channel, a circular sample zone, and a band of brilliant green (BG) printed at the connection between the sample zone and the flow channel. When a constant volume of a sample solution was applied to the sample zone, the BG band formed a colored bar along the flow channel that marked the adsorption and desorption of the paper substrate according to the principles of chromatography. If the sample solution contained an anionic complex of boric acid with chromotropic acid, the anionic complex enhanced desorption of the BG from the paper substrate via the formation of an ion-pair with the BG, which resulted in an elongated colored bar. Fundamental equations for the retention behavior of the BG on the PADs were derived using a model based on chromatographic principles and ion-pairing formation. A retardation factor, R-f, was correlated with the concentration of boric acid contained in the sample solutions. To enhance the adsorption of the BG, 2,2,6,6-tetramethylpiperidine 1-oxyl was used to oxidize the paper substrate. The oxidized paper substrate shortened the colored bar of a blank solution and formed a clear boundary for the color. When the analytical conditions were optimized for pH and the concentration of chromotropic acid, the PAD permitted the measurement of boric acid for a concentration ranging from 0.3 to 3 mM. The proposed model was validated when the fitting curve was calculated using the derived equations, which resulted in good agreement with the experimental data.

DOI： 10.1039/c8ay02298d

Microfluidic paper-based analytical devices with instrument-free detection and miniaturized portable detectors 査読

Takashi Kaneta, Waleed Alahmad, Pakorn Varanusupakul

APPLIED SPECTROSCOPY REVIEWS 54 ( 2 ) 117 - 141 2019年

担当区分：責任著者記述言語：英語出版者・発行元：TAYLOR & FRANCIS INC

Microfluidic paper-based analytical devices (mu PADs) have attracted much attention over the past decade because they offer clinicians the ability to deliver point-of-care testing and onsite analysis. Many of the advantages of mu PADs, however, are limited to work in a laboratory setting due to the difficulties of processing data when using electronic devices in the field. This review focuses on the use of mu PADs that have the potential to work without batteries or with only small and portable devices such as smartphones, timers, or miniaturized detectors. The mu PADs that can be operated without batteries are, in general, those that allow the visual judgment of analyte concentrations via readouts that are measured in time, distance, count, or text. Conversely, a smartphone works as a camera to permit the capture and processing of an image that digitizes the color intensity produced by the reaction of an analyte with a colorimetric reagent. Miniaturized detectors for electrochemical, fluorometric, chemiluminescence, and electrochemiluminescence methods are also discussed, although some of them require the use of a laptop computer for operation and data processing.

DOI： 10.1080/05704928.2018.1457045

A colorimetric paper-based analytical device coupled with hollow fiber membrane liquid phase microextraction (HF-LPME) for highly sensitive detection of hexavalent chromium in water samples 査読

Waleed Alahmad, Nuttanee Tungkijanansin, Takashi Kaneta, Pakorn Varanusupakul

TALANTA 190 78 - 84 2018年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE BV

A simple and highly sensitive procedure based on the combination of hollow fiber membrane liquid phase microextraction and a microfluidic paper-based analytical device (mu PAD) was developed for pre-concentration and determination of hexavalent chromium in water samples. The hexavalent chromium was pre-concentrated using the HF-LPME technique via ion exchange or a coupled transport process through a supported ionic liquid (Aliquat 336) prior to colorimetric detection with diphenylcarbazide on the mu PAD. The violet colour could be seen by the naked eye. Images from the mu PADs were scanned using a commercial desktop scanner at 600 dpi resolution. ImageJ software was used for quantitative analysis by measuring the intensity values at green colour channel since it gave the best sensitivity among the RGB colour. Under optimal conditions, the calibration curve was linear in the range 10-90 mu gL(-1), with a limit of detection of 3 mu g L-1. The developed method was successfully applied to determine the level of hexavalent chromium spiked into natural water samples at the parts-per-billion (ppb) level, and the results were in good agreement with those obtained using inductively coupled plasma atomic emission spectroscopy (ICP-AES). The developed method was able to improve the detection limit of the conventional mu PAD, and was expected to be used for the effective analysis of hexavalent chromium in natural water.

