Abstract
This Application Note shows the separation of a series of homologous non-ionic surfactants in a technical product with the Agilent 1290 Infinity 2D-LC Solution by combination of a HILIC column in the first dimension and a reversed phase column in the second dimension. Surfactants typically do not show activity in UV detection, hence, the Agilent 1260 Infinity ELSD was used. The visualization of the compounds detected by the ELSD is demonstrated with dedicated 2D-LC software.
Introduction
Fatty alcohol ethoxylates belong to the class of non-ionic surfactants and are used for a large variety of consumer products like cosmetics, cleaners, colors, plant protection, textiles and other industrial applications. The production process starts with a homologous series of fatty alcohol compounds typically from lauryl alcohol (C12) to stearyl alcohol (C18). These compounds are reacted with ethylene oxide, which gives a second homologous series of ethoxylates at the other side of the molecule (Figure 1).
Figure 1. Structure formula of fatty alcohol ethoxylat compounds.To monitor the quality and composition of the technical product, it is important to have a separation method in hand which is able to separate both homologous series, the fatty alcohol component and the successive series of ethoxylate units. The only separation technology which can fulfill this requirement is comprehensive 2-dimensional liquid chromatography by combination of the selectivity of a HILIC and an RP separation. The other challenge is to find the right detection method because UV detection is not possible due to the lack of UV activities of these compounds. Typically an Evaporative Light Scattering Detector (ELSD) is used for such a class of non-UV active and nonvolatile compounds. In addition, this is a cost-effective detection method useful for technical quality control.
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