Gas chromatographic behaviour of C1—C4 aliphatic amides and their N-methyl and N,N-dimethyl derivatives on porous polymers of the porapak type

Aliphatic amides can be analyzed, without any preliminary treatment, by gas chromatography on porous copolymers of the Porapak type. On all of the copolymers studied, amides gave symmetrical chromatographic peaks. The best separation was achieved on Porapak N; all unsubstituted, N-methyl and N,N-dimethylamides of formic, acetic, propionic and butyric acids were separated, except for the pair N- methyl- and N,N-dimethylformamide, which were separated on Porapak Q and T. The sorption of amides on Porapak P, Q, N, R and S and on Synachrom is due mainly to non-specific interactions. Only Porapak T displays appreciable polarity; the order of retention of amides suggests that Porapak T is both an electron donor and, to a lesser extent, an electron acceptro type of adsorbent. The differences in the retentions of amides on Porapak P and Q are in accordance with the difference in the specific surface areas of these sorbents, but the sorption enthalpies are almost identical. The solute—sorbent interaction is of the same nature in both instances, regardless of an order of magnetic difference in the specific surface areas. The excellent sorption properties of Porapaks permitted the reliable determination of the response factors of amides in their detection with flame ionization and thermal conductivity detectors. ..