{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,3]],"date-time":"2026-09-03T11:19:13Z","timestamp":1788434353917,"version":"build-2803163510"},"reference-count":31,"publisher":"American Chemical Society (ACS)","issue":"34","license":[{"start":{"date-parts":[[2026,8,19]],"date-time":"2026-08-19T00:00:00Z","timestamp":1787097600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/100014013","name":"UK Research and Innovation","doi-asserted-by":"publisher","award":["MR\/T044020\/1"],"award-info":[{"award-number":["MR\/T044020\/1"]}],"id":[{"id":"10.13039\/100014013","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100014013","name":"UK Research and Innovation","doi-asserted-by":"publisher","award":["MR\/Z000114\/1"],"award-info":[{"award-number":["MR\/Z000114\/1"]}],"id":[{"id":"10.13039\/100014013","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"published-print":{"date-parts":[[2026,9,1]]},"abstract":"<jats:title>Abstract<\/jats:title>\n                  <jats:p>We present NMR-based pH measurements in nondried commercial methanol, methanol\u2013OD, ethanol, and acetonitrile. Combining these measurements with pH gradients and spatially selective NMR enables determination of pKa and provides a highly effective tool to analyze complex molecular mixtures and identify unknown organic compounds by the functional groups present. We determine all the pKa values of alanine, glutamic acid, histidine, lysine, proline, tryptophan, and tyrosine in methanol\u2013OD, filling a major gap in the literature for these important polyprotic molecules that exhibit zwitterionic behavior. To demonstrate the potential of our method for the identification of compounds in natural mixtures, we use pH gradients to identify alkaloids and other ionizable organic compounds in unrefined extracts of hemlock (Conium maculatum), orange lichen (Xanthoria parietina), and love-in-the-mist (Nigella damascena). No chromatographic separation is necessary, highlighting how our technique could provide a fast and untargeted screening of biological samples, reaction mixtures, and digestates.<\/jats:p>","DOI":"10.1021\/acs.analchem.6c02161","type":"journal-article","created":{"date-parts":[[2026,8,19]],"date-time":"2026-08-19T15:01:22Z","timestamp":1787151682000},"page":"24921-24928","source":"Crossref","is-referenced-by-count":0,"title":["Practical pH\nMeasurements in Wet Organic Solvents\nby Gradient NMR: From Charged Amino Acid p\n                    <i>K<\/i>\n                    a to Identification of Ionizable Natural Products in Crude Extracts"],"prefix":"10.1021","volume":"98","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-5751-1827","authenticated-orcid":true,"given":"Matthew","family":"Wallace","sequence":"first","affiliation":[{"name":"University of East Anglia , , Norwich Research Park , ,","place":["Norwich, U.K., NR4 7TJ"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Serena","family":"Monaco","sequence":"additional","affiliation":[{"name":"Quadram Institute Bioscience , Norwich Research Park, Rosalind Franklin Road , ,","place":["Norwich, U.K., NR4 7UQ"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0006-4449-3451","authenticated-orcid":true,"given":"Claire F.","family":"Jones","sequence":"additional","affiliation":[{"name":"University of East Anglia , , Norwich Research Park , ,","place":["Norwich, U.K., NR4 7TJ"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Sureni","family":"Durrant","sequence":"additional","affiliation":[{"name":"University of East Anglia , , Norwich Research Park , ,","place":["Norwich, U.K., NR4 7TJ"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jothikga","family":"Dharmarajah","sequence":"additional","affiliation":[{"name":"University of East Anglia , , Norwich Research Park , ,","place":["Norwich, U.K., NR4 7TJ"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Hafsa","family":"Shafiq","sequence":"additional","affiliation":[{"name":"University of East Anglia , , Norwich Research Park , ,","place":["Norwich, U.K., NR4 7TJ"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Karim","family":"Akhtar","sequence":"additional","affiliation":[{"name":"University of East Anglia , , Norwich Research Park , ,","place":["Norwich, U.K., NR4 7TJ"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Dexter","family":"Lutsili","sequence":"additional","affiliation":[{"name":"University of East Anglia , , Norwich Research Park , ,","place":["Norwich, U.K., NR4 7TJ"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Aisosa","family":"Okunseri","sequence":"additional","affiliation":[{"name":"University