start-ver=1.4 cd-journal=joma no-vol=123 cd-vols= no-issue= article-no= start-page=105627 end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2023 dt-pub=202310 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Fluorometric assay of laccase in mushroom extracts and comparisons with absorption spectrophotometry en-subtitle= kn-subtitle= en-abstract= kn-abstract=Laccase is a lignin-degrading enzyme that is expected to move industrial applications to a greener form of biotechnology. Here, we used 2,2'-azinobis(3-ethylbenzthiazolin-6-sulfonic acid) (ABTS) as a mediator and N-benzoyl leucomethylene blue (BLMB) as a substrate to develop a fluorometric assay that we used to measure laccase activity in mushroom extracts. We then compared this novel approach to conventional absorption spectrophotometry. With this novel approach, laccase oxidizes ABTS to produce ABTS radicals that show an absorption maximum at 415 nm. The ABTS radicals oxidize BLMB to generate fluorescent methylene blue that is measured by fluorometry while absorption spectrophotometry directly measures the absorbance of the ABTS radicals at 415 nm. Under the optimal conditions, the fluorometric assay showed a linear calibration curve with limits of detection and quantification of 1.0 × 10-2 mg mL-1 and 3.2 × 10-2 mg mL-1, respectively, and those values are 1.4-fold lower than the results using conventional absorption spectrophotometry to measure ABTS radicals. Laccase activity of extracts from species of mushrooms that include eryngii and shiitake were successfully determined via both fluorometry and absorption spectrophotometry. The eryngii extract showed the highest level of activity, which was followed by the shiitake extract, but laccase activity was not observed in the shimeji extract. en-copyright= kn-copyright= en-aut-name=RenJianchao en-aut-sei=Ren en-aut-mei=Jianchao kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=DanchanaKaewta en-aut-sei=Danchana en-aut-mei=Kaewta kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=SasakiKeiko en-aut-sei=Sasaki en-aut-mei=Keiko kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=KanetaTakashi en-aut-sei=Kaneta en-aut-mei=Takashi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= affil-num=1 en-affil=Department of Chemistry, Okayama University kn-affil= affil-num=2 en-affil=Department of Chemistry, Okayama University kn-affil= affil-num=3 en-affil=Department of Earth Resources Engineering, Graduate School of Engineering, Kyushu University kn-affil= affil-num=4 en-affil=Department of Chemistry, Okayama University kn-affil= en-keyword=Laccase kn-keyword=Laccase en-keyword=Mushroom kn-keyword=Mushroom en-keyword=Fluorometry kn-keyword=Fluorometry en-keyword=2,2'-Azinobis(3-ethylbenzthiazolin-6-sulfonic acid) kn-keyword=2,2'-Azinobis(3-ethylbenzthiazolin-6-sulfonic acid) en-keyword=N-Benzoyl leucomethylene blue kn-keyword=N-Benzoyl leucomethylene blue END start-ver=1.4 cd-journal=joma no-vol=1706 cd-vols= no-issue= article-no= start-page=464247 end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2023 dt-pub=20230913 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Separation and fractionation of glutamic acid and histidine via origami isoelectric focusing en-subtitle= kn-subtitle= en-abstract= kn-abstract=We demonstrated the fractionation of two amino acids, glutamic acid and histidine, separated via isoelectric focusing (IEF) on filter paper folded and stacked in an origami fashion. Channels for electrophoresis were fabricated as circular zones acquired via wax printing onto the filter paper. An ampholyte solution with amphiphilic samples was deposited on all the circle zones, which was followed by folding to form the electrophoresis channels. IEF was achieved by applying an electrical potential between the anodic and cathodic chambers filled with phosphoric acid and sodium hydroxide solutions, respectively. A pH gradient was formed using either a wide-range ampholyte with a pH of 3 to 10 or a narrow-range version with a pH of 5 to 8, which was confirmed by adding pH indicators to each layer. The origami IEF was used to separate the amino acids, glutamic acid and histidine, by mixing with the ampholytes, which were deposited on the layers. The components in each layer were extracted with water and measured by high-performance liquid chromatography using pre-column derivatization with dansyl chloride. The results indicated that the focus for glutamic acid and that for histidine were at different layers, according to their isoelectric points. The origami isoelectric focusing achieved the fractionation of amino acids in less than 3 min using voltage as low as 30 V. en-copyright= kn-copyright= en-aut-name=DanchanaKaewta en-aut-sei=Danchana en-aut-mei=Kaewta kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=YamashitaNayu en-aut-sei=Yamashita en-aut-mei=Nayu kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=UmedaMika I. en-aut-sei=Umeda en-aut-mei=Mika I. kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=KanetaTakashi en-aut-sei=Kaneta en-aut-mei=Takashi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= affil-num=1 en-affil=Department of Chemistry, Okayama University kn-affil= affil-num=2 en-affil=Department of Chemistry, Okayama University kn-affil= affil-num=3 en-affil=Department of Chemistry, Okayama University kn-affil= affil-num=4 en-affil=Department of Chemistry, Okayama University kn-affil= en-keyword=Paper-based analytical device kn-keyword=Paper-based analytical device en-keyword=Isoelectric focusing kn-keyword=Isoelectric focusing en-keyword=Origami electrophoresis kn-keyword=Origami electrophoresis en-keyword=Amino acids kn-keyword=Amino acids END start-ver=1.4 cd-journal=joma no-vol=8 cd-vols= no-issue=12 article-no= start-page=11213 end-page=11219 dt-received= dt-revised= dt-accepted= dt-pub-year=2023 dt-pub=20230317 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Development of Pipetteless Paper-Based Analytical Devices with a Volume Gauge en-subtitle= kn-subtitle= en-abstract= kn-abstract=In this work, we propose a new design for paper based analytical devices (PADs) that eliminate the need to use a micropipette for sample introduction. With this design, a PAD is equipped with a distance-based detection channel that is connected to a storage channel that indicates the volume of a sample introduced into the PAD. The analyte in the sample solution reacts with a colorimetric reagent deposited into the distance-based detection channel as the sample solution flows into the storage channel where the volume is measured. The ratio of the lengths of the detection channel and that of the storage channel (D/S ratio) are constant for a sample containing a certain concentration, which is independent of the introduced volume. Therefore, the PADs permit volume-independent quantification using a dropper instead