Non-aqueous capillary electrophoresis of nonylphenol ethoxylates and their lipophilic metabolites

PAOLA A. BABAY, RAQUEL T. GETTAR, MARÍA F. SILVA, BJÖRN THIELE, DANIEL A. BATISTONI

JOURNAL OF CHROMATOGRAPHY - A

Elsevier

Año: 2006 vol. 1116 p. 277 - 285

0021-9673

Capillary electrophoresis based on non-aqueous solvent background electrolytes was employed, with single and multiple wavelength UV detection, to evaluate discrimination among oligomer components of mixtures of non-ionic, long chain nonylphenol ethoxylates (NPnEO, withnEO, with n = number of ethoxy units) and their lipophilic degradation products. The tested organic solvents included acetonitrile, methanol, ethanol, 1- and 2-propanol, 1-butanol and tetrahydrofurane in the presence of sodium acetate. A rational variation of composition of background electrolyte solvent mixtures allowed to modify the mobility of electroosmotic flow and the type and degree of interactions between the ionic additive (sodium acetate) and the components of the analyte mixtures. The physicochemical properties of the solvents, such as dielectric constant, viscosity and electron donor?acceptor ability regarding the additive, were considered to improve the resolution of lipophilic compounds with less than three ethoxy groups and the discrimination attainable for longer chain oligomers. The studied methodologies also allowed discerning between surfactants of similar (nominal) ethoxy chain lengths. This was demonstrated by the different peak distribution patterns observed for NPnEO compounds with 2-propanol, 1-butanol and tetrahydrofurane in the presence of sodium acetate. A rational variation of composition of background electrolyte solvent mixtures allowed to modify the mobility of electroosmotic flow and the type and degree of interactions between the ionic additive (sodium acetate) and the components of the analyte mixtures. The physicochemical properties of the solvents, such as dielectric constant, viscosity and electron donor?acceptor ability regarding the additive, were considered to improve the resolution of lipophilic compounds with less than three ethoxy groups and the discrimination attainable for longer chain oligomers. The studied methodologies also allowed discerning between surfactants of similar (nominal) ethoxy chain lengths. This was demonstrated by the different peak distribution patterns observed for NPnEO compounds with = number of ethoxy units) and their lipophilic degradation products. The tested organic solvents included acetonitrile, methanol, ethanol, 1- and 2-propanol, 1-butanol and tetrahydrofurane in the presence of sodium acetate. A rational variation of composition of background electrolyte solvent mixtures allowed to modify the mobility of electroosmotic flow and the type and degree of interactions between the ionic additive (sodium acetate) and the components of the analyte mixtures. The physicochemical properties of the solvents, such as dielectric constant, viscosity and electron donor?acceptor ability regarding the additive, were considered to improve the resolution of lipophilic compounds with less than three ethoxy groups and the discrimination attainable for longer chain oligomers. The studied methodologies also allowed discerning between surfactants of similar (nominal) ethoxy chain lengths. This was demonstrated by the different peak distribution patterns observed for NPnEO compounds withnEO compounds with n = 7.5 and 10, respectively.= 7.5 and 10, respectively.