IDENTIFICATION OF SURFACE ACTIVE AGENTS 789 chromatogram together with the chromatogram of the glyceryl mono- stearate in pyridine provide for an absolute identification of this mate- rial. Glyceryl esters of other fatty a•ids are also readily identifiable by this technique. It is simple to distinguish glyceryl monostearate prepared Figure 5 I0 15 0 Sorbitan monopalmitate (Arlacel 40) after trimethylsilylation RETENTION TIME (Minutes) Figure 6. Sorbitan monostearate (Arlacel 60) after trimethylsilylation from pressed stearic acid and that prepared from hydrogenated tallow fatty acids. Under the conditions of analysis utilized in this study there is no separation of the a- and •-monoglycerides. However, according to a recent publication (16) it is possible to separate these compounds using an ethylene glycol succinate cohlmn. This column has the disadvantage

790 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS RETENTION TIME (Minutes) Figure 7. Sorbitan mono-oleate (Arlacel 80) after trimethylsilylation LAURIC DIETHANOLAMIDE RETENTION TIME (M•nufes) Figure 8. Lauric acid diethanolamide after trimethylsilylation of comparatively low temperature stability, so it cannot be used for analysis of the di-ester components. Figure 2 shows a comparison of the chromatograms of diethylene glycol monostearate before and after trimethylsilylation. One immedi- ately notices the fact that peaks D, E, and F have identical retention

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