of a micropipette because the length of the storage channel plays the role of a volume gauge to estimate the introduced sample volume. In this study, the D/S ratios obtained with a dropper were comparable to those obtained with a micropipette, which confirmed that precise volume control is unnecessary for this PAD system. The proposed PADs were applied to the determinations of iron and bovine serum albumin using bathophenanthroline and tetrabromophenol blue as colorimetric reagents, respectively. The calibration curves showed good linear relationships with coefficients of 0.989 for iron and 0.994 for bovine serum albumin, respectively. en-copyright= kn-copyright= en-aut-name=DanchanaKaewta en-aut-sei=Danchana en-aut-mei=Kaewta kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=IwasakiHiroshi en-aut-sei=Iwasaki en-aut-mei=Hiroshi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=ThayawutthikunYada en-aut-sei=Thayawutthikun en-aut-mei=Yada kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=SaetearPhoonthawee en-aut-sei=Saetear en-aut-mei=Phoonthawee kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= en-aut-name=KanetaTakashi en-aut-sei=Kaneta en-aut-mei=Takashi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=5 ORCID= affil-num=1 en-affil=Department of Chemistry, Okayama University kn-affil= affil-num=2 en-affil=Department of Chemistry, Okayama University kn-affil= affil-num=3 en-affil=Flow Innovation-Research for Science and Technology Laboratories (FIRST Labs), Mahidol University kn-affil= affil-num=4 en-affil=Flow Innovation-Research for Science and Technology Laboratories (FIRST Labs), Mahidol University kn-affil= affil-num=5 en-affil=Department of Chemistry, Okayama University kn-affil= END start-ver=1.4 cd-journal=joma no-vol=39 cd-vols= no-issue=5 article-no= start-page=643 end-page=651 dt-received= dt-revised= dt-accepted= dt-pub-year=2022 dt-pub=20221105 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Optical collection of extracellular vesicles in a culture medium enhanced by interactions with gold nanoparticles en-subtitle= kn-subtitle= en-abstract= kn-abstract=Extracellular vesicles (EVs) exist in biological fluids such as blood, urine, and cerebrospinal fluid and are promising cancer biomarkers. Attempts to isolate and analyze trace EVs, however, have been a challenge for researchers studying their functions and secretion mechanisms, which has stymied the options for diagnostic application. This study demonstrated a collection of EVs that was enhanced by gold nanoparticles (AuNPs) via the use of optical force. The collection system consists of an inverted microscope equipped with a CCD camera, a square capillary connected with a PTFE tube, and an Nd:YAG laser that generates optical force. The laser beam was focused on a capillary wall in which a cell culture medium containing EVs flowed continuously. Control of the surface charges on both the capillary wall and the AuNPs achieved the collection and retention of EVs on the capillary wall. The positively charged capillary wall retained EVs even after the laser irradiation was halted due to the negative charges inherent on the surface of EVs. Conversely, positively charged AuNPs had a strong electrostatic interaction with EVs and enhanced the optical force acting on them, which made collecting them a much more efficient process. en-copyright= kn-copyright= en-aut-name=TaniYumeki en-aut-sei=Tani en-aut-mei=Yumeki kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=OchiaiKenta en-aut-sei=Ochiai en-aut-mei=Kenta kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=KanetaTakashi en-aut-sei=Kaneta en-aut-mei=Takashi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= affil-num=1 en-affil=Department of Chemistry, Okayama University kn-affil= affil-num=2 en-affil=Department of Chemistry, Okayama University kn-affil= affil-num=3 en-affil=Department of Chemistry, Okayama University kn-affil= en-keyword=Optical force kn-keyword=Optical force en-keyword=Extracellular vesicle kn-keyword=Extracellular vesicle en-keyword=exosome kn-keyword=exosome en-keyword=Gold nanoparticle kn-keyword=Gold nanoparticle en-keyword=Optical trapping kn-keyword=Optical trapping END start-ver=1.4 cd-journal=joma no-vol=179 cd-vols= no-issue= article-no= start-page=107513 end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2022 dt-pub=202208 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Determination of glutamate using paper-based microfluidic devices with colorimetric detection for food samples en-subtitle= kn-subtitle= en-abstract= kn-abstract=A paper-based device (PAD) capable of colorimetric detection was developed to determine the presence of glutamate in various food samples. The PAD employs an enzymatic reaction with glutamate followed by an oxidation reaction with N-benzoyl leucomethylene blue (BLMB) in the presence of horseradish peroxidase. The designed PAD consists of a sample introduction zone connected to a channel that transports a sample solution to three detection zones. The detection zones contain pre-deposited reagents: glutamate oxidase, horseradish peroxidase, BLMB, a phosphate buffer, and poly(acrylic acid). The PAD is perpendicularly immersed into a sample solution and bent at a right angle using a 3D-printed holder to allow the sample to simultaneously flow into three different detection zones. When the PAD is immersed into a sample containing glutamate, glutamate oxidase produces hydrogen peroxide, which changes the pale blue color of BLMB to a deep blue color in the presence of horseradish peroxidase. Under the optimum conditions, the calibration curve between the logarithm of the glutamate concentrations and the color intensity was linear within a range of from 5 x 10(-6) mol L-1 to 10(-2) and with a correlation coefficient of 0.994. Using this system, the PAD successfully determined glutamate in soup stocks, sauces, snacks, and tomato juice without the need of complicated sample pretreatment. These results agreed with those of a commercially available glutamate assay kit, which was employed as a certification method (t(stat )= 1.95, t(crit )= 2.57). The developed PAD is simple, easy to fabricate, portable, and could be used outside of equipped laboratories to determine the presence of glutamate in food samples. en-copyright= kn-copyright= en-aut-name=DanchanaKaewta en-aut-sei=Danchana en-aut-mei=Kaewta kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=IwasakiHiroshi en-aut-sei=Iwasaki en-aut-mei=Hiroshi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=OchiaiKenta en-aut-sei=Ochiai en-aut-mei=Kenta kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=NambaHaruka en-aut-sei=Namba en-aut-mei=Haruka kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= en-aut-name=KanetaTakashi en-aut-sei=Kaneta en-aut-mei=Takashi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=5 