REVERSED-PHASE HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHIC SEPARATION OF 1-NAPHTHYL ISOCYANATE DERIVATIVES OF LINEAR ALCOHOL POLYETHOXYLATES

The optimization procedure for the reversed-phase HPLC separation of 1-naphthyl isocyanate derivatives of linear alcohol polyethoxylates (LAEs) is reported. Using a C-18-bonded silica stationary phase and acetonitrile-water mixtures as mobile phase, different trends in the chromatographic separation of selected 1-tetradecanol polyethyleneglycol ether ethoxymers were observed. In the investigated range of acetonitrile-mobile phase volume ratio (phi), the elution order of the ethoxymers was inverted by increasing the organic solvent content of the mobile phase, and the mobile phase composition was found which provides the co-elution of the tested compounds. On the basis of the trends of capacity factor logarithm (log k') versus the number of ethoxy units (n) at different phi, an increased retention by increasing phi. was also predicted for higher ethoxymers. The separation under the same chromatographic conditions of a C-12-C-18 LAE mixture with an average number of 10 ethoxy units, confirmed the strong variability of LAE chromatographic behaviour in the investigated cp range. The isoeluting conditions found for the C-14 LAE ethoxymers were also applied successfully to the homologue-by-homologue separation of the C-12-C-18 LAE mixture.