Standardising pyrograms to allow interlaboratory comparison - by determining relative retention temp for n-alkane homologues then applying calibration plot to pyrolysis gases from unknown samples

摘要

Standardisation of pyrograms comprises (1) generating by Curie point pyrolysis of polyethylene, a chromatogram of n-alkane homologues whose retention temps. relative to an internal standard (I) correspond to indices analogous to Kovats indices; and (2) from the resulting instrument-specific calibration relation, inter-laboratory, comparable (i.e instrument-independent) index values are determined for the eluted peaks of the pyrolysis gases of unknown substances, the description of the nonlinear representation of the indices to the standard retention temp. being done by approximation. Pyrolysis is at 600-900 deg. C in presence of added (I) that can be evaporated without decomposition, using a linear temp. programme in the gas chromatograph, and alkanes are monitored with a flame ionisation detector. Pref. pyrolysis is at 700 deg. C and (I) is naphthalene. USE/ADVANTAGE - Pyrogens can be compared between different laboratories and stored in the form of pyrogram data banks. The error involved in the nonlinear representation of indices is less than that caused by the chromatography system.