ORCID= affil-num=1 en-affil=Department of Chemistry, Graduate School of Natural Science and Technology, Okayama University kn-affil= affil-num=2 en-affil=Department of Chemistry, Graduate School of Natural Science and Technology, Okayama University kn-affil= affil-num=3 en-affil=Department of Chemistry, Graduate School of Natural Science and Technology, Okayama University kn-affil= affil-num=4 en-affil=Department of Chemistry, Graduate School of Natural Science and Technology, Okayama University kn-affil= affil-num=5 en-affil=Department of Chemistry, Graduate School of Natural Science and Technology, Okayama University kn-affil= en-keyword=Glutamate kn-keyword=Glutamate en-keyword=Paper-based analytical device kn-keyword=Paper-based analytical device en-keyword=Enzymatic reaction kn-keyword=Enzymatic reaction END start-ver=1.4 cd-journal=joma no-vol=7 cd-vols= no-issue=4 article-no= start-page=1194 end-page=1200 dt-received= dt-revised= dt-accepted= dt-pub-year=2022 dt-pub=2022411 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Dip-and-Read, Organic Solvent-Compatible, Paper-Based Analytical Devices Equipped with Chromatographic Separation for Indole Analysis in Shrimp en-subtitle= kn-subtitle= en-abstract= kn-abstract=We developed an organic solvent-compatible paper-based analytical device (PAD) for the quantitative analysis of indole, which is an indicator of shrimp freshness. Although indole is insoluble in water, ethyl acetate is a suitable solvent to dissolve and extract indole from shrimp. The PADs are fabricated using a cutting method that allows the use of an organic solvent because no hydrophobic barrier is needed to form fluidic channels. Ehrlich's reagent consists of 4-(dimethylamino)benzaldehyde and p-dimethylaminobenzaldehyde and was deposited onto the reaction zone of the PAD followed by lamination to prevent evaporation of the ethyl acetate. Samples are introduced into the PAD via immersion in organic sample solutions. When the PAD is immersed into an indole solution of ethyl acetate in a closed bottle, the sample solution penetrates the channel of the PAD and successively flows into the detection zone to form a hydrophilic colored product. The PADs provide a linear relationship between the logarithm of the indole concentration and the color intensity within a range of 1.0-20 ppm with correlation coefficients of r2 > 0.99. The limits of detection and quantification are 0.36 and 0.71 ppm, respectively. Relative standard deviations for both the intraday (n = 2) and interday (n = 3) precision were less than 2.5%. In the indole analysis of shrimp, the PADs separated the interfering orange-colored astaxanthin in the extract from the colored product of indole via the paper chromatographic principle. We used the PADs to investigate the degradation of shrimp, and the results showed a rapid increase in the indole level after 7 days. High-performance liquid chromatography verified the accuracy of the PADs by showing good agreement with the obtained indole levels. en-copyright= kn-copyright= en-aut-name=SeetasangSasikarn en-aut-sei=Seetasang en-aut-mei=Sasikarn kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=KanetaTakashi en-aut-sei=Kaneta en-aut-mei=Takashi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= affil-num=1 en-affil=Department of Chemistry, Graduate School of Natural Science and Technology, Okayama University kn-affil= affil-num=2 en-affil=Department of Chemistry, Graduate School of Natural Science and Technology, Okayama University kn-affil= en-keyword=Ehrlich’s reagent kn-keyword=Ehrlich’s reagent en-keyword=astaxanthin kn-keyword=astaxanthin en-keyword=chromatography kn-keyword=chromatography en-keyword=indole kn-keyword=indole en-keyword=paper-based device kn-keyword=paper-based device en-keyword=shrimp kn-keyword=shrimp END start-ver=1.4 cd-journal=joma no-vol= cd-vols= no-issue= article-no= start-page= end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2021 dt-pub=2021 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Microfluidic Paper-based Analytical Devices Coupled with Coprecipitation Enrichment Show Improved Trace Analysis of Copper Ions in Water Samples en-subtitle= kn-subtitle= en-abstract= kn-abstract=The present study was focused on improving sensitivity to trace levels of Cu(II) by subjecting microfluidic paper based analytical devices (μ PADs) to a preconcentration process via coprecipitation using aluminum hydroxide. The experimental conditions were optimized for the pH of the coprecipitation, centrifugation, and amounts of reagents that were deposited onto µ PADs for Cu(II) assay. The resultant limit of detection reached as low as 0.003 mg L 1 with a linear range of 0.01 2.00 mg L 1 . The relative standard deviations for intra and inter day precision were 3.2 and 4.6%, respectively (n = 9). Spiked water samples were analyzed using the μ PADs after coprecipitation preconcentration. The results were verified by comparing them with thos e of inductively coupled plasma optical emission spectrometry (ICP OES). Recoveries ranged from 97.1 104% and from 98.7 105% using the present method and ICP OES, respectively. These results suggest that the simple, highly sensitive, and inexpensive propos ed method would be helpful for analyzing trace levels of Cu(II) in water samples in poorly equipped laboratories. en-copyright= kn-copyright= en-aut-name=MUHAMMEDAbdellah en-aut-sei=MUHAMMED en-aut-mei=Abdellah kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=HUSSENAhmed en-aut-sei=HUSSEN en-aut-mei=Ahmed kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=KanetaTakashi en-aut-sei=Kaneta en-aut-mei=Takashi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= affil-num=1 en-affil=Center for Environmental Science, College of Natural and Computational Sciences, Addis Ababa University kn-affil= affil-num=2 en-affil=Center for Environmental Science, College of Natural and Computational Sciences, Addis Ababa University kn-affil= affil-num=3 en-affil=Department of Chemistry, Graduate School of Natural Science and Technology, Okayama University kn-affil= en-keyword=Microfluidic paper based analytical device kn-keyword=Microfluidic paper based analytical device en-keyword=Coprecipitation kn-keyword=Coprecipitation en-keyword=Preconcentration kn-keyword=Preconcentration en-keyword=Aluminum hydroxide kn-keyword=Aluminum hydroxide en-keyword=Copperion kn-keyword=Copperion en-keyword=bathocuproine kn-keyword=bathocuproine END start-ver=1.4 cd-journal=joma no-vol=171 cd-vols= no-issue= article-no= start-page=106777 end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2021 dt-pub=202112 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Portable two-color photometer based on paired light emitter detector diodes and its application to the determination of paraquat and diquat