Effect of ionic additives on the elution of sodium aryl sulfonates in supercritical fluid chromatography.
Addition of a small amount of polar solvent (i.e., modifier) to CO2 in packed column supercritical fluid chromatography (SFC) has shown major improvements in both polar analyte solubility and interaction of the polar analyte with the stationary phase. Recently, the addition of an ionic component (i.e., additive) to the primary modifier by one of us has been shown to extend even further the application of SFC to polar analytes. In this work, the effect of various ionic additives on the elution of ionic compounds, such as sodium 4-dodecylbenzene sulfonate and sodium 4-octylbenene sulfonate, has been studied. The additives were lithium acetate, ammonium acetate, tetramethylammonium acetate, tetrabutylammonium acetate, and ammonium chloride dissolved in methanol. Three stationary phases with different degrees of deactivation were considered: conventional cyanopropyl, deltabond cyanopropyl, and bare silica. The effect of additive concentration and additive functionality on analyte retention was investigated. Sodium 4-dodecylbenzene sulfonate was successfully eluted using all the additives with good peak shape under isocratic/isobaric/isothermal conditions. Different additives, however, yielded different retention times and in some cases different peak shapes.
Zheng
J
J
Department of Chemistry, University College of Science, Virginia Polytechnic Inst. and State, 107 Davidson Hall, Virginia Tech Blacksburg, VA 24061-0212, USA.
Taylor
L T
LT
Pinkston
J David
JD
Mangels
M L
ML
D000085:Acetates / Q000737:chemistry; D001557:Benzenesulfonates / Q000302:isolation & purification*; D025924:Chromatography, Supercritical Fluid / Q000379:methods*; D013058:Mass Spectrometry; D000432:Methanol / Q000737:chemistry; D000644:Quaternary Ammonium Compounds / Q000737:chemistry; D012997:Solvents / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet
D000085:Acetates; D001557:Benzenesulfonates; D000644:Quaternary Ammonium Compounds; D012997:Solvents; C001114:dodecylbenzenesulfonic acid; C488804:lithium acetate; D000432:Methanol