2003-2018, *Corresponding author

T. Hamamoto* and S. Katsuta*, An ionic liquid-based microextraction method for ultra-high preconcentration of paraquat traces in water samples prior to HPLC determination, Anal. Sci., in press. DOI: 10.2116/analsci.18P369

S. Katsuta* and J. Tamura, Extraction of palladium(II) and platinum(IV) from hydrochloric acid solutions with trioctylammonium nitrate ionic liquid without dilution, J. Solution Chem., 47 (8), 1293-1308 (2018). DOI: 10.1007/s10953-018-0745-9

S. Katsuta*, Y. Saito, and S. Takahashi, Application of a lithium-ion selective metallacrown to extraction–spectrophotometric determination of lithium in saline water, Anal. Sci., 34 (2), 189-193 (2018). DOI: 10.2116/analsci.34.189 selected as a Hot Article and Cover Illustration

S. Katsuta*, N. Kanaya, K. Bessho, and H. Monjushiro, Adsorption behavior of trace beryllium(II) onto metal oxide nanoparticles dispersed in water, Int. J. Chem., 9 (4), 62-70 (2017). DOI: 10.5539/ijc.v9n4p62

S. Katsuta* and T. Nakamura, Solid-phase extraction of lithium in seawater with porous polymer resin impregnated with lithium-ion selective metallohost, Bull. Soc. Sea Water Sci., Jpn., 71 (5), 298-299 (2017).

S. Katsuta*, Y. Watanabe, Y. Araki, and Y. Kudo, Extraction of gold(III) from hydrochloric acid into various ionic liquids: relationship between extraction efficiency and aqueous solubility of ionic liquids, ACS Sustainable Chem. Eng., 4 (2), 564-571 (2016). DOI: 10.1021/acssuschemeng.5b00976

Y. Kudo*, S. Katsuta, Y. Ohsawa, and K. Nozaki, Solvent extraction of cadmium picrate by 18-crown-6 ether into several less-polar diluents and nitrobenzene: re-evaluation of the corresponding overall extraction systems, J. Thermodyn. Catal., 6 (2), no.146 (2015).

K. Moriyama*, T. Sugiue, Y. Saito, S. Katsuta, and H. Togo*, 2,6-Bis(amido)benzoic acid with internal hydrogen bond as brønsted acid catalyst for Friedel–Crafts reaction of indoles, Adv. Synth. Catal., 357 (9), 2143-2149 (2015).

T. Hamamoto, M. Okai, and S. Katsuta*, The laws governing ionic liquid extraction of cations: partition of 1-ethylpyridinium monocation and paraquat dication in ionic liquid/water biphasic systems, J. Phys. Chem. B, 119 (20), 6317-6325 (2015). DOI: 10.1021/acs.jpcb.5b02923

Y. Kudo* and S. Katsuta, On an expression of extraction constants without the interfacial equilibrium-potential differences for the extraction of univalent and divalent metal picrates by crown ethers into 1,2-dichloroethane and nitrobenzene, Am. J. Anal. Chem., 6 (4), 350-363 (2015).

N. Kanaya, S. Matsuhashi, and S. Katsuta*, Extraction properties of p-methyloxacalix[3]arene methyl ether for alkali metal ions, Solv. Extr. Res. Dev. Jpn., 22 (1), 17-24 (2015). DOI: 10.15261/serdj.22.17

K. Bessho*, N. Kanaya, S. Shimada, S. Katsuta, and H. Monjushiro, Adsorption behavior of beryllium(II) on copper-oxide nanoparticles dispersed in water: A model for 7Be colloid formation in the cooling water for electromagnets at high-energy accelerator facilities, Anal. Sci., 30 (11), 1069-1074 (2014). DOI: 10.2116/analsci.30.1069

渡邉悠太, 荒木悠輔, 勝田正一*, プロトン性イオン液体による塩酸溶液からの金（Ⅲ）の抽出挙動, 分析化学, 63 (7), 563-567 (2014). DOI: 10.2116/bunsekikagaku.63.5637

Y. Kudo*, M. Ogihara, S. Katsuta, and Y. Takeda, An electrochemical understanding of extraction of silver picrate by benzo-​3m-​crown-​m ethers (m = 5, 6) into 1,​2-​dichloroethane and dichloromethane, Am. J. Anal. Chem., 5 (7), 433-444 (2014).