en-subtitle= kn-subtitle= en-abstract= kn-abstract=Here we describe a methodology for the determination of paraquat and diquat using a newly developed portable photometer equipped with two colors of paired light emitter detector diodes (PEDD). The colorimetric measurements employed in this work include the redox reactions between 1) dithiothreitol and diquat to produce the red color characteristic of a diquat radical and 2) between sodium dithionite and either diquat or paraquat that results in the green and blue colors of diquat and paraquat radicals, respectively. The addition of sodium dithionite or dithiothreitol in a solid-state provides reproducible absorbance of the radicals, prevents decomposition of the reagents in a solution, and simplifies handling of the reagents. The diquat radical produced by dithiothreitol (λmax = 495 nm) was successfully detected by using a pair of blue LEDs with a maximum emission wavelength at 472 nm while the radicals of paraquat (λmax = 603 nm) and diquat (λmax = 771 nm) reduced by sodium dithionite were measured by a pair of orange LEDs with a maximum emission wavelength of 609 nm. The proposed method consists of measuring diquat radicals at 472 nm, estimating the absorbance of diquat radicals at 609 nm, and subtracting the estimated absorbance of diquat radicals from the total absorbance at 609 nm to determine paraquat radicals. The developed method yielded examples of excellent linear regression (r2) of more than 0.99 in three calibration curves of the radicals measured at 472 nm for diquat radicals and measured at 609 nm for both diquat and paraquat radicals. The intra-day (n = 3) and inter-day (n = 3) precision of three calibration curves were less than or equal to 5%. By comparison with the standard method of high-performance liquid chromatography, the reliability of the proposed method was proven via the analysis of paraquat and diquat radicals in a commercially available herbicide. en-copyright= kn-copyright= en-aut-name=SeetasangSasikarn en-aut-sei=Seetasang en-aut-mei=Sasikarn kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=KanetaTakashi en-aut-sei=Kaneta en-aut-mei=Takashi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= affil-num=1 en-affil=Department of Chemistry, Graduate School of Natural Science and Technology, Okayama University kn-affil= affil-num=2 en-affil=Department of Chemistry, Graduate School of Natural Science and Technology, Okayama University kn-affil= en-keyword=Diquat kn-keyword=Diquat en-keyword=Dithiothreitol kn-keyword=Dithiothreitol en-keyword=Light-emitting diode kn-keyword=Light-emitting diode en-keyword=Paraquat kn-keyword=Paraquat en-keyword=Photometric detector kn-keyword=Photometric detector en-keyword=Sodium dithionite kn-keyword=Sodium dithionite END start-ver=1.4 cd-journal=joma no-vol=413 cd-vols= no-issue= article-no= start-page=3339 end-page=3347 dt-received= dt-revised= dt-accepted= dt-pub-year=2021 dt-pub=20210313 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Speciation of chromium in water samples using microfluidic paper-based analytical devices with online oxidation of trivalent chromium en-subtitle= kn-subtitle= en-abstract= kn-abstract= Speciation of chromium (Cr) was demonstrated using microfluidic paper-based analytical devices (μ-PADs) that permit the colorimetric determination of hexavalent chromium (Cr(VI)) and trivalent chromium (Cr(III)) via online oxidation. The μ-PADs consist of left and right channels that allow the simultaneous measurements of Cr(VI) and total Cr based on the colorimetric reaction of Cr(VI) with 1,5-diphenylcarbazide (DPC). For the determination of Cr(VI), a sample solution was directly reacted with DPC in the left channels whereas total Cr was determined in the right channels, which permitted online oxidation in the pretreatment zone containing cerium (IV) (Ce(IV)) followed by a colorimetric reaction with DPC. We found that the online oxidation of Cr(III) proceeded 100% whereas Ce(IV) inhibited the reaction of Cr(VI) with DPC. Therefore, speciation can be achieved by measuring the Cr(VI) and total Cr in the left and right channels followed by the subtraction of Cr(VI) from total Cr. The limits of detection and quantification were 0.008 and 0.02 mg L−1 for Cr(VI) and 0.07 and 0.1 mg L−1 for Cr(III) or total Cr, respectively. The linear dynamic ranges were 0.02–100 mg L−1 and 0.1–60 mg L−1 for Cr(VI) and Cr(III), respectively. The RSDs were less than 7.5%. The results obtained using μ-PADs were in good agreement with those obtained via ICP-OES with recoveries of 92–108% for Cr(III) and 108–110% for Cr (VI) using μ-PADs, and 106–110% for total Cr using ICP-OES. Thus, the μ-PADs could potentially be utilized for the speciation of chromium in developing countries where environmental pollution and the availability of sophisticated instruments are significant problems. en-copyright= kn-copyright= en-aut-name=MuhammedAbdellah en-aut-sei=Muhammed en-aut-mei=Abdellah kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=HussenAhmed en-aut-sei=Hussen en-aut-mei=Ahmed kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=KanetaTakashi en-aut-sei=Kaneta en-aut-mei=Takashi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= affil-num=1 en-affil=Center for Environmental Science, College of Natural and Computational Sciences, Addis Ababa University kn-affil= affil-num=2 en-affil=Center for Environmental Science, College of Natural and Computational Sciences, Addis Ababa University kn-affil= affil-num=3 en-affil=Department of Chemistry, Graduate School of Natural Science and Technology, Okayama University kn-affil= en-keyword=Microfluidic paper-based analytical device kn-keyword=Microfluidic paper-based analytical device en-keyword=Chromium kn-keyword=Chromium en-keyword=Cr(III) kn-keyword=Cr(III) en-keyword=Cr(VI) kn-keyword=Cr(VI) en-keyword=Online oxidation kn-keyword=Online oxidation en-keyword=Speciation kn-keyword=Speciation END start-ver=1.4 cd-journal=joma no-vol=1135 cd-vols= no-issue= article-no= start-page=99 end-page=106 dt-received= dt-revised= dt-accepted= dt-pub-year=2020 dt-pub=20200827 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=On-site analysis of paraquat using a completely portable photometric detector operated with small, rechargeable batteries en-subtitle= kn-subtitle= en-abstract= kn-abstract=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 (r2 = 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. en-copyright= kn-copyright= en-aut-name=SeetasangSasikarn en-aut-sei=Seetasang en-aut-mei=Sasikarn kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=KanetaTakashi en-aut-sei=Kaneta en-aut-mei=Takashi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= affil-num=1 en-affil=Department of Chemistry, Graduate School of Natural Science and Technology, Okayama University kn-affil= affil-num=2 en-affil=Department of