The development of gas-liquid chromatography has made possible the rapid analysis of the volatile substances. In the present study, the technique was utilized for the analysis of carbonyls in the oxidized calamary oil methyl ester.
The chromatographic separations were carried out on Hitachi KGL-2 gas-chromatograph using silicon grease as a stationary liquid phase because of its thermal stability. Plots of the logarithm of the retention time against the number of carbon atom in authentic carbonyls gave straight lines (Fig. 1, 2). Results shown in Fig. 1, 2 clearly indicate that carbonyls whose numbers of carbon are 3-6 and 7-12 can be analyzed at 90°C and 150°C respectively.
Two kinds of samples, ether extract of the steam distillate of the oxidized calamary oil methyl ester and ether extract of the steam distillate treated with 2, 4-dinitrophenylhydrazine solution in which carbonyls were converted to the unvolatile hydrazones were separated at 90°C and 150°C. The elution diagrams illustrated in Fig. 3, 4 demonstrate the successful separation and identification of propanal, butanal, 2-butenal, pentanal hexanal, heptanal, 2-heptenal, 2-octenal, nonanal, and 2, 4-undecadienal (Table 1).
In general the results agreed with those obtained by the combined use of column and paper chromatography except for separation of propanal, which indicated the superior accuracy of gas-chromatography. Unsaturated carbonyls identified by gas-liquid chromatography did not reveal any difference from those by paper and column chromatography, and a principal volatile carbonyl component in the oxidized methyl ester was 2-octenal.