09932 IUPAC Gold Book - Brownian field-flow fractionation mode 10.1351/goldbook.09932 09932 current initialism: BFFF synonyms: BFFF mode, NFFF mode, normal FFF, normal FFF mode (NFFF) 1 Mechanism of field-flow fractionation of sub-micron particles that relies on Brownian motion. BFFF mode requires a specific sample injection procedure described as stop-flow injection or a relaxation step. A relaxation time is needed to equilibrate the sample under the influence of a force field and Brownian diffusion in the absence of flow. The injected sample is forced to concentrate in a thin layer adjacent to the accumulation wall (channel bottom). When the flow is switched on, elution begins with smaller particles, which are distributed further away from the accumulation wall and thus protrude further into the faster flow streams; larger particles elute later. Two main factors influencing the sample behaviour in BFFF mode are the properties of particles characterized by the diffusion coefficient and the strength of the cross-field applied. elution https://goldbook.iupac.org//terms/view/09943 field-flow fractionation https://goldbook.iupac.org//terms/view/09934 PAC, 2017, 90, 181. 'Terminology of separation methods (IUPAC Recommendations 2017)' on page 220 (https://doi.org/10.1515/pac-2017-0111) https://goldbook.iupac.org/terms/view/09932/html https://goldbook.iupac.org/terms/view/09932/json https://goldbook.iupac.org/terms/view/09932/plain Citation: 'Brownian field-flow fractionation mode' 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.09932 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. 2026-04-19T06:01:07+00:00