Utilization of NMR technique to analyze suberin fatty acid mixtures and follow up their reactivity

The European pulp mills produce large amounts of bark as by-product, about 4.3 Mt/y. Additional amounts are produced at sawmills. The cork oak bark is especially rich in suberin, ca 45%. Also birch outer bark contains about 35% of suberin. Suberin - a natural polyester – as a predominant component, is attractive starting material for further modifications and can be used as reactive building block for various polymers, lubricants, paper chemicals and for food and cosmetics ingredients. Suberin can be easily separated and depolymerized leading to corresponding fatty acids, which are mostly straight chain, even numbered C16-C24 hydroxy acids and diacids, with epoxy-, hydroxyl- or olefinic functionalities in the middle of the chain. The dominant suberin monomer is 9.10-epoxy-18-hydroxyoctadecanoic acid. Suberin fatty acids are new potential starting material for various products, the driving force being to replace polymers/materials obtained from non-renewable feedstocks. The development of this chemistry, requires also more effective analytical methods to monitor chemical reactions and to analyze complex product mixtures.1,2,3 In this paper we discuss our recent studies on easy, fast and effective NMR technique to analyze suberin fatty acid mixtures and their derivatives in comparison with typical gas chromatographic – mass spectrometric (GC-MS) method. Our NMR technique proved to be superior especially, because it does not require laborious derivatization with side reactions. In addition different kinds of functional groups and their changes can be easily monitored during the reaction. NMR technique proved to be also quite quantitative compared to GC-MS method.