{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,18]],"date-time":"2026-08-18T04:58:15Z","timestamp":1787029095294,"version":"build-2736575974"},"reference-count":38,"publisher":"MDPI AG","issue":"22","license":[{"start":{"date-parts":[[2023,11,10]],"date-time":"2023-11-10T00:00:00Z","timestamp":1699574400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100000646","name":"Japan Society for the Promotion of Science (JSPS) KAKENHI","doi-asserted-by":"publisher","award":["19K05561"],"award-info":[{"award-number":["19K05561"]}],"id":[{"id":"10.13039\/501100000646","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100000646","name":"Japan Society for the Promotion of Science (JSPS) KAKENHI","doi-asserted-by":"publisher","award":["15K00579"],"award-info":[{"award-number":["15K00579"]}],"id":[{"id":"10.13039\/501100000646","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Molecules"],"abstract":"<jats:p>The design of a simple approach enabling the detection of bisphenol A (BPA) in water samples without the need for large amounts of solvents is of utmost importance. This paper reports a simple method for the separation, concentration, and quantification of BPA in water samples using high-performance liquid chromatography with fluorescence detection (HPLC-FLD) after its microextraction into an in situ formed organic ion-associate (IA) liquid phase (LP). Novel IA phase components without conjugated double bonds, such as benzene rings, were investigated. Ethylhexyloxypropylamine hydrochloride and sodium dodecyl sulfate solutions were added to the water samples to form IAs. The aqueous phase and ion-associate liquid phase (IALP) were separated by centrifugation. The aqueous phase was removed, and the liquid phase was recovered and measured using HPLC-FLD or HPLC-electrochemical detection (ECD). The concentrated phase (IALP) had a relatively low viscosity and could be injected directly into the chromatograph without dissolving it in organic solvents. The detection limits for BPA by HPLC-FLD and HPLC-ECD were 0.009 and 0.3 \u00b5g L\u22121, respectively.<\/jats:p>","DOI":"10.3390\/molecules28227525","type":"journal-article","created":{"date-parts":[[2023,11,13]],"date-time":"2023-11-13T02:46:47Z","timestamp":1699843607000},"page":"7525","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":5,"title":["In Situ Formation of a Relatively Transparent Ion-Associate Liquid Phase from an Aqueous Phase and Its Application to Microextraction\/High-Performance Liquid Chromatography\u2013Fluorescence Detection of Bisphenol A in Water"],"prefix":"10.3390","volume":"28","author":[{"given":"Noriko","family":"Hata","sequence":"first","affiliation":[{"name":"Major of Earth, Life and Environmental Science, Graduate School of Science and Engineering, University of Toyama, 3190 Gofuku, Toyama 930-8555, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Seira","family":"Takahashi","sequence":"additional","affiliation":[{"name":"Major of Earth, Life and Environmental Science, Graduate School of Science and Engineering, University of Toyama, 3190 Gofuku, Toyama 930-8555, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Sachiko","family":"Osada","sequence":"additional","affiliation":[{"name":"Major of Earth, Life and Environmental Science, Graduate School of Science and Engineering, University of Toyama, 3190 Gofuku, Toyama 930-8555, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Sakura","family":"Katagiri","sequence":"additional","affiliation":[{"name":"Major of Earth, Life and Environmental Science, Graduate School of Science and Engineering, University of Toyama, 3190 Gofuku, Toyama 930-8555, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Mayumi","family":"Naruse","sequence":"additional","affiliation":[{"name":"Major of Earth, Life and Environmental Science, Graduate School of Science and Engineering, University of Toyama, 3190 Gofuku, Toyama 930-8555, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Akane","family":"Igarashi","sequence":"additional","affiliation":[{"name":"Major of Earth, Life and Environmental Science, Graduate School of Science and Engineering, University of Toyama, 3190 Gofuku, Toyama 930-8555, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Kazuto","family":"Sazawa","sequence":"additional","affiliation":[{"name":"Major