{"id":14540,"date":"2022-03-15T07:34:24","date_gmt":"2022-03-15T07:34:24","guid":{"rendered":"https:\/\/each.ut.ee\/EACH\/?p=14540"},"modified":"2024-08-03T16:30:09","modified_gmt":"2024-08-03T16:30:09","slug":"quantifying-acidity-in-heterogeneous-systems-biphasic-pka-values","status":"publish","type":"post","link":"https:\/\/each.ut.ee\/EACH\/quantifying-acidity-in-heterogeneous-systems-biphasic-pka-values\/","title":{"rendered":"Quantifying acidity in heterogeneous systems: Biphasic pKa values"},"content":{"rendered":"\n

As a result of a recent development in our group, it is now, for the first time, possible to rigorously measure acidity of acids in biphasic systems (aqueous phase at equilibrium with a water-immiscible phase) by using biphasic pK<\/em>a<\/sub> values (pK<\/em>a<\/sub>ow<\/sup> values). This work has now been published in Analytical Chemistry<\/em> 2022<\/strong>, 94<\/em>, 4059\u20134064<\/a>.<\/p>\n\n\n\n

Two EACH students \u2013 Anh Hai Vu<\/strong> and Thuong Hoai Nguyen<\/strong> \u2013 made significant contribution to this work during their studies at Tartu. Congratulations, Anh and Thuong!<\/p>\n\n\n\n

\n
\"\"<\/a>
Anh Hai Vu<\/figcaption><\/figure>\n\n\n\n
\"\"<\/a>
Thuong Hoai Nguyen<\/figcaption><\/figure>\n<\/figure>\n\n\n\n
\"\"<\/a><\/figure><\/div>\n\n\n\n

In this work, the octanol-water biphasic pK<\/em>a<\/sub>ow<\/sup> values have been determined for 35 acids of various structures and chemical properties (carboxylic acids, phenols, diphenylamines, imides, different CH acids) using UV-Vis and NMR (1<\/sup>H, 13<\/sup>C, or 31<\/sup>P) spectrometry.<\/p>\n\n\n\n

Biphasic pK<\/em>a<\/sub> values enable quantifying acid dissociation in biphasic systems in a more realistic and rigorous way than the conventional \u201cmono-phasic\u201d pK<\/em>a<\/sub> values. The latter completely ignores a large part of the picture \u2013 partitioning of the neutrals and the ions between the two phases and ion-pairing in the low-polarity phase. In contrast, pK<\/em>a<\/sub>ow<\/sup> values account for these effects. The ratio of the acid and its conjugate base is measured in the 1-octanol phase, using UV-Vis and\/or NMR spectrometric method. The activity of H+<\/sup> is measured in the aqueous phase with a conventional pH-meter. The pK<\/em>a<\/sub>ow<\/sup> values are obtained at different concentrations and extrapolated to zero concentration.<\/p>\n\n\n\n

Biphasic systems are present in many biological and technological systems and processes: cell membranes, solvent extraction, phase-transfer catalysis, sensor membranes, etc. In all such systems, acid-base properties of the participating compounds would be best described using biphasic rather than \u201cmono-phasic\u201d pK<\/em>a<\/sub> values.<\/p>\n","protected":false},"excerpt":{"rendered":"

As a result of a recent development in our group, it is now, for the first time, possible to rigorously measure acidity of acids in biphasic systems (aqueous phase at equilibrium with a water-immiscible phase) by using biphasic pKa values (pKaow values). This work has now been published in Analytical Chemistry 2022, 94, 4059\u20134064. Two […]<\/p>\n","protected":false},"author":23,"featured_media":14544,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"ngg_post_thumbnail":0,"footnotes":""},"categories":[1],"tags":[],"class_list":["post-14540","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-uncategorized"],"blocksy_meta":[],"_links":{"self":[{"href":"https:\/\/each.ut.ee\/EACH\/wp-json\/wp\/v2\/posts\/14540","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/each.ut.ee\/EACH\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/each.ut.ee\/EACH\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/each.ut.ee\/EACH\/wp-json\/wp\/v2\/users\/23"}],"replies":[{"embeddable":true,"href":"https:\/\/each.ut.ee\/EACH\/wp-json\/wp\/v2\/comments?post=14540"}],"version-history":[{"count":2,"href":"https:\/\/each.ut.ee\/EACH\/wp-json\/wp\/v2\/posts\/14540\/revisions"}],"predecessor-version":[{"id":14546,"href":"https:\/\/each.ut.ee\/EACH\/wp-json\/wp\/v2\/posts\/14540\/revisions\/14546"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/each.ut.ee\/EACH\/wp-json\/wp\/v2\/media\/14544"}],"wp:attachment":[{"href":"https:\/\/each.ut.ee\/EACH\/wp-json\/wp\/v2\/media?parent=14540"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/each.ut.ee\/EACH\/wp-json\/wp\/v2\/categories?post=14540"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/each.ut.ee\/EACH\/wp-json\/wp\/v2\/tags?post=14540"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}