Comparison of the Binding Constant of Decanesulfonate with β-Cyclodextrin as Determined by Liquid Chromatography with a Water Mobile Phase and Flow Injection Analysis Coupled with Dynamic Surface Tension Detection

✍ Scribed by Toby E. Young; Keith E. Miller; Robert E. Synovec

• Publisher: Elsevier Science
• Year: 1999
• Tongue: English
• Weight: 92 KB
• Volume: 62
• Category: Article
• ISSN: 0026-265X
• DOI: 10.1006/mchj.1999.1720

✦ Synopsis

This paper compares two independent methods for the determination of the inclusion complex binding constant between ␤-cyclodextrin (␤-CD) and decanesulfonate. First, reverse-phase liquid chromatography (RP-LC) separations of four surfactants are examined under two conditions for the binding constant determination. The first separation relies on RP-LC using a 100% water mobile phase and a cyanopropyl stationary phase. Hexanesulfonate, octyl sulfate, and decanesulfonate were separated in under 10 min. With the addition of only 1 mM ␤-CD to the water mobile phase, the same three surfactants, in addition to dodecyl sulfate, were separated in 6 min. Limits of detection were in the parts-per-billion range using conductivity detection but did not require a mobile phase conductivity suppressor. The binding constant for decanesulfonate with ␤-CD using RP-LC with a water mobile phase was found to be (3.13 Ϯ 0.38) ϫ 10 3 M Ϫ1 . Second, flow injection analysis (FIA) is coupled with dynamic surface tension detection (DSTD) to provide an independent method to determine the binding constant of ␤-CD with decanesulfonate. Using FIA with DSTD, a decanesulfonate binding constant with ␤-CD of (4.75 Ϯ 1.25) ϫ 10 3 M Ϫ1 was obtained. The two binding constant values were in close agreement, suggesting that secondary equilibria were minimal in RP-LC with a water mobile phase. The combination of FIA with DSTD is shown to be an excellent method to help study reverse-phase retention mechanisms involving complexation equilibria.