Y. Kudo*, Y. Takahashi, C. Numako, S. Katsuta, Extraction of lead picrate by 18-crown-6 ether into various diluents: Examples of sub-analysis of overall extraction equilibrium based on component equilibria, J. Mol. Liquids, 194, 121-129 (2014).

Y. Watanabe and S. Katsuta*, Distribution of a monovalent anion in various ionic liquid/water biphasic systems: relationship of the distribution ratio of picrate ions with the aqueous solubility of ionic liquids, J. Chem. Eng. Data, 59 (3), 696-701 (2014). DOI: 10.1021/je400726y

S. Katsuta*, H. Nomura, T. Egashira, N. Kanaya, and Y. Kudo, Highly lithium-ion selective ionophores: macrocyclic trinuclear complexes of methoxy-substituted arene ruthenium bridged by 2,3-pyridinediolate, New J. Chem., 37, 3634-3639 (2013). DOI: 10.1039/c3nj00761h

勝田正一, イオン液体/水二相系における中性及び陰イオン性化合物の分配挙動（総合論文）, 分析化学, 62 (4), 297-315 (2013). DOI: 10.2116/bunsekikagaku.62.297

Y. Kudo*, Y. Takahashi, and S. Katsuta, Distribution of picric acid into various diluents, Journal of Chemistry, 2013, Article ID 869506 (2013).

Y. Kudo*, N. Horiuchi, S. Katsuta, and Y. Takeda, Extraction of cadmium bromide and picrate by 18-crown-6 ether into various less-polar diluents: analysis of overall extraction equilibria based on their component equilibria with formation of their ion pairs in water, J. Mol. Liquids, 177, 257-266 (2013).

S. Katsuta*, M. Okai, Y. Yoshimoto, and Y. Kudo, Extraction of gallium(III) from hydrochloric acid solutions by trioctylammonium-based mixed ionic liquids, Anal. Sci., 28 (10), 1009-1012 (2012). DOI: 10.2116/analsci.28.1009

S. Katsuta*, Y. Shimizu, R. Takahashi, N. Kanaya, T. Imoto, and Y. Takeda, Metal complexes of tripodal ligands as ionophores for alkali metal ions, New J. Chem., 36 (7), 1445-1448 (2012). DOI: 10.1039/C2NJ40171A

S. Katsuta*, K. Nakamura, Y. Kudo, and Y. Takeda, Mechanisms and rules of anion partition into ionic liquids: phenolate ions in ionic liquid/water biphasic systems, J. Phys. Chem. B, 116 (2), 852-859 (2012). DOI: 10.1021/jp210444n

S. Shimada, K. Bessho*, S. Katsuta, H. Monjushiro, Y. Kudo, and Y. Takeda, Adsorption behavior of beryllium(II) on copper-oxide colloids in water, KEK Proceedings, 2012-6, 275-282 (2012).

Y. Kudo*, S. Katsuta, and Y. Takeda, Evaluation of overall extraction constants for the crown ether-complex ions of alkali and alkaline-earth metal with counter picrate ions from water into nitrobenzene based on their component equilibrium constants, J. Mol. Liquids, 173, 66-70 (2012).

S. Katsuta*, Y. Yoshimoto, M. Okai, Y. Takeda, and K. Bessho, Selective extraction of palladium and platinum from hydrochloric acid solutions by trioctylammonium-based mixed ionic liquids, Ind. Eng. Chem. Res., 50 (22), 12735-12740 (2011). DOI: 10.1021/ie201310v

S. Katsuta*, K. Nakamura, Y. Kudo, Y. Takeda, and H. Kato, Partition behavior of chlorophenols and nitrophenols between hydrophobic ionic liquids and water, J. Chem. Eng. Data, 56 (11), 4083-4089 (2011). DOI: 10.1021/je200506p