Chemistry, Graduate School of Natural Science and Technology, Okayama University kn-affil= en-keyword=Light-emitting diode kn-keyword=Light-emitting diode en-keyword=Paraquat kn-keyword=Paraquat en-keyword=Portable photometric detector kn-keyword=Portable photometric detector en-keyword=Rice field kn-keyword=Rice field en-keyword=Sodium dithionite kn-keyword=Sodium dithionite en-keyword=Thailand kn-keyword=Thailand END start-ver=1.4 cd-journal=joma no-vol=1625 cd-vols= no-issue= article-no= start-page=461513 end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2020 dt-pub=20200829 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Indirect capillary electrophoresis immunoassay of membrane protein in extracellular vesicles en-subtitle= kn-subtitle= en-abstract= kn-abstract=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. en-copyright= kn-copyright= en-aut-name=TaniYumeki en-aut-sei=Tani en-aut-mei=Yumeki kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=KanetaTakashi en-aut-sei=Kaneta en-aut-mei=Takashi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= affil-num=1 en-affil=Department of Chemistry, Graduate School of Natural Science and Technology, Okayama University kn-affil= affil-num=2 en-affil=Department of Chemistry, Graduate School of Natural Science and Technology, Okayama University kn-affil= en-keyword=Capillary electrophoresis immunoassay kn-keyword=Capillary electrophoresis immunoassay en-keyword=Laser-induced fluorescence kn-keyword=Laser-induced fluorescence en-keyword=Membrane protein kn-keyword=Membrane protein en-keyword=CD63 kn-keyword=CD63 en-keyword=Extracellular vesicle kn-keyword=Extracellular vesicle END start-ver=1.4 cd-journal=joma no-vol=9 cd-vols= no-issue= article-no= start-page=12951 end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2019 dt-pub=2019910 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title= Long-term stabilization of hydrogen peroxide by poly(vinyl alcohol) on paper-based analytical devices en-subtitle= kn-subtitle= en-abstract= kn-abstract= 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. en-copyright= kn-copyright= en-aut-name=BoonpoempoonTuchpongpuch en-aut-sei=Boonpoempoon en-aut-mei=Tuchpongpuch kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=WonsawatWanida en-aut-sei=Wonsawat en-aut-mei=Wanida kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=KanetaTakashi en-aut-sei=Kaneta en-aut-mei=Takashi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= affil-num=1 en-affil=Department of Chemistry, Faculty of Science and Technology, Suan Sunandha Rajabhat University kn-affil= affil-num=2 en-affil=Department of Chemistry, Faculty of Science and Technology, Suan Sunandha Rajabhat University kn-affil= affil-num=3 en-affil=Department of Chemistry, Graduate School of Natural Science and Technology, Okayama University kn-affil= END start-ver=1.4 cd-journal=joma no-vol=54 cd-vols= no-issue=2 article-no= start-page=117 end-page=141 dt-received= dt-revised= dt-accepted= dt-pub-year=2018 dt-pub=20180419 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Microfluidic paper-based analytical devices with instrument-free detection and miniaturized portable detectors en-subtitle= kn-subtitle= en-abstract= kn-abstract= icrofluidic 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. en-copyright= kn-copyright= en-aut-name=KanetaTakashi en-aut-sei=Kaneta en-aut-mei=Takashi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=AlahmadWaleed en-aut-sei=Alahmad en-aut-mei=Waleed kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=VaranusupakulPakorn en-aut-sei=Varanusupakul en-aut-mei=Pakorn kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= affil-num=1 en-affil=Department of Chemistry, Graduate School of Natural Science and Technology, Okayama University kn-affil= affil-num=2 en-affil=Approaches for Food Applications Research Group, Faculty of Science, Chulalongkorn University kn-affil= affil-num=3 en-affil=Approaches for Food Applications Research Group, Faculty of Science, Chulalongkorn University kn-affil= en-keyword=Microfluidic paper-based analytical device kn-keyword=Microfluidic paper-based analytical device en-keyword=paper-based analytical device kn-keyword=paper-based analytical device en-keyword=point-of-care testing kn-keyword=point-of-care testing en-keyword=onsite analysis kn-keyword=onsite analysis END start-ver=1.4 cd-journal=joma no-vol=6 cd-vols= no-issue=5 article-no= start-page=190293 end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2019 dt-pub=20190515 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Enhancement of optical force acting on vesicles via the binding of gold nanoparticles en-subtitle= kn-subtitle= en-abstract= kn-abstract= 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. en-copyright= kn-copyright= en-aut-name=TaniYumeki en-aut-sei=Tani en-aut-mei=Yumeki kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=KanetaTakashi en-aut-sei=Kaneta en-aut-mei=Takashi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= affil-num=1 en-affil=Department of Chemistry, Graduate School of Natural Science and Technology, Okayama University kn-affil= affil-num=2 en-affil=Department of Chemistry, Graduate School of Natural Science and Technology, Okayama University kn-affil= en-keyword=gold nanoparticle kn-keyword=gold nanoparticle en-keyword=optical force kn-keyword=optical force en-keyword=vesicles kn-keyword=vesicles END start-ver=1.4 cd-journal=joma no-vol=11 cd-vols= no-issue= article-no= start-page=179 end-page=184 dt-received= dt-revised= dt-accepted= dt-pub-year=2018 dt-pub=20181210 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Chromatographic paper-based analytical devices using an oxidized paper substrate en-subtitle= kn-subtitle= en-abstract= kn-abstract= 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, Rf, 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. en-copyright= kn-copyright= en-aut-name=HashimotoYuki en-aut-sei=Hashimoto en-aut-mei=Yuki kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=KanetaTakashi en-aut-sei=Kaneta en-aut-mei=Takashi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= affil-num=1 en-affil=Department of Chemistry, Graduate School of Natural Science and Technology, Okayama University kn-affil= affil-num=2 en-affil=Department of Chemistry, Graduate School of Natural Science and Technology, Okayama University kn-affil= END start-ver=1.4 cd-journal=joma no-vol=19 cd-vols= no-issue=2-3 article-no= start-page=452 end-page=461 dt-received= dt-revised= dt-accepted= dt-pub-year=2018 dt-pub=20180806 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Laser-Induced Fluorometry for Capillary Electrophoresis en-subtitle= kn-subtitle= en-abstract= kn-abstract= 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. en-copyright= kn-copyright= en-aut-name=KanetaTakashi en-aut-sei=Kaneta