Effect of increasing concentration of ammonium acetate as an additive in supercritical fluid chromatography using CO₂-methanol mobile phase

• Published in: Journal of Chromatography A Vol. 1216; no. 36; pp. 6441 - 6450
• Main Authors: Cazenave-Gassiot, Amaury, Boughtflower, Robert, Caldwell, Jeffrey, Hitzel, Laure, Holyoak, Claire, Lane, Stephen, Oakley, Paul, Pullen, Frank, Richardson, Stefan, Langley, G. John
• Format: Journal Article
• Language: English
• Published: Amsterdam Amsterdam; New York: Elsevier 04.09.2009; Elsevier
• Subjects: Acetates; Analysis; Analytical chemistry; Anti-Inflammatory Agents, Non-Steroidal - analysis; Antihypertensive Agents - analysis; Atenolol - analysis; Biological and medical sciences; Carbon Dioxide; Chemistry; Chromatographic methods and physical methods associated with chromatography; Chromatography, High Pressure Liquid; Chromatography, Supercritical Fluid; Diltiazem - analysis; Exact sciences and technology; General pharmacology; Mass Spectrometry; Medical sciences; Methanol; Naproxen - analysis; Other chromatographic methods; Pharmacology. Drug treatments; Pyridines - chemistry; Silicon Dioxide - chemistry; Sulfonamides - analysis; Surface Properties; Peak resolution; Additives; Aminoalcohol; Line shape; Sulfonamide; Phase composition; Chromatographic retention; Carbon dioxide; Benzothiazepine derivatives; Retention factor; Atenolol; Diltiazem; Mobile phase; Retention time; Supercritical fluid chromatography; Ultraviolet detector; Naproxen; Tertiary amine; Ammonium Acetate; Arylpropionic acid derivatives; Methanol
• ISSN: 0021-9673; 1873-3778
• DOI: 10.1016/j.chroma.2009.07.022

The effects of increasing concentrations of ammonium acetate additive in supercritical fluid chromatography were studied on silica, 2-ethyl-pyridine and endcapped 2-ethyl-pyridine stationary phases. The study involved the addition of increasing concentrations of the ammonium acetate either in the mobile phase modifier (methanol) or in the sample solvent. The effects of ammonium acetate on retention and peak shape of the analytes were evaluated. Compounds that exhibited satisfactory chromatographic behaviour in the absence of the additive were virtually unaffected by its presence in the mobile phase or sample solvent. Nevertheless, compounds that exhibited late elution and strongly tailing peak shapes when pure methanol was used showed dramatically improved chromatographic behaviour in the presence of the additive. Shorter retention was observed not only when the modifier was introduced in the mobile phase but also when it was in the sample solvent.