RepresentativeRamanspectraofthefourchemicalfamiliesof
the corpusarepresentedon Fig. 1. Alltheseorganiccompounds
presentcomparablefunctionalgroups,leadingtosimilaritiesin
their vibrationalsignatures.Specific featurescanhoweverhelp
distinguishing amongthem [10,22,40]. On Fig. 1, abroadRaman
band at3250–3270cm−1 assigned tothestretchingvibrationof
the OHgroups [6] is presentforgluesandgums(Fig. 1a andb),but
absent fromoilsandresins(Fig. 1c–f). Then,aweakbandat