ANALYSIS OF ALKYLPHENOL-BASED NONIONIC SURFACTANTS BY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY

Ethoxylated non-ionic surfactants derived from octyl- and nonylphenols were analyzed by normal-phase HPLC. A silica column (Si-100, 5 mu m) with gradient elution and UV detection at 280 nm were used for oligomer determination. Baseline separation of the ethylene oxide adducts of alkylphenols with average ethoxymer numbers as high as 40 was achieved. The elution system and the gradient profile used depend on the average ethoxymer number of the surfactant. The method can provide full information for the quantitative calculation of the oligomer distribution from ethoxylated surfactants. The hydrophobic moiety of the surfactants was characterized by reversed-phase chromatography. An octadecylsilica column (RP-18, 5 mu m) and methanol-water (8:2, v/v) as eluent were used. The procedure is useful for the rapid identification of surfactants according to the alkylphenyl chain.