HOMOLOG SEPARATION OF LINEAR ALCOHOL ETHOXYLATES BY HIGHPERFORMANCE LIQUID-CHROMATOGRAPHY

The optimization of a mobile phase and temperature for RP-HPLC separat ion of 3,5-dinitrobenzoyl derivatives of linear alcohol ethoxylates (L AEs) according to the alkyl chain length is reported. Partial inversio n of the elution order of ethoxymers with a change of acetonitrile con centration is employed. A decrease of the temperature allows a further improvement in homologue separation. The addition of sodium perchlora te reduces the retention of higher ethoxymers. This is used for final separation improvement. The optimal conditions found were: stationary phase: LiChrospher 100 RP-18 endcapped, 5 mu m; column: LiChroCart 250 x 4 mm I.D.; mobile phase: acetonitrile-water (98:2, v/v) with 0.0011 mol/l sodium perchlorate; flow-rate: 1.5 ml/min; temperature: 5 degre es C; detection: UV absorption at 233 nm. These conditions were succes sfully applied to the separation of a mixture of C-12-C-18 LAEs and no nylphenol ethoxylates.