of East Anglia , , Norwich Research Park , ,","place":["Norwich, U.K., NR4 7TJ"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Emily","family":"Eyo","sequence":"additional","affiliation":[{"name":"University of East Anglia , , Norwich Research Park , ,","place":["Norwich, U.K., NR4 7TJ"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4862-7999","authenticated-orcid":true,"given":"A.","family":"Ganesan","sequence":"additional","affiliation":[{"name":"Liverpool John Moores University , , Byrom Street , ,","place":["Liverpool, U.K., L3 3AF"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"316","published-online":{"date-parts":[[2026,8,19]]},"reference":[{"issue":"1","key":"2026090306480554800_cit1","doi-asserted-by":"publisher","first-page":"1","DOI":"10.1016\/S0021-9673(02)01444-9","article-title":"Influence of mobile phase acid-base equilibria on the chromatographic\nbehaviour of protolytic compounds","volume":"982","author":"Rose\u0301s","year":"2002","journal-title":"J. Chromatogr.\nA"},{"issue":"19","key":"2026090306480554800_cit2","doi-asserted-by":"publisher","first-page":"7891","DOI":"10.1021\/ic060517x","article-title":"Potentiometric titration\nof metal ions in ethanol","volume":"45","author":"Gibson","year":"2006","journal-title":"Inorg. Chem."},{"key":"2026090306480554800_cit3","doi-asserted-by":"publisher","first-page":"556","DOI":"10.1042\/bj0720556","article-title":"The alkaloids of\nhemlock (Conium maculatum L.). Distribution\nin relation to the development of the fruit","volume":"72","author":"Fairbairn","year":"1959","journal-title":"Biochem. J."},{"key":"2026090306480554800_cit4","doi-asserted-by":"publisher","first-page":"1998","DOI":"10.1039\/D3AN02000B","article-title":"A pH-enhanced\nresolution in benchtop\nNMR spectroscopy","volume":"149","author":"Putko","year":"2024","journal-title":"Analyst"},{"key":"2026090306480554800_cit5","doi-asserted-by":"publisher","first-page":"156","DOI":"10.1016\/j.jpba.2013.08.046","article-title":"Quantification of taurine in energy drinks using 1H\nNMR","volume":"93","author":"Hohmann","year":"2014","journal-title":"J. Pharm. Biomed. Anal."},{"issue":"40","key":"2026090306480554800_cit6","doi-asserted-by":"publisher","first-page":"6735","DOI":"10.1002\/ejoc.201900956","article-title":"On the Basicity of Organic Bases\nin Different Media","volume":"2019","author":"Tshepelevitsh","year":"2019","journal-title":"Eur. J. Org. Chem."},{"issue":"9","key":"2026090306480554800_cit7","doi-asserted-by":"publisher","first-page":"1407","DOI":"10.1002\/ejoc.202001649","article-title":"Strengths of Acids\nin Acetonitrile","volume":"2021","author":"Ku\u0308tt","year":"2021","journal-title":"Eur. J. Org. Chem."},{"issue":"42","key":"2026090306480554800_cit8","doi-asserted-by":"publisher","first-page":"15628","DOI":"10.1021\/acs.analchem.3c02771","article-title":"Measurement\nof the pKa Values of\nOrganic Molecules in Aqueous-Organic Solvent Mixtures by 1H NMR without\nExternal Calibrants","volume":"95","author":"Wallace","year":"2023","journal-title":"Anal. Chem."},{"issue":"9","key":"2026090306480554800_cit9","doi-asserted-by":"publisher","first-page":"2732","DOI":"10.1021\/j150327a021","article-title":"The dissociation\nof acid-base indicators in ethyl alcohol with a discussion of the\nmedium effect upon the indicator properties","volume":"35","author":"Kolthoff","year":"1931","journal-title":"Colloid Symp. Monogr."},{"issue":"4","key":"2026090306480554800_cit10","doi-asserted-by":"publisher","first-page":"613","DOI":"10.1139\/v96-065","article-title":"Solvent effect on preferred protonation\nsites in nicotinate and isonicotinate anions","volume":"74","author":"Halle\u0301","year":"1996","journal-title":"Can. J. Chem."},{"issue":"23","key":"2026090306480554800_cit11","doi-asserted-by":"publisher","first-page":"8115","DOI":"10.1021\/acs.analchem.2c00200","article-title":"Efficient p KaDetermination in a\nNonaqueous Solvent Using Chemical Shift Imaging","volume":"94","author":"Schenck","year":"2022","journal-title":"Anal. Chem."},{"issue":"6","key":"2026090306480554800_cit12","doi-asserted-by":"publisher","first-page":"1020","DOI":"10.1021\/j100824a033","article-title":"Polarographic and acid properties of thorium perchlorate in acetonitrile","volume":"65","author":"Kolthoff","year":"1961","journal-title":"J. Phys. 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Soc."