I made a TLC of non-polar fractions from a hexane extract. I used a mixture of hexane-chloroform at different gradients as mobile phase and UV, Iodine and CoCl2 for analize the stains, but I could not spot the alkanes. The fraction looks very pure, as an amorphous powder.
Please search in the Camag CBS data base below, you will find many publications on TLC analysis of alkanes, good luck!
http://www.camag.com/en/tlc_hptlc/customer_magazine_cbs/ccbs_database.cfm
you can try with "CAN" or Phosphomolybdic Acid . I've revealed some alkanes and work very good
Hi Mario! If you are using TLC to identify/detect alkanes, be sure the alkanes you are dealing with have boiling points of 100 oC and over - if I can remember correctly. Other wise they get evaporated off through the process and they'll be nothing left on TLC plate for detection. If that is the case, you'll have to use other detection method.
Take the plate from the developing tank (you are using normal phase SiO2 and a highly volatile solvent, I presume), let it dry w/o heat until the surface become opaque (about 3 minutes) and then put it in an Iodine atmosphere (a TLC developing tank with a tight-fitting lid and iodine crystals strewn across the bottom). Since iodine vapors are lipophilic, they will "dissolve" in the alkanes at the respective spots, rendering them brown against a white background.
Even easier, but less sensitive is spraying the air-dry plate with water mist: the plate becomes translucent, while the spots with the water-repellent alkanes stay white: you will see them as white spots against a gray background.
Good luck!