en-aut-mei=Takashi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= affil-num=1 en-affil=Department of Chemistry, Graduate School of Natural Science and Technology, Okayama University kn-affil= en-keyword=DNA sequencing kn-keyword=DNA sequencing en-keyword=capillary electrophoresis kn-keyword=capillary electrophoresis en-keyword=laser-induced fluorescence kn-keyword=laser-induced fluorescence en-keyword=micellar electrokinetic chromatography kn-keyword=micellar electrokinetic chromatography END start-ver=1.4 cd-journal=joma no-vol=4 cd-vols= no-issue=12 article-no= start-page=15249 end-page=15254 dt-received= dt-revised= dt-accepted= dt-pub-year=2019 dt-pub=20190703 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Characterization of Pieces of Paper That Form Reagent Containers for Use as Portable Analytical Devices en-subtitle= kn-subtitle= en-abstract= kn-abstract= 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. en-copyright= kn-copyright= en-aut-name=BukingSupatana en-aut-sei=Buking en-aut-mei=Supatana kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=SuedomiYusuke en-aut-sei=Suedomi en-aut-mei=Yusuke kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=NacaprichaDuangjai en-aut-sei=Nacapricha en-aut-mei=Duangjai kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=KanetaTakashi en-aut-sei=Kaneta en-aut-mei=Takashi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= affil-num=1 en-affil=Flow Innovation-Research for Science and Technology Laboratories (FIRST Labs) and Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Mahidol University kn-affil= affil-num=2 en-affil=Department of Chemistry, Graduate School of Natural Science and Technology, Okayama University kn-affil= affil-num=3 en-affil=Flow Innovation-Research for Science and Technology Laboratories (FIRST Labs) and Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Mahidol University kn-affil= affil-num=4 en-affil=Department of Chemistry, Graduate School of Natural Science and Technology, Okayama University kn-affil= END start-ver=1.4 cd-journal=joma no-vol=924 cd-vols= no-issue= article-no= start-page=60 end-page=67 dt-received= dt-revised= dt-accepted= dt-pub-year=2016 dt-pub=20160614 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Chelate titrations of Ca2+ and Mg2+ using microfluidic paper-based analytical devices en-subtitle= kn-subtitle= en-abstract= kn-abstract=We developed microfluidic paper-based analytical devices (μPADs) for the chelate titrations of Ca2+ and Mg2+ in natural water. The μPAD consisted of ten reaction zones and ten detection zones connected through narrow channels to a sample zone located at the center. Buffer solutions with a pH of 10 or 13 were applied to all surfaces of the channels and zones. Different amounts of ethylenediaminetetraacetic acid (EDTA) were added to the reaction zones and a consistent amount of a metal indicator (Eriochrome Black T or Calcon) was added to the detection zones. The total concentrations of Ca2+ and Mg2+ (total hardness) in the water were measured using a μPAD containing a buffer solution with a pH of 10, whereas only Ca2+ was titrated using a μPAD prepared with a potassium hydroxide solution with a pH of 13. The μPADs permitted the determination of Ca2+ and Mg2+ in mineral water, river water, and seawater samples within only a few minutes using only the naked eye—no need of instruments. en-copyright= kn-copyright= en-aut-name=KaritaShingo en-aut-sei=Karita en-aut-mei=Shingo kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=KanetaTakashi en-aut-sei=Kaneta en-aut-mei=Takashi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= affil-num=1 en-affil=Department of Chemistry, Graduate School of Natural Science and Technology, Okayama University kn-affil=岡山大学大学院自然科学研究科 affil-num=2 en-affil=Department of Chemistry, Graduate School of Natural Science and Technology, Okayama University kn-affil=岡山大学大学院自然科学研究科 en-keyword=Chelate titration kn-keyword=Chelate titration en-keyword=Microfluidic paper-based analytical device kn-keyword=Microfluidic paper-based analytical device en-keyword=Hardness kn-keyword=Hardness en-keyword=Calcium kn-keyword=Calcium en-keyword=Magnesium kn-keyword=Magnesium en-keyword=Natural water kn-keyword=Natural water END start-ver=1.4 cd-journal=joma no-vol=1440 cd-vols= no-issue= article-no= start-page=145 end-page=149 dt-received= dt-revised= dt-accepted= dt-pub-year=2016 dt-pub=20160401 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Direct determination of lignin peroxidase released from Phanerochaete chrysosporium by in-capillary enzyme assay using micellar electrokinetic chromatography en-subtitle= kn-subtitle= en-abstract= kn-abstract=Here we describe the application of an in-capillary enzyme assay using micellar electrokinetic chromatography (MEKC) in the determination of enzyme activity in a crude culture medium containing lignin peroxidase released from Phanerochaete chrysosporium (P. chrysosporium). The method consists of a plug–plug reaction between lignin peroxidase and its substrate, veratryl alcohol, the separation of the product, veratraldehyde, from the other components including the enzyme and the culture medium, and the determination of the enzyme activity from the peak area of veratraldehyde produced by the plug–plug reaction. This method is more sensitive than conventional spectrophotometry since the background originates from the enzyme and the culture medium can be removed via MEKC separation. Veratraldehyde was separated at −10 kV in a background electrolyte containing 50 mM tartrate buffer (pH 2.5) and 50 mM sodium dodecyl sulfate (SDS) after a plug–plug reaction in the capillary for 5 min. The calibration curve of veratraldehyde was linear up to 4 pmol (500 μM) with a limit to quantification of 0.026 pmol (3.2 μM) (SN = 10). The activity of lignin peroxidase was directly measured from the peak area of veratraldehyde. The activity of lignin peroxidase released from P. chrysosporium into the medium for 7 days was successfully determined to be 3.40 UL−1. en-copyright= kn-copyright= en-aut-name=HaradaAiri en-aut-sei=Harada en-aut-mei=Airi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=SasakiKeiko en-aut-sei=Sasaki en-aut-mei=Keiko kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=KanetaTakashi en-aut-sei=Kaneta en-aut-mei=Takashi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= affil-num=1 en-affil= kn-affil=Department of Chemistry, Graduate School of Natural Science and Technology, Okayama University affil-num=2 en-affil= kn-affil=Department of Earth Resources Engineering, Graduate School of Engineering, Kyushu University affil-num=3 en-affil= kn-affil=Department of Chemistry, Graduate School of Natural Science and Technology, Okayama University en-keyword=Lignin Peroxidase kn-keyword=Lignin Peroxidase en-keyword=Phanerochaete chrysosporium