Simultaneous separation of nonionic surfactants and polyethylene glycols by reversed phase high performance liquid chromatography

Abstract

The simultaneous separation of polyethylene glycol and its derivatives such as the lauryl alcohol and lauric acid ethoxylate oligomers was carried out by reversed phase high performance liquid chromatography. Branched fluorinated silica gel columns combined with evaporative light scattering detection were used for the characterization of nonionic surfactants. Lauryl alcohol ethoxylate oligomers were separated at 10 ~ with an isocratic eluent according to ethoxylate number and the retention time of the oligomers decreases with increasing ethoxylate number. The Van't Hoffplots of retention factor of lauryl alcohol ethoxylate gave a complex cure, which is anomalous behavior for reversed phase high performance liquid chromatography. The anomalous Van't Holt plots were explained by a partial conformational change from polar to less polar conformers with increasing temperature. The most significant features for the analysis of the lauryl alcohol ethoxylate were the use of acetonitrile as mobile phase and operating temperature. The polyethylene glycol was separated according to ethoxylate number and the retention time of oligomers increased with increasing ethoxylate number. The Van't Hoffplots of retention factor of polyethylene glycol had negative slopes. It was presumed that the polar conformation of the ethylene oxide chain decreased with increasing temperature. The lauryl alcohol ethoxylate and polyethylene glycol were separated simultaneously in gradient elution as a result of the conformational change of the ethylene oxide chain. As a practical example, lauric acid ethoxylate simultaneously separated into free polyethylene glycol, ethoxylate monolaurate and ethoxylate dilaurate in gradient elution.

Retention of 3,5-dinitrobenzoyl derivatives of linear alcohol polyethoxylates in reversed-phase liquid chromatographic system with acetonitrile–water mobile phase

“…The processes mentioned in the introduction might be the cause of the irregular behaviour of LAEs. The shift in conformer equilibrium [8][9][10] to less polar conformer(s) of oxyethylene chain that shows higher retention in reversed-phase system, the rise of interaction between oxyethylene chain and residual silanol groups [10] as well as the changes in solvatation of oxyethylene chain [12] with the lowering of water content, each of these processes can lead to the described retention behaviour of derivatised LAEs.…”

“…impossibility to calculate changes of entropy). Kamiusuki et al [10] also explained anomalous retention behaviour of lauryl alcohol ethoxylates on polyfluoroalkylsilane coated silica gel column by mentioned conformational change. Differences between separation of the studied compounds on endcapped and non-endcapped columns they ascribed to the interaction of the oxyethylene chain with residual silanols.…”

Separation of fatty alcohol polyethoxylates by capillary electrophoresis through easy electroosmotic flow control with a quaternary diammonium salt

“…The polyoxyethylene chain forms weak association complexes with potassium ion, thus allowing the 3,5-dinitrobenzoyl chloride derivatives to be also separated on a cation-exchange column [10,11]. Underivatised FAEs can be analysed in industrial samples using either a refractive index [12][13][14][15] or evaporative-light scattering detection (ELSD) [13,[16][17][18][19][20]. Supercritical fluid chromatography with ELSD has been also described [21].…”

Packed column supercritical fluid chromatography of oligoethers using pure carbon dioxide with flame ionization and ultraviolet detection

“…There appears to be a growing interest in analyzing some such homologous series using normal phase HPLC with light scattering detection [11,12], in part because UV at low wavelengths is not considered to be compatible with HPLC gradients [12]. A number of derivatization schemes have also been developed [i.e.…”