Ion Chromatography

The suppressor is a post-column reactor that chemically converts the excess eluent salt (background ions) into a weakly ionized compound, dramatically reducing the background conductivity. This suppression allows the detector to measure small ion peaks with high sensitivity and contrast against a very low baseline, improving both detection limits and peak resolution.

Use an anion-exchange column (negatively charged resin) to separate negatively charged ions (anions such as chloride, nitrate, phosphate, sulfate). Use a cation-exchange column (positively charged resin) to separate positively charged ions (cations such as sodium, potassium, calcium, magnesium). Some laboratories run both methods to obtain a complete ionic profile of a sample.

Peak tailing (asymmetrical peak shape) often results from secondary interactions between the analyte and residual silanol groups on the column packing, especially when the sample contains ions at high concentration or when the column is not properly buffered. Using buffered eluents and properly conditioned columns minimizes this effect.

Yes. Ion chromatography can separate organic anions (acetate, citrate, oxalate) and organic cations (ammonium, tetramethylammonium) using appropriately selected columns and eluents. However, organic molecules without ionic groups are typically not retained and will not be separated or detected.

Gradient elution involves progressively increasing the concentration of the eluent salt during the run, causing ions with weak column affinity to elute early and ions with strong affinity to elute later. This improves separation of analytes with diverse ion-exchange affinities and reduces overall analysis time compared to isocratic (constant eluent concentration) methods.