kn-keyword=Phanerochaete chrysosporium en-keyword=Micellar electrokinetic chromatography kn-keyword=Micellar electrokinetic chromatography en-keyword=Capillary electrophoresis kn-keyword=Capillary electrophoresis en-keyword=Enzyme assay kn-keyword=Enzyme assay END start-ver=1.4 cd-journal=joma no-vol=122 cd-vols= no-issue= article-no= start-page=240 end-page=245 dt-received= dt-revised= dt-accepted= dt-pub-year=2014 dt-pub=201405 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Speciation of arsenic in a thermoacidophilic iron-oxidizing archaeon, Acidianus brierleyi, and its culture medium by inductively coupled plasma–optical emission spectroscopy combined with flow injection pretreatment using an anion-exchange mini-column en-subtitle= kn-subtitle= en-abstract= kn-abstract=The thermoacidophilic iron-oxidizing archaeon Acidianus brierleyi is a microorganism that could be useful in the removal of inorganic As from wastewater, because it simultaneously oxidizes As(III) and Fe(II) to As(V) and Fe(III) in an acidic culture medium, resulting in the immobilization of As(V) as FeAsO4. To investigate the oxidation mechanism, speciation of the As species in both the cells and its culture media is an important issue. Here we describe the successive determination of As(III), As(V), and total As in A. brierleyi and its culture medium via a facile method based on inductively coupled plasma–optical emission spectroscopy (ICP–OES) with a flow injection pretreatment system using a mini-column packed with an anion-exchange resin. The flow-injection pretreatment system consisted of a syringe pump, a selection valve, and a switching valve, which were controlled by a personal computer. Sample solutions with the pH adjusted to 5 were flowed into the mini-column to retain the anionic As(V), whereas As(III) was introduced into ICP–OES with no adsorption on the mini-column due to its electrically neutral form. An acidic solution (1 M HNO3) was then flowed into the mini-column to elute As(V) followed by ICP–OES measurement. The same sample was also subjected to ICP–OES without being passed through the mini-column in order to determine the total amounts of As(III) and As(V). The method was verified by comparing the results of the total As with the sum of As(III) and As(V). The calibration curves showed good linearity with limits of detection of 158, 86, and 211 ppb for As(III), As(V), and total As, respectively. The method was successfully applicable to the determination of the As species contained in the pellets of A. brierleyi and their culture media. The results suggested that the oxidation of As(III) was influenced by the presence of Fe(II) in the culture medium, i.e., Fe(II) enhanced the oxidation of As(III) in A. brierleyi. In addition, we found that no soluble As species was contained in the cell pellets and more than 60% of the As(III) in the culture medium was oxidized by A. brierleyi after a 6-day incubation. en-copyright= kn-copyright= en-aut-name=HigashidaniNaoki en-aut-sei=Higashidani en-aut-mei=Naoki kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=KanetaTakashi en-aut-sei=Kaneta en-aut-mei=Takashi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=TakeyasuNobuyuki en-aut-sei=Takeyasu en-aut-mei=Nobuyuki kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=MotomizuShoji en-aut-sei=Motomizu en-aut-mei=Shoji kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= en-aut-name=OkibeNaoko en-aut-sei=Okibe en-aut-mei=Naoko kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=5 ORCID= en-aut-name=SasakiKeiko en-aut-sei=Sasaki en-aut-mei=Keiko kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=6 ORCID= affil-num=1 en-affil= kn-affil=Department of Chemistry, Graduate School of Natural Science and Technology, Okayama University affil-num=2 en-affil= kn-affil=Department of Chemistry, Graduate School of Natural Science and Technology, Okayama University affil-num=3 en-affil= kn-affil=Department of Chemistry, Graduate School of Natural Science and Technology, Okayama University affil-num=4 en-affil= kn-affil=Okayama University affil-num=5 en-affil= kn-affil=Department of Earth Resources Engineering, Graduate School of Engineering, Kyushu University affil-num=6 en-affil= kn-affil=Department of Earth Resources Engineering, Graduate School of Engineering, Kyushu University en-keyword=Thermoacidophilic iron-oxidizing archaeon kn-keyword=Thermoacidophilic iron-oxidizing archaeon en-keyword=Acidianus brierleyi kn-keyword=Acidianus brierleyi en-keyword=Arsenic kn-keyword=Arsenic en-keyword=Speciation kn-keyword=Speciation en-keyword=Inductively coupled plasma–optical emission spectroscopy kn-keyword=Inductively coupled plasma–optical emission spectroscopy en-keyword=Flow injection pretreatment kn-keyword=Flow injection pretreatment END start-ver=1.4 cd-journal=joma no-vol=34 cd-vols= no-issue=16 article-no= start-page=2316 end-page=2322 dt-received= dt-revised= dt-accepted= dt-pub-year=2013 dt-pub=201308 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Discrimination of glycoproteins via two-color laser-induced fluorescence detection coupled with postcolumn derivatization in capillary electrophoresis en-subtitle= kn-subtitle= en-abstract= kn-abstract=Here, we report a novel method consisting of capillary electrophoretic separation followed by two-color LIF detection with postcolumn derivatization. The method can be used to discriminate glycoproteins in a protein mixture containing both glycosylated and unglycosylated proteins. The detector permitted simultaneous measurements of two electropherograms obtained by 450 nm (diode laser) and 532 nm (Nd:YAG laser) lasers excited native proteins following postcolumn derivatization with naphthalene-2,3-dicarboxaldehyde and concanavalin A (Con A) labeled with tetramethylrhodamine (rhodamine-labeled Con A), respectively. So, a protein can be assigned as glycosylated if it shows a peak at the same migration time in both electropherograms. According to the proposed principle, in a single run we discriminated a glycosylated protein (thyroglobulin) from an unglycosylated protein (albumin) in the presence of rhodamine-labeled Con A. Because the methodology permits the simultaneous detection of native proteins and their complexes with a fluorescently labeled probe, it should have broad applicability to binding assays. en-copyright= kn-copyright= en-aut-name=TabaraAyumi en-aut-sei=Tabara en-aut-mei=Ayumi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=KanetaTakashi en-aut-sei=Kaneta en-aut-mei=Takashi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= affil-num=1 en-affil= kn-affil=Department of Chemistry, Graduate School of Natural Science and Technology, Okayama University affil-num=2 en-affil= kn-affil=Department of Chemistry, Graduate School of Natural Science and Technology, Okayama University en-keyword=Capillary electrophoresis