K. Nakamura, Y. Kudo, Y. Takeda, and S. Katsuta*, Partition of substituted benzenes between hydrophobic ionic liquids and water: evaluation of interactions between substituents and ionic liquids, J. Chem. Eng. Data, 56 (5), 2160-2167 (2011). DOI: 10.1021/je101215x

S. Katsuta*, H. Nomura, T. Egashira, T. Imoto, Y. Kudo, and Yasuyuki Takeda, Extraction ability and selectivity for lithium ion of macrocyclic trinuclear (alkylbenzene)ruthenium(II) complexes bridged by 2,3-pyridinediolato ligands, Bull. Chem. Soc. Jpn., 84 (3), 259-265 (2011). DOI: 10.1246/bcsj.20100282 BCSJ Selected Paper

Y. Kudo*, T. Koide, Y. Zhao, S. Katsuta, and Y. Takeda, Ion-pair formation between Cd(II), Na(I), and Ag(I) complex ions with 18-crown-6 ether derivatives and various pairing anions in water: an understanding of the ion-pair formation based on the HSAB principle, Anal. Sci., 27 (12), 1207-1211 (2011).

Y. Kudo*, K. Harashima, K. Hiyoshi, J. Takagi, S. Katsuta, and Y. Takeda, Extraction of some univalent salts into 1,2-dichloroethane and nitrobenzene: analysis of overall extraction equilibrium based on elucidating ion-pair formation and evaluation of standard potentials for ion transfers at the interfaces between their diluents and water, Anal. Sci., 27 (9), 913-919 (2011).

Y. Kudo*, D. Todoroki, N. Suzuki, N. Horiuchi, S. Katsuta, and Y. Takeda, Elucidation of abnormal potential responses of cation-selective electrodes with solid-state membranes to aqueous solutions of CuCl2 and CdI2, Am. J. Anal. Chem., 2 (1), 9-17 (2011).

Y. Kudo*, K. Harashima, S. Katsuta, and Y. Takeda, Solvent extraction of sodium permanganate by mono-benzo 3m-crown-m ethers (m = 5, 6) into 1,2-dichloroethane and nitrobenzene: a method which analyzes the extraction system with the polar diluents, Int. J. Chem., 3 (1), 99-107 (2011).

S. Katsuta*, Y. Shiozawa, K. Imai, Y. Kudo, and Y. Takeda, Stability of ion pairs of bis(trifluoromethanesulfonyl)amide-based ionic liquids in dichloromethane, J. Chem. Eng. Data, 55 (4), 1588-1593 (2010). DOI: 10.1021/je900694m

K. Bessho*, H. Matsumura, N. Kinoshita, K. Masumoto, H. Monjushiro, M. Taira, M. Sato, M. Sawabe, A. Komiya, Y. Oki, S. Shimada, S. Katsuta, Analysis of colloidal species formed in the cooling water of high-energy accelerator facilities, KEK Proceedings, 2010-8, 19-26 (2010).

Y. Kudo*, D. Todoroki, N. Horiuchi, S. Katsuta, and Y. Takeda, Ion-pair formation of sodium salts of several oxo anions and cadmium halides in water and the distribution of monovalent sulfate ion pairs in nitrobenzene, J. Chem. Eng. Data, 55 (7), 2463-2469 (2010).

Y. Kudo*, S. Katsuta, and Y. Takeda, Evaluation of the hydrophilic properties of crown ether-ion-pair complexes with alkali metal picrates by their distribution into less-polar diluents, Anal. Sci., 25 (4), 563-566 (2009).

Y. Kudo*, Y. Kobayashi, S. Katsuta, and Y. Takeda, Ion-pair formation of cadmium-18-crown-6 ethers complex ions with picrate and chloride ions in water and distribution of its picrate ion-pair complex into benzene, J. Mol. Liquids, 146 (1-2), 60-65 (2009).

