Sulfonium and phosphonium, new ion-pairing agents with unique selectivity towards polarizable anions

• Published in: Journal of Chromatography A Vol. 1113; no. 1; pp. 123 - 129
• Main Authors: Harrison, Christopher R., Sader, Jayden A., Lucy, Charles A.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 28-04-2006; Elsevier
• Subjects: Analytical chemistry; Anion; Anions; Chaotropic; Chemistry; Chromatographic methods and physical methods associated with chromatography; Exact sciences and technology; Hofmeister series; Indicators and Reagents; Ion-pair chromatography; Ion-pairing; Kosmotropic; Organophosphorus Compounds - chemistry; Other chromatographic methods; Perchlorate; Sensitivity and Specificity; Sulfonium Compounds - chemistry; Tetrabutylphosphonium; Tributylsulphonium; Tributylsulphonium; Perchlorate; Chaotropic; Tetrabutylphosphonium; Hofmeister series; Ion-pair chromatography; Ion-pairing; Kosmotropic; Anion; Organic cation; HPLC chromatography; Selectivity; Mobile phase; Ion interaction chromatography; Phosphorus Organic compounds; Quaternary phosphonium compound; Chaotropic anion; Sulfonium compound; Phase composition; Ion pair; Retention factor; Perchlorates; Electrochemical detector; Reversed phase chromatography; Inorganic anion; Conductometry
• ISSN: 0021-9673
• DOI: 10.1016/j.chroma.2006.01.132

Ion-pair chromatography (IPC) almost universally relies upon ammonium-based ion-pairing agents (IPAs) for anion separations. This work compares tetrabutylammonium (TBA) with tetrabutylphosphonium (TBP) and tributylsulfonium (TBS). To best understand the retention behavior analytes used for characterization of the IPAs spanned the Hofmeister series; from kosmotropic monoanions (iodate, chloride, nitrite) and intermediate anions (nitrate, bromide) to chaotropic ions (perchlorate, thiocyanate, iodide). The studies demonstrate that tetrabutylphosphonium is the most chaotropic IPA, followed by tetrabutylammonium and finally tributylsulfonium is the least chaotropic. In the case of the chaotropic anions, the retention of perchlorate was least with tributylsulfonium, and greatest for tetrabutylphosphonium, with tetrabutylammonium being intermediate. The multivalent kosmotropic anions (sulfate, chromate, thiosulfate) demonstrated unique selectivity changes depending on the kosmotropic/chaotropic nature of the IPA. Demonstrating increases in retention with increasing IPA concentration only with tributylsulfonium, whereas the more chaotropic IPAs universally decreased the retention of the multivalent anions.