GAS CHROMATOGRAPHIC ANALYSIS OF ARTIFACT AMINO ACIDS IN SILK AND WOOL TREATED WITH ALKYLENE OXIDES

Silk and wool fibers were treated with propylene oxide (PO) or 1, 2-butylene oxide (BO) in the presence of aqueous neutral salt such as Na2S2O3 and KSCN according to Shiozaki and Tanaka, and the gas chromatography (GC) of the hydrolysates of the treated silk and wool fibers was studied for the identification and quantitative analysis of the artifact amino acids produced by the treatments with PO and BO. The GC analysis was carried out by the linear temperature-programmed method on OV-17 and Dexsil 300 GC columns after the amino acids in the hydrolysate being converted to n-butyl esters of N-trifluoroacetyl (BTFA) derivatives by the method of Gehrke et al.The peaks of O-2-hydroxypropyltyrosine (PO-TYR) and O-2-hydroxybutyltyrosine (BO-TYR) were observed in the chromatograms of the silk samples treated with PO and BO, respectively, and the peaks found in addition to the corresponding modified tyrosine in the chromatograms of the wool samples treated with PO and BO were considered to be those of N-2-hydroxypropyllysine (PO-LYS) and N-2-hydroxybutyllysine (BO-LYS) respectively. The hydrolysates of silk and wool fibers treated with PO and BO were studied also by the ionexchange liquid chromatography (LC) with an automatic amino acid analyzer under normal conditions. It was found that PO-TYR coeluted with phenylalanine and that no modified lysine peak was identified in the chromatograms of the wool samples.The Kovats retention indices and ΔI values of the BTFA derivatives of the artifact amino acids and of serine and threonine were determined and their correlation with the structure of the amino acid was discussed. The ΔI. values of PO-TYR and BO-TYR were equal to each other and as high as that of phenylalanine.The relative molar responses of the artifact amino acids on a hydrogen flame ionization detector were calculated from the sum of effective carbon numbers of the structural units and used to estimate the contents of the artifact amino acids in the hydrolysates of the PO- and BO-treated silk and wool fibers by GC. The amount of PO-TYR thus obtained was lower by 18% than that estimated by LC in which the ninhydrin color yield of PO-TYR was assumed to be equal to that of phenylalanine.