The chromatographic behaviour of 38 peptides on layers of s&nixed silica gel alone and impregnated with anionic and cationic detergents has been investigated. On the basis of ffie comparison with the ammo acid constituents, it has been possible to predict the sequence of the affinities of the peptides with the different solvents. Many separations have been carried out on layers impregnated with 4% dodecylbenzenesulphonic acid sohrtion.
INTECODUCMON
With reversed-phase chromatography on thin layers of sila&ed silica gel impregnated with detergents (soap TLC), it has been possible to perform many separations of amino acids that can be effected only with dig&uIty or not at all on ionexchange thin layers'_ The type and concentration of the detergent on the s&nixed silica gel determines the separations that can be achieved. The retention of ammo acids seems to be controlled by their interactions with both the hydrophobic sidechain and the factional group (ion-exchange) of the detergent.
In this work we investigated whether soap TLC can also be used for the separation of peptides. Interesting resuhs have recently been achieved with reversedphase chromatography on C&onded silica coIum& and on pBondapak alkyIpheny1 cohnnns in the presence of ion-pairing reagents in the eluene. EXPERSMENTAL The compounds were dissolved in water-methanol (1 :I). The amount of substance deposited on the Layer was between 1 and 2 pg. The peptides were detected by spraying the wet layers with a solution of 1% ninhydrin in pyridin*glacid acetic acid (5:l) and then heating the Layers at RIOY! for 5 min. The layers (thickness 300 pm) were prepared with a Chemetron automatic apparatus by mixing 20 g of s&mired silica ge! 60 HF (Q (Merck+ Darmstadt, G.F.R.) in 50 ml of 95% ethanol with a knonm concentration of detergent. The detergent concentratiors reported in the text refer to the alcoholic solution in which