Preparation and use of a glyceryl triether as an indicator of fat absorption.

I . Tridodecyl glyceryl ether (I ,z,3-tridodecoxypropane) was prepared and purified for use as a lipid-soluble indicator of fat absorption. It was separated from other lipids present in samples of diet, digesta and faeces by thin-layer chromatography and determined by gasliquid chromatography. 2. In balance studies using rats which received a semi-purified diet containing beef tallow, 97-98 "/o of both the dietary tridodccyl glyceryl ether and of thc chromic oxide (Cr,O,) from the diet were recovcrcd unaltered from the faeces. This suggests that both compounds are equally good as digestibility indicators. 3 . When the rats werc killed, analyses of digesta taken from different regions of the gastrointestinal tract showed that, although the Cr,Os passed from the stomach faster than did the fat, the triethcr and fat left the stomach together. This suggested that the triether was more suitable as an indicator of fat absorption in thc digcstive tract than is Cr,O,. 4. Comparisons of the digesta removed from the stomach, jejunum, and ileum of piglets receiving a semi-purified diet containing beef tallow, tridodecyl glyceryl ether, Cr,O, and l4C-labellcd oleic acid also supported the conclusion that the tricther was a suitable indicator of fat absorption from different regions of the digestive tract.