Work

Modeling indirectly detected analyte peaks in ion-pair reversed-phase chromatography

Year: 2024

Type: article

Abstract: • Indirect peaks simulated using mechanistic models with adsorption isotherm data. • For analytes and probes of the same charge, the bi-Langmuir model was used. • For oppositely charged analytes and probes, a modified bi-Langmuir model was used. • The modified bi-Langmuir model accounted for ion-pairing on the surface. • Excellent agreement between observed and predicted analytical method sensitivity. In indirect detection, sample components lacking detectable properties are detected by adding a detectable component to the eluent, a so-called probe that interacts with the analytes to be detected. This study focuses on modeling indirect detection in two principally different cases. In case (1), the analyte component has the same charge as the probe component, so the probe acts as a co-ion of the analyte. In case (2), the analyte component has the opposite charge to the probe, so the probe acts as a counter-ion of the analyte. In the co-ion case (1), the analytes are alkyl sulfonates, and a competitive bi-Langmuir isotherm model was used. In the counter-ion case (2), the analytes are amines, and a modified bi-Langmuir isotherm model, incorporating ion-pairing on the stationary phase surface, was derived and applied for simulating the elution profiles. The chromatographic system comprised an XBridge Phenyl column as the stationary phase and an acetonitrile/phosphate buffer mixture with varying concentrations of sodium 2-naphthalenesulfonate as the eluent. In both cases, the detectable probe component was sodium 2-naphthalenesulfonate. The applied isotherm models successfully predicted system peaks with high agreement in both model cases, with calculated relative errors in retention times typically below 4.72 % and often below 1 %. The models were employed to predict the sensitivity of analytical methods, demonstrating excellent agreement between experimental and calculated sensitivities. These findings confirm the validity of the new adsorption isotherm model under these experimental conditions.

Source: Journal of Chromatography A

DOI: 10.1016/j.chroma.2024.465550

Authors: Marek Leśko, Gergely Szabados, Torgny Fornstedt, Jörgen Samuelsson

Institution: Karlstad University

Language: English

Topic: Analytical Chemistry and Chromatography

Subfield: Spectroscopy

Field: Chemistry

Domain: Physical Sciences

Open Access status: hybrid

Estimated APC paid: $3,630

Funder: Stiftelsen för Kunskaps- och Kompetensutveckling