DOI： 10.1016/j.talanta.2018.07.056

Hydrophobic assembly of gold nanoparticles into plasmonic oligomers with Langmuir-Blodgett film 査読

Shiho Ikegami, Kenzo Yamaguchi, Takuo Tanaka, Nobuyuki Takeyasu, Takashi Kaneta

JAPANESE JOURNAL OF APPLIED PHYSICS 57 ( 12 ) 2018年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：IOP PUBLISHING LTD

Hydrophobic effect was utilized to self-assemble gold nanoparticles into oligomer structures, or plasmonic dimers, trimers, and so on. Langmuir-Blodgett film of n-octadecanamine was prepared on a glass substrate. Citrate-stabilized gold nanoparticles were adsorbed onto the film, resulting hydrophobic point decoration. The gold nanoparticles with the point decoration were removed from the substrate and self-assembled into plasmonic dimers in ethanol. The products were observed by an atomic force microscope, where not only dimers but also trimers and other aggregates were found. The yield of the plasmonic dimer was similar to 13% without any purifications. We measured the scattering spectrum of the single plasmonic dimer, exhibiting the optical anisotropy. (C) 2018 The Japan Society of Applied Physics

DOI： 10.7567/JJAP.57.120311

Enhanced Optical Collection of Micro- and Nanovesicles in the Presence of Gold Nanoparticles 査読

Mai Kuboi, Nobuyuki Takeyasu, Takashi Kaneta

ACS OMEGA 3 ( 3 ) 2527 - 2531 2018年3月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER CHEMICAL SOC

We describe a process for collecting micro- and nanovesicles on a glass substrate using the optical pressure of a laser beam. The laser beam was focused on a glass substrate that sandwiched a solution containing vesicles prepared using a phospholipid. The optical pressure generated at the surface of the vesicles pulled them into the center of the beam where they formed an aggregate on the glass surface. The vesicles prepared with a buffer solution were successfully collected via adsorption onto the glass surface, whereas the vesicles prepared with pure water exhibited no such tendency. The time required to collect a certain amount of vesicles was inversely proportional to their concentration. To enhance the collection efficiency, we added gold nanoparticles to the vesicle solution. The addition of gold nanoparticles into the solution reduced the collection time to one-tenth of that without it, and this was attributed to thermal mixing promoted by the heat generated by the absorption from the gold nanoparticles in the solution, as well as to an enhancement of light scattering induced by the gold nanoparticles. The optical collection of vesicles coupled with gold nanoparticles shows a promise for the collection of trace amounts of extracellular vesicles in biological fluids.

DOI： 10.1021/acsomega.8b00033

Highly Sensitive Paper-based Analytical Devices with the Introduction of a Large Volume Sample via Continuous Flow 査読

Yuhi Shimada, Takashi Kaneta

ANALYTICAL SCIENCES 34 ( 1 ) 65 - 70 2018年1月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：JAPAN SOC ANALYTICAL CHEMISTRY

The implementation of continuous flow in paper-based analytical devices (PADs) was challenging because of the large volume introduction that was created; but this allowed for the development of novel types of PADs for preconcentration, separation, and sensitive detection. In this study, pump-free continuous flow was applied to a distance-based PAD for the determination of iron ions. Continuous flow enabled the introduction of a volume that exceeded what was necessary to fill the hydrophilic channel of a PAD. Thus, this continuous-flow method significantly improved both the limits of detection (LOD) and the limits of quantification (LOQ) for a distance-based PAD by increasing the sample volume that could be introduced into the PAD. The values for LOD and LOQ were 20 and 26 ppb, respectively, which were more than 150-times lower than that obtained using a small sample volume (50 mu L), and were comparable to those of inductively coupled plasma-atomic emission spectrometry. The continuous-flow technique was applicable to the determination of iron ions at levels of several tens of ppb in natural water without preconcentration.

DOI： 10.2116/analsci.34.65

Guest Editorial 査読

Daniel Citterio, Takashi Kaneta

ANALYTICAL SCIENCES 34 ( 1 ) 5 - 6 2018年1月

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