Abstract
A quantitative determination of surface-active components in Nekal-type surfactants of isopropyl style was carried out by HPLC. Surface-active substances separated from products prepared by Lederer's method and commercial products were converted quantitatively to methyl esters, and the following 17 components were subsequently separated from these esters by silica gel column chromatography. Their structures were determined by MS and NMR spectrometry as 5 triisopropyl-, 7 diisopropyl-, and 5 monoisopropyl-derivatives. Each component present in the mixtures was determined quantitatively by HPLC (Zorbax SIL, φ 4.6×250mm) using two eluents, such as CHCl3-C6H14 (60/40, vol/vol) [Solvent system I] and CHCl3-C6H14-i-PrOH (4.8/95/0.2, vol/vol/vol) [Solvent system II].
In these determinations, it was necessary to use calibration factors for each component, to make correction for defferences in molar absorption coefficients at the detecting wave length (294nm) and methyl 5, 8-diisopropyl-2-naphthalenesulfonate was used as the internal standard.
The components and their compositions were found to vary according to the reaction condition. The commercial products were classified as two types, on the basis of composition.
