Separation and characterisation of phenol-formaldehyde (resol) prepolymers using packed-column supercritical fluid chromatography with APCI mass spectrometric detection

Packed-column supercritical fluid chromatography (pSFC), with negative-ion atmospheric-pressure chemical-ionisation (APCI) mass spectrometric (MS) detection has been used to analyse a commercial phenol-formaldehyde (resol) prepolymer. After initial optimisation of the system using a standard dimer species [bis(2-hydroxyphenyl)methane], it was possible to identify positively 34 components in the resin sample, including the starting reagents (phenol and cresol), and a range of dimers, trimers, tetramers and pentamers, with varying phenol/cresol ratios and amounts of methylol substitution. The method requires no pre-separation derivatisation of the resin sample, and a chromatographic run time of ca. 10 min.