06928 IUPAC Gold Book - mass distribution ratio 10.1351/goldbook.MT06928 MT06928 current quantity 1 Defined as: \[k_{\rm{MEKC}} = \frac{n_{\rm{mc}}}{n_{\rm{aq}}} = K\cdot \frac{V_{\rm{mc}}}{V_{\rm{aq}}}\] where \(n_{\rm{mc}}\) and \(n_{\rm{aq}}\) are the chemical amounts of the analyte in the micellar and aqueous phases, respectively, \(K\) is the distribution constant and \(V_{\rm{mc}}\) and \(V_{\rm{aq}}\) are the corresponding volumes of the phases. In the case of an electrically neutral analyte, \(k_{\rm{MEKC}}\) can be calculated directly from the migration times: \[k_{\rm{MEKC}} = \frac{t_{\rm{m}} - t_{\rm{eo}}}{t_{\rm{eo}}(1 - t_{\rm{m}}/t_{\rm{mc}})}\] \(k_{\rm{MEKC}}\) should not be confused with the retention factor (in column chromatography) \(k\). However, \(k_{\rm{MEKC}}\) is analogous to the mass distribution ratio (in chromatography). analyte https://goldbook.iupac.org/terms/view/A00331 chromatography https://goldbook.iupac.org/terms/view/C01075 column chromatography https://goldbook.iupac.org/terms/view/C01182 distribution constant https://goldbook.iupac.org/terms/view/D01813 mass distribution ratio https://goldbook.iupac.org/terms/view/E02305 migration https://goldbook.iupac.org/terms/view/M03920 PAC, 2004, 76, 443. 'Terminology for analytical capillary electromigration techniques (IUPAC Recommendations 2003)' on page 449 (https://doi.org/10.1351/pac200476020443) https://goldbook.iupac.org/terms/view/MT06928/html https://goldbook.iupac.org/terms/view/MT06928/json https://goldbook.iupac.org/terms/view/MT06928/plain Citation: 'mass distribution ratio' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. 10.1351/goldbook.MT06928 The IUPAC Gold Book is licensed under Creative Commons Attribution-ShareAlike CC BY-SA 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) for individual terms. If you are interested in licensing the Gold Book for commercial use, please contact the IUPAC Executive Director at executivedirector@iupac.org . The International Union of Pure and Applied Chemistry (IUPAC) is continuously reviewing and, where needed, updating terms in the Compendium of Chemical Terminology (the IUPAC Gold Book). Users of these terms are encouraged to include the version of a term with its use and to check regularly for updates to term definitions that you are using. 2026-07-26T04:49:22+00:00