of Earth, Life and Environmental Science, Graduate School of Science and Engineering, University of Toyama, 3190 Gofuku, Toyama 930-8555, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Shigeru","family":"Taguchi","sequence":"additional","affiliation":[{"name":"Major of Earth, Life and Environmental Science, Graduate School of Science and Engineering, University of Toyama, 3190 Gofuku, Toyama 930-8555, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9102-3667","authenticated-orcid":false,"given":"Hideki","family":"Kuramitz","sequence":"additional","affiliation":[{"name":"Major of Earth, Life and Environmental Science, Graduate School of Science and Engineering, University of Toyama, 3190 Gofuku, Toyama 930-8555, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2023,11,10]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"e00175","DOI":"10.1016\/j.teac.2022.e00175","article-title":"Advances in on-site analytical sample preparation for analysis of environmental waters: A review","volume":"36","author":"Sajid","year":"2022","journal-title":"TrEAC Trends Env. Anal. Chem."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1007\/s44211-022-00215-2","article-title":"Water quality monitoring","volume":"39","author":"Tazoe","year":"2023","journal-title":"Anal. Sci."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"2502","DOI":"10.1002\/elps.201500519","article-title":"Dispersive liquid-liquid microextraction for four phenolic environmental estrogens in water samples followed by determination using capillary electrophoresis","volume":"37","author":"Liu","year":"2016","journal-title":"Electrophoresis"},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"2794","DOI":"10.1039\/C4AY03021D","article-title":"Visual colorimetry for determination of trace arsenic in groundwater based on improved molybdenum blue spectrophotometry","volume":"7","author":"Okazaki","year":"2015","journal-title":"Anal. Methods"},{"key":"ref_5","unstructured":"Ministry of the Environment, Japan (2023, June 23). Environmental Quality Standards for Water Pollution. Available online: https:\/\/www.env.go.jp\/en\/water\/wq\/wp.pdf."},{"key":"ref_6","unstructured":"WHO (2022). Guidelines for Drinking-Water Quality, World Health Organization. [4th ed.]. Incorporating the 1st and 2nd addenda."},{"key":"ref_7","unstructured":"Ministry of the Environment, Japan (2023, June 23). National Effluent Standards. Available online: https:\/\/www.env.go.jp\/en\/water\/wq\/nes.html."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"2745","DOI":"10.1002\/jssc.201400577","article-title":"Rapid pretreatment and determination of bisphenol A in water samples based on vortex-assisted liquid\u2013liquid microextraction followed by high-performance liquid chromatography with fluorescence detection","volume":"37","author":"Yang","year":"2014","journal-title":"J. Sep. Sci."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"461087","DOI":"10.1016\/j.chroma.2020.461087","article-title":"Hydrophobic deep eutectic solvents as extractants for the determination of bisphenols from food-contacted plastics by high performance liquid chromatography with fluorescence detection","volume":"1621","author":"Li","year":"2020","journal-title":"J. Chromatogr. A"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"107790","DOI":"10.1016\/j.microc.2022.107790","article-title":"Hydrophobic deep eutectic solvent based dispersive liquid\u2013liquid microextraction for the preconcentration and HPLC analysis of five rice paddy herbicides in water samples","volume":"181","author":"Wang","year":"2022","journal-title":"Microchem. J."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"108807","DOI":"10.1016\/j.microc.2023.108807","article-title":"Recent advances in dispersion strategies for dispersive liquid\u2013liquid microextraction from green chemistry perspectives","volume":"191","author":"Elmansi","year":"2023","journal-title":"Microchem. J."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"420","DOI":"10.1246\/cl.230058","article-title":"Simple and High-sensitivity Analysis of Small Microplastics with Phase Separation by Using Water\/isopropanol\/chloroform","volume":"52","author":"Manaka","year":"2023","journal-title":"Chem. Lett."