kn-keyword=Capillary electrophoresis en-keyword=Concanavalin A kn-keyword=Concanavalin A en-keyword=Glycoprotein kn-keyword=Glycoprotein en-keyword=Postcolumn derivatization kn-keyword=Postcolumn derivatization en-keyword=Two-color laser-induced fluorescence kn-keyword=Two-color laser-induced fluorescence END start-ver=1.4 cd-journal=joma no-vol=5 cd-vols= no-issue=11 article-no= start-page=2854 end-page=2859 dt-received= dt-revised= dt-accepted= dt-pub-year=2013 dt-pub=201305 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Determination of polyamines in Arabidopsis thaliana by capillary electrophoresis using salicylaldehyde-5-sulfonate as a derivatizing reagent en-subtitle= kn-subtitle= en-abstract= kn-abstract=Herein, we report a novel method for the determination of polyamines in a sample extracted from Arabidopsis thaliana by capillary electrophoresis (CE) using salicylaldehyde-5-sulfonate (SAS) as a derivatizing reagent. An aldehyde group of SAS forms a Schiff base with amino groups of aliphatic polyamines, resulting in an anionic species with an absorption band in the ultraviolet region. The derivatization method was straightforward since the derivatives were formed by mixing a sample with the derivatizing reagent at a neutral pH. In addition, the negative charges induced by SAS led to a high resolution with a short analysis time. This method permitted the separation of five polyamines, which play important roles in plants. However, further improvement in sensitivity was needed for the determination of the polyamines in plant samples. Therefore, the CE method was coupled with solid-phase extraction (SPE) using an ion-pairing formation with sodium dodecyl benzene sulfonate. The SPE method improved the concentration limits of detection to sub-μM levels, which corresponded with a 10-fold enhancement. The calibration curves for cadaverine, putrescine, and spermidine were linear with concentrations that ranged from 1 to 20 μM and correlation coefficients (R2) were greater than 0.998. The proposed method was applied to the determination of spermidine in a plant sample, Arabidopsis thaliana. en-copyright= kn-copyright= en-aut-name=InoueGenki en-aut-sei=Inoue en-aut-mei=Genki kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=KanetaTakashi en-aut-sei=Kaneta en-aut-mei=Takashi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=TakayanagiToshio en-aut-sei=Takayanagi en-aut-mei=Toshio kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=KakehiJunichi en-aut-sei=Kakehi en-aut-mei=Junichi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= en-aut-name=MotoseHiroyasu en-aut-sei=Motose en-aut-mei=Hiroyasu kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=5 ORCID= en-aut-name=TakahashiTaku en-aut-sei=Takahashi en-aut-mei=Taku kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=6 ORCID= affil-num=1 en-affil= kn-affil=Department of Chemistry, Division of Earth, Life, and Molecular Sciences, Graduate School of Natural Science and Technology, Okayama University affil-num=2 en-affil= kn-affil=Department of Chemistry, Division of Earth, Life, and Molecular Sciences, Graduate School of Natural Science and Technology, Okayama University affil-num=3 en-affil= kn-affil=Department of Life System, Institute of Technology and Science, The University of Tokushima affil-num=4 en-affil= kn-affil=Department of Biological Science, Division of Earth, Life, and Molecular Sciences, Graduate School of Natural Science and Technology, Okayama University affil-num=5 en-affil= kn-affil=Department of Biological Science, Division of Earth, Life, and Molecular Sciences, Graduate School of Natural Science and Technology, Okayama University affil-num=6 en-affil= kn-affil=Department of Biological Science, Division of Earth, Life, and Molecular Sciences, Graduate School of Natural Science and Technology, Okayama University END start-ver=1.4 cd-journal=joma no-vol=1288 cd-vols= no-issue= article-no= start-page=149 end-page=154 dt-received= dt-revised= dt-accepted= dt-pub-year=2013 dt-pub=20130503 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Determination of association constants between 5 '-guanosine monophosphate gel and aromatic compounds by capillary electrophoresis en-subtitle= kn-subtitle= en-abstract= kn-abstract=Hydro gel formed by 5'-guanosine monophosphate (GMP) in the presence of a potassium ion is expected to exhibit interesting selectivity in capillary electrophoretic separations. Here, we estimated the conditional association constants between the hydro gel (G-gel) and aromatic compounds by capillary electrophoresis in order to investigate the separation selectivity that is induced by the G-gel. Several aromatic compounds were separated in a solution containing GMP and potassium ion at different concentrations. The association constants were calculated by correlating the electrophoretic mobilities of the analytes obtained experimentally using a concentration of G-gel. During semi-quantitative estimation, naphthalene derivatives had larger association constants (K-ass = 10.3-16.8) compared with those of benzene derivatives (K-ass = 3.91-5.31), which means that the binding sites of G-gel match better to a naphthalene ring than to a benzene ring. A hydrophobic interaction was also found when the association constants for alkyl resorcinol were compared with those of different hydrocarbon chains. The association constants of nucleobases and tryptophan ranged from 6.05 to 12.6, which approximated the intermediate values between benzene and naphthalene derivatives. Consequently, the selective interaction between G-gel and aromatic compounds was classified as one of three types: (1) an intercalation into stacked planar GMP tetramers; (2) a hydrophobic interaction with a long alkyl chain; or, (3) a small contribution of steric hindrance and/or hydrogen bonding with functional groups such as amino and hydroxyl groups. en-copyright= kn-copyright= en-aut-name=YamaguchiKaori en-aut-sei=Yamaguchi en-aut-mei=Kaori kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=TakeyasuNobuyuki en-aut-sei=Takeyasu en-aut-mei=Nobuyuki kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=KanetaTakashi en-aut-sei=Kaneta en-aut-mei=Takashi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= affil-num=1 en-affil= kn-affil=Okayama Univ, Grad Sch Nat Sci & Technol, Div Earth Life & Mol Sci, Dept Chem affil-num=2 en-affil= kn-affil=Okayama Univ, Grad Sch Nat Sci & Technol, Div Earth Life & Mol Sci, Dept Chem affil-num=3 en-affil= kn-affil=Okayama Univ, Grad Sch Nat Sci & Technol, Div Earth Life & Mol Sci, Dept Chem en-keyword=Capillary electrophoresis kn-keyword=Capillary electrophoresis en-keyword=5 '-Guanosine monophosphate (GMP) kn-keyword=5 '-Guanosine monophosphate (GMP) en-keyword=G-gel kn-keyword=G-gel en-keyword=Association constant kn-keyword=Association constant END