No chromophores. Try GC or use LC-MS

 OK, thank you so much, 

Fatty acids have no UV chromophores and therefore not UV detectable.  This is the reason other detectors are used like MS, ELSD, CAD...

Phospholipids rarely have much in the way of UV chromophores until you get down to very short wavelengths. Unfortunately, while hexane is transparent in the low-UV region, silica columns usually require the addition of a more polar solvent to hexane in order to elute phospholipids, and these polar solvents often have a higher UV cutoff. So, the combination of adsorption chromatography and UV detection for phospholipids is not good in terms of phospholipid recovery.