S. Katsuta*, T. Imoto, Y. Kudo, and Y. Takeda, Selective extraction of lithium with a macrocyclic trinuclear complex of (1,3,5-trimethylbenzene)ruthenium(II) bridged by 2,3-dioxopyridine, Anal. Sci., 24 (10), 1215-1217 (2008). DOI: 10.2116/analsci.24.1215 Hot Article Award of Analytical Sciences

S. Katsuta*, N. Yamaguchi, R. Ogawa, Y. Kudo, and Y. Takeda, Distribution of 1-alkyl-3-methylimidazolium ions and their ion pairs between dichloromethane and water, Anal. Sci., 24 (10), 1261-1267 (2008). DOI: 10.2116/analsci.24.1261

S. Katsuta*, K. Imai, Y. Kudo, Y. Takeda, H. Seki, and M. Nakakoshi, Ion pair formation of alkylimidazolium ionic liquids in dichloromethane, J. Chem. Eng. Data, 53 (7), 1528-1532 (2008). DOI: 10.1021/je800152d

S. Katsuta*, Y. Iwabe, Y. Kato, Y. Kudo, and Y. Takeda, Extraction properties for alkali metal picrates of macrocyclic trinuclear (p-cymene)ruthenium(II) and (pentamethylcyclopentadienyl)rhodium(III) complexes, Inorg. Chim. Acta, 361 (1), 103-108 (2008). DOI: 10.1016/j.ica.2007.06.027

Y. Kudo*, R. Fujihara, T. Ohtake, S. Katsuta, and Y. Takeda, Evaluation of the hydrophilic property of sodium ion-pair complexes with 3m-crown-m ethers (m = 5, 6) and their benzo-derivatives by solvent extraction, Anal. Sci., 24 (8), 999-1003 (2008).

S. Katsuta*, H. Wakabayashi, M. Tamaru, Y. Kudo, and Y. Takeda, Tetraalkylammonium picrates in dichloromethane-water system: ion-pair formation and liquid-liquid distribution of free ions and ion pairs, J. Solution Chem., 36 (4), 531-547 (2007). DOI: 10.1007/s10953-007-9121-x

S. Katsuta*, R. Ogawa, N. Yamaguchi, T. Ishitani, and Y. Takeda, Ion-pair formation of 1-alkyl-3-methylimidazolium salts in water, J. Chem. Eng. Data, 52 (1), 248-251 (2007). DOI: 10.1021/je060369p

Y. Takeda*, K. Endo, D. Yoshiyama, K. Watanabe, N. Fukada, and S. Katsuta, Quantitative elucidation of macrocyclic effect on extraction-ability and -selectivity. Benzo-18-crown-6 and its open-ring analog 1,2-bis[2-(2-methoxyethoxy)ethoxy]benzene-alkali metal picarte systems, J. Mol. Liquids, 130 (1-3), 21-28 (2007).

Y. Kudo*, R. Fujihara, S. Katsuta, and Y. Takeda, Hydration effect on the ion-pair extraction of lithium picrate by hydrophobic benzo-15-crown-5 ether into various less-polar diluents, Anal. Sci., 23 (8), 1003-1006 (2007).

Y. Kudo*, S. Takeuchi, Y. Kobayashi, S. Katsuta, and Y. Takeda, Potentiometric determination of ion-pair formation constants for cadmium, calcium salts, and cadmium-18-crown-6 ether derivative complexes with a sulfate ion in water, J. Chem. Eng. Data, 52 (5), 1747-1752 (2007).

Y. Kudo*, R. Fujihara, S. Katsuta, and Y. Takeda, Solvent extraction of sodium perrhenate by 3m-crown-m ethers (m = 5, 6) and their mono-benzo-derivatives into 1,2-dichloroethane: elucidation of an overall extraction equilibrium based on component equilibria containing an ion-pair formation in water, Talanta, 71 (2), 656-661 (2007).

Y. Kudo*, R. Fujihara, T. Ohtake, M. Wakasa, S. Katsuta, and Y. Takeda, Ion-pair formation of 3m-crown-m ether (m = 5, 6) and its monobenzo derivative complex ions with several pairing anions in water, J. Chem. Eng. Data, 51 (2), 604-608 (2006).

