{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,22]],"date-time":"2026-09-22T09:01:48Z","timestamp":1790067708497,"version":"4.0.1"},"reference-count":68,"publisher":"MDPI AG","issue":"19","license":[{"start":{"date-parts":[[2026,9,22]],"date-time":"2026-09-22T00:00:00Z","timestamp":1790035200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"MES of the Republic of Bulgaria","award":["D01-98\/26.06.2025"],"award-info":[{"award-number":["D01-98\/26.06.2025"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Molecules"],"abstract":"<jats:p>The ability of 3,5-dinitrocatechol (3,5-DNC) to form anionic species with vanadium(V) in a mildly acidic medium was exploited to develop a spectrophotometric method for vanadium determination. The method is grounded on the formation of an ion-association complex with benzalkonium chloride (BAC), which is efficiently extracted into a surfactant-rich phase formed in a mixed micellar medium consisting of Triton X-114 and BAC. The stoichiometry of the extracted complex was established as (BA+)[VO(3,5-DNC)2], and the formula of its anionic component, [VO(3,5-DNC)2]\u2212, was verified by quantum-chemical calculations at the B3LYP\/6-311G level of theory and by comparison of the experimental absorption spectrum with simulated theoretical spectra. The results indicate that the thermodynamically more stable anti isomer is preferentially formed and extracted. The developed novel centrifuge-less cloud point extraction\u2013spectrophotometric method exhibits an absorption maximum at 426 nm, an apparent molar absorptivity of 1.6 \u00d7 106 L mol\u22121 cm\u22121, a limit of detection of 1.7 ng mL\u22121, and a linear range of 5.7\u201329.1 ng mL\u22121. The method was successfully applied to the determination of vanadium in spent catalysts and vanadium-based dietary supplements. Its analytical performance and sustainability were evaluated using modern assessment tools, including RGBfast.<\/jats:p>","DOI":"10.3390\/molecules31193364","type":"journal-article","created":{"date-parts":[[2026,9,22]],"date-time":"2026-09-22T08:17:54Z","timestamp":1790065074000},"page":"3364","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["First Application of 3,5-Dinitrocatechol and Benzalkonium Chloride in Cloud Point Extraction: Spectrophotometric Determination of Vanadium(V)"],"prefix":"10.3390","volume":"31","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-3941-2072","authenticated-orcid":false,"given":"Petya","family":"Racheva","sequence":"first","affiliation":[{"name":"Department of Chemical Sciences, Faculty of Pharmacy, Medical University of Plovdiv, 120 Buxton Bros Str., 4004 Plovdiv, 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Inorganic Chemistry with Methodology of Chemistry Education, Faculty of Chemistry, University of Plovdiv \u2018Paisii Hilendarski\u2019, 24 Tsar Assen St., 4000 Plovdiv, Bulgaria"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"investigation","vocabulary":"credit"},{"role":"resources","vocabulary":"credit"},{"role":"visualization","vocabulary":"credit"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8305-413X","authenticated-orcid":false,"given":"Vassil","family":"Delchev","sequence":"additional","affiliation":[{"name":"Department of Physical Chemistry, Faculty of Chemistry, University of Plovdiv \u2018Paisii Hilendarski\u2019, 24 Tsar Assen St., 4000 Plovdiv, Bulgaria"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"software","vocabulary":"credit"},{"role":"resources","vocabulary":"credit"},{"role":"writing-review-editing","vocabulary":"credit"},{"role":"project-administration","vocabulary":"credit"},{"role":"funding-acquisition","vocabulary":"credit"},{"role":"investigation","vocabulary":"credit"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0407-6171","authenticated-orcid":false,"given":"Jana","family":"\u0160andrejov\u00e1","sequence":"additional","affiliation":[{"name":"Department of Analytical Chemistry, Institute of Chemistry, Faculty of Science, Pavol Jozef \u0160af\u00e1rik University in Ko\u0161ice, Moyzesova 11, 04154 Kosice, Slovakia"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"writing-review-editing","vocabulary":"credit"},{"role":"visualization","vocabulary":"credit"},{"role":"supervision","vocabulary":"credit"},{"role":"conceptualization","vocabulary":"credit"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1360-8977","authenticated-orcid":false,"given":"Kiril","family":"Gavazov","sequence":"additional","affiliation":[{"name":"Department of Chemical Sciences, Faculty of Pharmacy, Medical University of Plovdiv, 120 Buxton Bros Str., 4004 Plovdiv, 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