Ion Exclusion Chromatography is based on the electrostatic repulsion between ionic analytes and charged sites on the stationary phase. Unlike Ion Exchange Chromatography, which relies on electrostatic attraction, IEC uses exclusion effects to control analyte migration through the column.
In this technique, a weakly acidic cation-exchange resin — typically in the hydrogen or sodium form — serves as the stationary phase. Strongly dissociated ions are repelled from the charged resin surface and elute first, while weak acids, alcohols, and neutral molecules diffuse partially into the resin pores and elute later.
Because separation is driven by differences in ionization degree and molecular size, IEC is widely used for the determination of organic acids, alcohols, sugars, and inorganic anions in food chemistry, fermentation control, environmental analysis, and water quality testing.
It is a robust, reproducible, and environmentally friendly method that employs aqueous eluents and requires minimal sample preparation.
Ion Exclusion Chromatography is a specialized mode of liquid chromatography designed for the separation of weakly ionized or neutral polar compounds. It provides an effective alternative to Ion Exchange and Reversed Phase Chromatography when analytes exhibit similar polarity but differ in ionization behavior.
Due to its mild, aqueous operating conditions and absence of strong organic solvents, IEC is well-suited for industrial, biochemical, and environmental applications where sample integrity and reproducibility are critical.
The stationary phase in Ion Exclusion Chromatography typically consists of crosslinked polystyrene–divinylbenzene (PS/DVB) cation-exchange resins in the hydrogen or sodium ionic form. These resins possess sulfonic acid functional groups, which create a negatively charged surface that repels anions and partially excludes weak acids and neutrals.
The pore structure and degree of crosslinking define the permeation range and exclusion efficiency, enabling fine control over retention for various organic acids, sugars, and alcohols. The high mechanical stability and chemical resistance of PS/DVB resins ensure consistent performance across a wide range of aqueous eluents and operating temperatures.
The mobile phase in IEC is purely aqueous, typically containing dilute mineral acids (e.g., sulfuric or phosphoric acid) to maintain protonation of the stationary phase and suppress analyte ionization.
The eluent strength is mild, ensuring non-destructive separations and long column lifetime. Since no organic modifiers or high-ionic-strength buffers are required, the method is environmentally friendly and compatible with conductivity, refractive index (RI), or UV detection.
Elution order is influenced by the analyte’s pKa, molecular size, and degree of dissociation, allowing effective separation of organic acids, alcohols, and neutral compounds in complex aqueous mixtures.
Retention in Ion Exclusion Chromatography is governed by electrostatic repulsion and size exclusion. Strong electrolytes are excluded from the charged resin pores and elute first, while weak acids and neutral species penetrate partially and elute later.
This mechanism provides a clear distinction between ionic and non-ionic components without the need for gradient elution or ion-pairing reagents. The technique delivers excellent reproducibility, low solvent consumption, and stable calibration behavior — ideal for routine quantitative analysis.
| Name | Particle Sizes | Carbon Load | Pore Size |
|---|---|---|---|
| ReproGel Ca | 9 µm | ||
| ReproGel H | 9 µm | ||
| ReproGel K | 9 µm | ||
| ReproGel Na | 9 µm | ||
| ReproGel Pb | 9 µm | ||
| Repromer Ca | 9 µm | ||
| Repromer H | 9 µm | ||
| Repromer K | 9 µm | ||
| Repromer Na | 9 µm | ||
| Repromer Pb | 9 µm | ||
| Grom Resin Ca++, IEX | 8 µm | ||
| Grom Resin H+, IEX | 8 µm | ||
| Grom Resin Na++, IEX | 8 µm | ||
| Grom Resin Pb++, IEX | 8 µm |