Simultaneous Hydrothermal Decomposition and Derivatizations: Gas Chromatography/Mass Spectrometry for the Characterization of Polyamides

Abstract

A new method which allows a rapid hydrothermal decomposition of polyamides and simultaneous derivatizations, followed by an on-lined Curie-point heating-gas chromatography/mass spectrometry analysis is reported. The reactions were carried out in a sealed glass capillary with an acidic medium of hydrochloric acid (35%owt)/methanol/acetic anhydride 2.5 : 40 : 60, wt) at near-critical pressure and temperature (235°C). About 0.1 mg of polyamides, including diamine-dicarboxylic acid and w-aminoalkanoic acid-types, were decomposed in this acidic medium to diamines, dicarboxylic acids and w-aminoalkanoic acids; the simultaneous methylation of the acids and acetylation of the amines was performed within 5 min in a single step. The characteristic peaks of dimethyl dicarboxylates, methyl dicarboxylates and diacetyl diamines shown in their chromatograms definitely corresponded to the molecular compositions of the polyamides. The influence of the reaction reagent on the chromatograms and the quantitative reproducibility are also described.