},{"issue":"13","key":"2026090306480554800_cit21","doi-asserted-by":"publisher","first-page":"2579","DOI":"10.1021\/jo00363a033","article-title":"Amino acid chemistry in dipolar aprotic\nsolvents: dissociation constants and ambident reactivity","volume":"51","author":"Hughes","year":"1986","journal-title":"J. Org. Chem."},{"key":"2026090306480554800_cit22","doi-asserted-by":"publisher","DOI":"10.1017\/s0033583524000118","article-title":"Protonation constants of endo- and\nexogenous L-amino acids and their derivatives in aqueous and mixed\nsolution: Unraveling molecular secrets","volume":"57","author":"Paja\u0328k","year":"2024","journal-title":"Q. Rev.\nBiophys."},{"issue":"0","key":"2026090306480554800_cit23","doi-asserted-by":"publisher","first-page":"574","DOI":"10.1039\/tf9353100574","article-title":"The potentiometric\ntitration of non-aqueous solution\napplied to amino acids","volume":"31","author":"Ogston","year":"1935","journal-title":"Trans. Faraday Soc."},{"issue":"52","key":"2026090306480554800_cit24","doi-asserted-by":"publisher","first-page":"26954","DOI":"10.1002\/anie.202109588","article-title":"Parahydrogen Hyperpolarization\nAllows Direct NMR Detection\nof \u03b1-Amino Acids in Complex (Bio)mixtures","volume":"60","author":"Sellies","year":"2021","journal-title":"Angew. Chem., Int. Ed."},{"issue":"3","key":"2026090306480554800_cit25","doi-asserted-by":"publisher","first-page":"1518","DOI":"10.1021\/jacs.2c11285","article-title":"NMR Discrimination of d- and l-\u03b1-Amino Acids\nat Submicromolar Concentration via Parahydrogen-Induced Hyperpolarization","volume":"145","author":"Dreisewerd","year":"2023","journal-title":"J. Am. Chem. Soc."},{"issue":"1","key":"2026090306480554800_cit26","doi-asserted-by":"publisher","DOI":"10.1002\/jcc.27517","article-title":"pKa prediction\nin non-aqueous solvents","volume":"46","author":"Zheng","year":"2025","journal-title":"J. Comput. Chem."},{"issue":"7","key":"2026090306480554800_cit27","first-page":"975","article-title":"Reakce karbonylovych\nsloucenin s aminy 0.5. Polarograficka studie\nreakce cyklanonu s primarnimi aminy - rovnovazne stavy","volume":"47","author":"Brezina","year":"1953","journal-title":"Chem. Listy"},{"issue":"4","key":"2026090306480554800_cit28","doi-asserted-by":"publisher","first-page":"667","DOI":"10.1002\/jhet.5570170409","article-title":"Quinazolinone derivatives. Kinetics\nof the reaction of 2-chloromethyl-3-hydroxy-4-(3H)quinazolinone with\nnucleophiles","volume":"17","author":"Fernandez","year":"1980","journal-title":"J. Heterocycl. Chem."},{"key":"2026090306480554800_cit29","doi-asserted-by":"crossref","first-page":"633","DOI":"10.1016\/B978-0-12-044950-7.50026-X","article-title":"Appendix B - Identification\nand isolation of lichen substances","volume-title":"The\nLichens","author":"Santesson","year":"1973"},{"key":"2026090306480554800_cit30","doi-asserted-by":"publisher","first-page":"113165","DOI":"10.1016\/j.phytochem.2022.113165","article-title":"The ethnobotany,\nphytochemistry, and biological properties of Nigella damascena \u2013\nA review","volume":"198","author":"Badalamenti","year":"2022","journal-title":"Phytochemistry"},{"issue":"1","key":"2026090306480554800_cit31","doi-asserted-by":"publisher","first-page":"15","DOI":"10.1007\/s10787-999-0023-y","article-title":"Chemical\ncomposition and medicinal properties of Nigella sativa Linn","volume":"7","author":"Khan","year":"1999","journal-title":"Inflammopharmacology"}],"container-title":["Analytical Chemistry"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/pubs.acs.org\/doi\/pdf\/10.1021\/acs.analchem.6c02161","content-type":"application\/pdf","content-version":"vor","intended-application":"unspecified"},{"URL":"https:\/\/pubs.acs.org\/ancham\/article-pdf\/98\/34\/24921\/66879062\/acs.analchem.6c02161.pdf","content-type":"application\/pdf","content-version":"vor","intended-application":"syndication"},{"URL":"https:\/\/pubs.acs.org\/ancham\/article-pdf\/98\/34\/24921\/66879062\/acs.analchem.6c02161.pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,9,3]],"date-time":"2026-09-03T10:48:14Z","timestamp":1788432494000},"score":1,"resource":{"primary":{"URL":"https:\/\/pubs.acs.org\/ancham\/article\/98\/34\/24921\/5276661\/Practical-pH-Measurements-in-Wet-Organic-Solvents"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,8,19]]},"references-count":31,"journal-issue":{"issue":"34","published-online":{"date-parts":[[2026,8,19]]},"published-print":{"date-parts":[[2026,9,1]]}},"URL":"https:\/\/doi.org\/10.1021\/acs.analchem.6c02161","relation":{},"ISSN":["0003-2700","1520-6882"],"issn-type":[{"value":"0003-2700","type":"print"},{"value":"1520-6882","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,8,19]]}}}