GC-MS identification of residue compounds from a polyethylene reference material digested with microwave-assisted nitric acid vapor-phase digestion

Abstract

A microwave-assisted nitric acid vapor-phase digestion method was used to digest IRMM CRM VDA-001 polyethylene. The nitric acid digestion residue was dissolved in chloroform and analyzed using GC-MS instrumentation to identify the residual compounds in the chloroform extract with the aid of a mass spectral library. Five major peaks were observed in the chromatogram of the digestion residue. Two of them were pre-identified to be dicarboxylic acids, specifically butanedioic acid and pentanedioic acid. Pure standards were analyzed similarly to the digestion residue by GC-MS. The results of retention times and mass spectra were compared to confirm the identification. Semi-quantitative results for the total residue (identified and unidentified compounds) were obtained through calibration of the GC-MS instrument with butanedioic acid and pentanedioic acid. The amounts of butanedioic acid and pentanedioic acid accounted for 88.6 ± 6.3% of the total residue (N = 2). The digestion efficiency calculated from the total residue amount (sum of identified compounds and unidentified compounds) was 97.5 ± 0.2% (N = 2).