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"229","DOI":"10.1016\/S0021-9673(97)00345-2","article-title":"Micelle-mediated extraction","volume":"780","author":"Tani","year":"1997","journal-title":"J. Chromatogr. A"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"3285","DOI":"10.1039\/C3AY42191K","article-title":"Cloud point extraction for the determination of bisphenol A, bisphenol AF and tetrabromobisphenol A in river water samples by high-performance liquid chromatography","volume":"6","author":"Li","year":"2014","journal-title":"Anal. Methods"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"1765","DOI":"10.1007\/s12161-016-0737-6","article-title":"A new ultrasonic thermostatic-assisted cloud point extraction\/spectrophotometric method for the preconcentration and determination of bisphenol A in food, milk, and water samples in contact with plastic products","volume":"10","author":"Altunay","year":"2017","journal-title":"Food Anal. Methods"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"105725","DOI":"10.1016\/j.jfca.2023.105725","article-title":"Application of chemometric modeling for ionic liquid-based ultrasonic-assisted dispersive liquid-liquid microextraction: Analysis of fosetyl-aluminum in fruit and vegetable samples","volume":"124","author":"Haq","year":"2023","journal-title":"J. Food Compos. Anal."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"460730","DOI":"10.1016\/j.chroma.2019.460730","article-title":"In situ formation of thymol-based hydrophobic deep eutectic solvents: Application to antibiotics analysis in surface water based on liquid-liquid microextraction followed by liquid chromatography","volume":"1614","author":"Li","year":"2020","journal-title":"J. Chromatogr. A"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"121527","DOI":"10.1016\/j.talanta.2020.121527","article-title":"Application of an in-situ formulated magnetic deep eutectic solvent for the determination of triazine herbicides in rice","volume":"222","author":"Piao","year":"2021","journal-title":"Talanta"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"697","DOI":"10.2116\/analsci.18.697","article-title":"Micro-phase sorbent extraction for trace analysis via in situ sorbent formation: Application to the preconcentration and the spectrophotometric determination of trace ammonia","volume":"18","author":"Hata","year":"2002","journal-title":"Anal. Sci."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"149","DOI":"10.2116\/analsci.20.149","article-title":"Micro-organic ion-associate phase extraction via in situ fresh phase formation for the preconcentration and determination of di(2-ethylhexyl)phthalate in river water by HPLC","volume":"20","author":"Hata","year":"2004","journal-title":"Anal. Sci."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"925","DOI":"10.2116\/analsci.24.925","article-title":"Formation of a liquid organic ion associate in aqueous solution and its application to the GF-AAS determination of trace cadmium in environmental water as a complex with 2-(5-bromo-2-pyridylazo)5-(N-propyl-N-sulfopropylamino)phenol","volume":"24","author":"Hata","year":"2008","journal-title":"Anal. Sci."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"595","DOI":"10.2116\/analsci.20SBP13","article-title":"Organic Ion-associate Phase Extraction\/Back-microextraction for the Preconcentration and Determination of Lithium Using 2,2,6,6-Tetramethyl-3,5-heptanedione by Liquid Electrode Plasma Atomic Emission Spectrometry and GF-AAS in Environmental Water","volume":"36","author":"Mizuna","year":"2020","journal-title":"Anal. Sci."},{"key":"ref_23","first-page":"130","article-title":"Organic Ion-Associate Phase Microextraction\/Back-Microextraction for Preconcentration: Determination of Nickel in Environmental Water Using 2-Thenoyltrifluoroacetone via GF-AAS","volume":"1","author":"Kosugi","year":"2021","journal-title":"Appl. Chem."},{"key":"ref_24","first-page":"32","article-title":"Evaluation of an Ion-Associate Phase Formed In Situ from the Aqueous Phase by Adding Benzethonium Chloride and Sodium Ethylbenzenesulfonate for Microextraction","volume":"3","author":"Hata","year":"2023","journal-title":"Appl. Chem."},{"key":"ref_25","unstructured":"Ministry of Economy, Trade and Industry (METI), Japan (2023, August 31). Yearbook of Current Production Statistics 2019: Chemical Industry. Available online: https:\/\/www.meti.go.jp\/statistics\/tyo\/seidou\/result\/gaiyo\/resourceData\/02_kagaku\/nenpo\/h2dbb2019k.pdf."