The effect of glycerol on the rate of movement of some amino acids on silica gel thin layers Difficulties due to the presence of glycerol have been reported1 in the movement of simple sugars on silica gel and cellulose thin layers. Similar difficulties have been experienced in attempting to identify the free amino acids in pollen extracts preserved in 50 o/o glycerolsolution.
Amino acid mixtures have been resolved using thin-layer chromatography (TLC) on layers of acetylated cellulose2, aluminium oxide 3-5, calcium hydroxidee, calcium oxide', calcium phosphateO, calcium sulphate*, cellulose+ll, iron oxide hydratels, kieselguhl4, magnesia', magnesium trisilicate hydratela, polyacrylonitrilel* and polyamide 16 powders, sephadexlO-l7 and silica gel 4s 18--27. Since the latter has found greatest application in TLC of amino acids, silica gel was selected as the adsorbent in preliminary work on the effect of the presence of glycerol on the rate of movement of some amino acids, prior to applying the method to the resolution of the free amino acids in pollen extracts.
Air-dried silica gel layers are recommended although RANDERATEP suggests they may also be dried at an elevated temperature provided they are exposed to air for at least 30 min before use. Activation at ZIOO for 15 min with subsequent exposure to air for periods of 30-60 min resulted in greater variation in XF values than when when air-dried plates were used.