Surface characterization of okra hydrocolloid extract by inverse gas chromatography (IGC)

•Okra hydrocolloid extract was studied using inverse gas chromatography (IGC).•The thermodynamic components of the adsorption were calculated.•The okra extract matrix is Lewis amphoteric with predominantly basic character.•The above are discussed in conjunction with data from other analytical methods.

An extensive surface characterization of okra hydrocolloid extract was conducted by means of inverse gas chromatography (IGC) at infinite dilution in three temperatures (40, 50, 60 °C). The specific retention volume of 14 solvents, used as probes, was utilized for the assessment of the surface energy, the free energy of adsorption, as well as the relevant enthalpy and entropic component. The contribution to the surface energy of okra extract decreases with increasing temperature. Furthermore, surface characterization demonstrated that the okra extract matrix is Lewis amphoteric with predominantly basic character, as confirmed by the acidity and basicity constants KA and KB, respectively. The above were discussed in conjunction with X-ray diffractometry (XRD), size exclusion chromatography (SEC–MALLS/UV), and Fourier transform infra-red spectroscopy (FTIR) data.

Graphical abstractEnergy of adsorption of n-alkanes and polar probes versus their boiling temperatures on the surface of okra extract, at 40 °C.Figure optionsDownload full-size imageDownload as PowerPoint slide