Unifying sorption isotherms in reversed-phase liquid chromatography

TY - JOUR

T1 - Unifying sorption isotherms in reversed-phase liquid chromatography

AU - Heamen, William

AU - Matubayasi, Nobuyuki

AU - Sneddon, Helen

AU - Shimizu, Seishi

N1 - © 2025 Elsevier B.V. This is an author-produced version of the published paper. Uploaded in accordance with the University’s Research Publications and Open Access policy.

PY - 2025/6/21

Y1 - 2025/6/21

N2 - The use of adsorption isotherm models has contributed to understanding retention in chromatography. However, the common isotherm models (such as Langmuir, BET, and GAB) assume site-specific, layer-by-layer adsorption on a uniform surface, which is at odds with the reality of chromatographic interfaces (heterogeneous surfaces with sorbate mobility and adsorption-partitioning duality). Our goal is to clarify the interactions underlying chromatographic retention while overcoming the above contradiction caused by the overly idealized or unrealistic assumptions of the traditional isotherm models. This can be achieved by the statistical thermodynamic fluctuation theory and the ABC isotherm derived from it, which is capable not only of capturing the mono-, di-, and tri-sorbate interactions as its parameters but also of encompassing the Langmuir, BET, GAB, and even anti-Langmuir isotherm models as its special cases. We demonstrate how the parameters from the traditional models can be reinterpreted via sorbate interactions. The sorbate-sorbate interaction plays a key role in elucidating the origin of different IUPAC isotherm types: Type I (convex upward) and Type III (convex downward) represent the opposite end of sorbate-sorbate repulsion and attraction that are independent of sorbate concentration, whereas Type II lies in-between, in which sorbate-sorbate interaction, which is repulsive at low concentration, turns attractive once sufficient quantity of sorbate is present at the interface (convex upward to convex downward).

AB - The use of adsorption isotherm models has contributed to understanding retention in chromatography. However, the common isotherm models (such as Langmuir, BET, and GAB) assume site-specific, layer-by-layer adsorption on a uniform surface, which is at odds with the reality of chromatographic interfaces (heterogeneous surfaces with sorbate mobility and adsorption-partitioning duality). Our goal is to clarify the interactions underlying chromatographic retention while overcoming the above contradiction caused by the overly idealized or unrealistic assumptions of the traditional isotherm models. This can be achieved by the statistical thermodynamic fluctuation theory and the ABC isotherm derived from it, which is capable not only of capturing the mono-, di-, and tri-sorbate interactions as its parameters but also of encompassing the Langmuir, BET, GAB, and even anti-Langmuir isotherm models as its special cases. We demonstrate how the parameters from the traditional models can be reinterpreted via sorbate interactions. The sorbate-sorbate interaction plays a key role in elucidating the origin of different IUPAC isotherm types: Type I (convex upward) and Type III (convex downward) represent the opposite end of sorbate-sorbate repulsion and attraction that are independent of sorbate concentration, whereas Type II lies in-between, in which sorbate-sorbate interaction, which is repulsive at low concentration, turns attractive once sufficient quantity of sorbate is present at the interface (convex upward to convex downward).

KW - Adsorption isotherms

KW - BET

KW - Langmuir

KW - RPLC retention

KW - Sorbate-sorbate interactions

UR - http://www.scopus.com/inward/record.url?scp=105002556089&partnerID=8YFLogxK

U2 - 10.1016/j.chroma.2025.465891

DO - 10.1016/j.chroma.2025.465891

M3 - Article

AN - SCOPUS:105002556089

SN - 0021-9673

VL - 1751

JO - Journal of Chromatography A

JF - Journal of Chromatography A

M1 - 465891

ER -