},{"key":"ref_26","unstructured":"European Chemicals Agency (ECHA) (2023, August 31). All News: Four New Substances of Very High Concern Added to the Candidate List. Available online: https:\/\/echa.europa.eu\/-\/four-new-substances-of-very-high-concern-added-to-the-candidate-list."},{"key":"ref_27","unstructured":"Ministry of the Environment, Japan (2023, August 31). Environmental Risk Assessment of Chemical Substances, 15. Bisphenol A 2004, 20 Pages. Available online: https:\/\/www.env.go.jp\/chemi\/report\/h16-01\/pdf\/chap01\/02_2_15.pdf."},{"key":"ref_28","unstructured":"Ministry of Health, Labour and Welfare, Japan (2023, September 08). Drinking Water Quality Standards, Water Quality Control Target Setting Items (Pollutants). Available online: https:\/\/www.mhlw.go.jp\/stf\/seisakunitsuite\/bunya\/topics\/bukyoku\/kenkou\/suido\/kijun\/kijunchi.html#01."},{"key":"ref_29","unstructured":"(2023, September 12). Water Quality Management Division, Water Quality Protection Bureau, Environment Agency, Tentative Manual for Investigation of Exogenous Endocrine Disrupting Chemicals (Water Quality, Sediment, Aquatic Life), 1998. Available online: https:\/\/www.env.go.jp\/chemi\/end\/sympo\/manual199810\/water.html."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"45","DOI":"10.1002\/ieam.4611","article-title":"An overview of the occurrence, fate, and human risks of the bisphenol-A present in plastic materials, components, and products","volume":"19","author":"Hahladakis","year":"2023","journal-title":"Integr. Environ. Assess Manag."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"137763","DOI":"10.1016\/j.chemosphere.2023.137763","article-title":"Bisphenol A and its substitutes in the aquatic environment: Occurrence and toxicity assessment","volume":"315","author":"Krawczyk","year":"2023","journal-title":"Chemosphere"},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"3871","DOI":"10.1007\/s00216-018-1062-2","article-title":"Rapid and sensitive determination of nine bisphenol analogues, three amphenicol antibiotics, and six phthalate metabolites in human urine samples using UHPLC-MS\/MS","volume":"410","author":"Yao","year":"2018","journal-title":"Anal. Bioanal. Chem."},{"key":"ref_33","unstructured":"Ministry of Health, Labour and Welfare, Japan (2023, September 12). Safety Data Sheet. Dichloromethane. Available online: https:\/\/anzeninfo.mhlw.go.jp\/anzen\/gmsds\/75-09-2.html."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"894","DOI":"10.1246\/nikkashi.1986.894","article-title":"Assignment of Individual Ion-Pair Extraction Constants Based on the KPh4As+ = KPb4B-; Kbenzene = 1 Assumption","volume":"1986","author":"Kasahara","year":"1986","journal-title":"Nippon Kagaku Kaishi"},{"key":"ref_35","unstructured":"United States Environmental Protection Agency (US EPA, Washington, DC, USA) (2023, September 08). KOWWIN 1.68 in \u201cEstimation Programs Interface Suite\u2122 for Microsoft\u00ae Windows, v 4.11.\u201d 2012, Available online: https:\/\/www.epa.gov\/tsca-screening-tools\/epi-suitetm-estimation-program-interface."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"10585","DOI":"10.1016\/j.jfca.2022.105085","article-title":"Automated primary amine-based supramolecular solvent microextraction with monoterpenoid as coacervation agent before high-performance liquid chromatography","volume":"116","author":"Zhavoronok","year":"2023","journal-title":"J. Food Compos. Anal."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"101","DOI":"10.1007\/BF01242704","article-title":"Spectrophotometric Determination of Ammonia-Nitrogen After Preconcentration as Indothymol on a Glass-Fiber Filter in the Presence of a Cationic Surfactant","volume":"106","author":"Hata","year":"1992","journal-title":"Mikrochim. Acta"},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"201","DOI":"10.1007\/s00339-023-06482-8","article-title":"Micellization thermodynamics as a function of the temperature of a cationic zwitterionic dodecyl phosphocholine and anionic sodium dodecyl sulfate mixed micelles with fluorometry","volume":"129","author":"Gabal","year":"2023","journal-title":"Appl. Phys. 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