LWT 39 (2006) 633–646
Phenolic resins for can coatings: I. Phenol-based resole analysed
by GC–MS, GC Â GC, NPLC–GC and SEC
Maurus Biedermann, Koni Grob
Ofﬁcial Food Control Authority of the Canton of Zu
rich, Kantonales Labor Zurich, Fehrenstrasse 15, P.O. Box, CH-8030 Zurich, Switzerland
Received 14 September 2004; received in revised form 6 April 2005; accepted 14 April 2005
Phenolic resins (resoles) are used for curing expoxy and polyester coatings, e.g., for food cans. They consist of oligomeric
materials prepared from phenols (phenol, cresol, tert.-butyl phenol), formaldehyde and butanol and are an analytical challenge
because of the complexity of their composition. A phenol-based resole was selected for a ﬁrst investigation of various analytical
techniques: gas chromatography (GC)–mass spectrometry (MS), comprehensive two-dimensional GC (GC Â GC), normal phase
high-performance liquid chromatography (NPLC, primarily of interest for preseparation for GC analysis), and size exclusion
chromatography (SEC). Mass spectra are discussed for some selected compounds and a list of spectra is added. GC Â GC was the
most powerful method for separating and visualizing the composition of the complex mixture, but the whole battery of methods
might be needed to characterize resoles and to analyse their migration into food or food simulants.
r 2005 Swiss Society of Food Science and Technology. Published by Elsevier Ltd. All rights reserved.
Keywords: Resoles; Phenolic resins; Can coatings; Comprehensive GC Â GC
Ensuring the safety of the migration from can
coatings into food presupposes the compositional
analysis of the migrate, i.e. of the components with a
molecular mass below 1000 Dalton (Da) transferred into
foods or food simulants in amounts exceeding the
threshold of toxicological concern (Kroes et al., 2000).
Compositional analysis or at least characterization is
needed for the toxicological evaluation or to deﬁne for
which mixture a global toxicological assessment has
been performed (Grob, 2001). The migrates from can
coatings are far from being elucidated to the point
enabling to ensure their safety as requested by food
legislation (Grob, Spinner, Brunner, & Etter, 1999).
Most lacquers for can coatings are based on epoxy
resins prepared from bisphenol A diglycidyl ether
(BADGE) and bisphenol A. They are cured (cross-
linked and modiﬁed) by resins of phenolics, trimellitic
acid or amines. The migrate from epoxy resins was
analysed by Biedermann, Grob, Bo
hler, and Widmer
(1998), Berger and Oehme (2000) and Schaefer and
Simat (2004a, b). The migration of trimellitic acid and
the sum of its esters into foods and food simulants was
determined by Fankhauser-Noti and Grob (2004).So
far little is known about the migration of the phenolic
resins, amines and their reaction products formed in the
coatings. This paper describes a ﬁrst part of work
addressing the phenolic resins and their migration.
The chemistry of phenolic resins has been summarized
by Oldring (1996), Burkhart, Oberessl, and Oldring
(1998) and Gardziella, Pilato, and Knop (2000).
Bouajila et al. (2002, 2003a b, c) synthesized resoles,
studied the kinetics of resole formation as well as
the degradation. They used LC–MS as principal
chromatographic tool and studied the fragmentation in
To obtain phenolics, phenol or alkylated phenols,
such as cresols or tert.-butyl phenol (Fig. 1), are reacted
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0023-6438/$30.00 r 2005 Swiss Society of Food Science and Technology. Published by Elsevier Ltd. All rights reserved.
Corresponding author. Tel.: +41 432447131; fax: +41 432447101.
E-mail address: email@example.com (K. Grob).