Y. Kudo*, J. Usami, S. Katsuta, and Y. Takeda, On the difference between ion-pair formation constants of crown ether-complex ions with picrate ion in water determined by solvent extraction and by potentiometry, J. Mol. Liquids, 123 (1), 29-37 (2006).

S. Katsuta*, T. Kuwano, Y. Ito, and Y. Takeda, Stability and solvation of 1:1 complexes of dibenzo-21-crown-7 with alkali metal ions in polar solvents, J. Chem. Eng. Data, 50 (4), 1313-1318 (2005). DOI: 10.1021/je050045l

S. Katsuta*, Y. Ito, Y. Kudo, and Y. Takeda, Stability and solvation of alkali metal ion complexes with dibenzo-30-crown-10, Inorg. Chim. Acta, 358 (3), 713-719 (2005). DOI: 10.1016/j.ica.2004.09.034

Y. Takeda*, M. Tanaka, S. Katsuta, and N. Fukada, Stabilities and transfer activity coefficients from water to polar nonaqueous solvents of 1,2-bis[2-(2-methoxyethoxy)ethoxy]benzene- and benzo-18-crown-6-cation complexes, J. Coord. Chem., 58 (4), 373-379 (2005).

Y. Kudo*, M. Wakasa, T. Ito, J. Usami, S. Katsuta, and Y. Takeda, Determination of the ion-pair formation constants of univalent metal-crown complex ions with anions in water using ion-selective electrodes: application of modified determination methods to several salts, Anal. Bioanal. Chem., 381 (2), 456-463 (2005).

S. Katsuta*, T. Ishitani, M. Suzuki, Y. Ishii, Y. Kudo, and Y. Takeda, Equilibrium studies on ion-pair formation in water and distribution between water and m-xylene of tetraalkylammonium picrates, J. Solution Chem., 33 (5), 437-451 (2004). DOI: 10.1023/B:JOSL.0000037769.56435.9c

S. Katsuta*, Y. Ito, and Y. Takeda, Stabilities in nitromethane of alkali metal ion complexes with dibenzo-18-crown-6 and dibenzo-24-crown-8 and their transfer from nitromethane to other polar solvents, Inorg. Chim. Acta, 357 (2), 541-547 (2004). DOI: 10.1016/j.ica.2003.08.011

Y. Takeda*, R. Taguchi, and S. Katsuta, Study on solute-solvent and solute-solute interactions for the dibenzo-24-crown-8-alkali metal picrate extraction system, J. Mol. Liquids, 115 (2-3), 139-147 (2004).

Y. Takeda*, A. Yasui, and S. Katsuta, Extraction of sodium and potassium perchlorates with dibenzo-18-crown-6 into various organic solvents.  Quantitative elucidation of anion effects on the extraction-ability and -selectivity, J. Incl. Phenom., 50 (3-4), 157-164 (2004).

Y. Kudo*, J. Usami , S. Katsuta, and Y. Takeda, Solvent extraction of silver picrate by 3m-crown-m ethers (m = 5, 6) and its mono-benzo-derivative from water into benzene or chloroform: elucidation of an extraction equilibrium using component equilibrium constants, Talanta, 62 (4), 701-706 (2004).

勝田正一*, 武田裕行, クラウンエーテル及びそのアルカリ金属イオン錯体の水－極性非水溶間移行活量係数（総合論文）, 分析化学, 52 (2), 89-105 (2003). DOI: 10.2116/bunsekikagaku.52.89

Y. Takeda*, T. Watanabe, H. Yamada, and S. Katsuta, Thermodynamic study on transfer between polar solvents of 15-crown-5, benzo-15-crown-5, and their 1:1 complexes with alkali metal ions, J. Mol. Liquids, 108 (1-3), 151-173 (2003).

Y. Kudo*, J. Usami, S. Katsuta, and Y. Takeda, Solvent extraction of permanganates (Na, K) by 18-crown-6 ether from water into 1,2-dichloroethane: elucidation of an extraction equilibrium based on component equilibria, Talanta, 59 (6), 1213-1218 (2003).

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