Chapter 19 Phenolic compounds

Abstract

Publisher Summary This chapter discusses phenolic compounds and the chromatographic techniques used in it. Phenolic compounds are ubiquitous in nature and they perform different functions within the plant or its environment. The single most important development in phenolic analysis of the past decade is the application of high-performance liquid chromatography (HPLC) to their separation and detection. Chromatography of phenolics has developed considerably since the early days when chromatographic separation on filter paper was the main procedure available. The sophistication of modern apparatus, such as HPLC, is considerable, but it can involve large capital expenditures. For quantitative estimation of the less volatile phenolics, such equipment is almost obligatory. For determining estrogenic isoflavone levels in silage or tannin levels in beer, measurement of phenolic content is undoubtedly best achieved by analytical HPLC. By using a pulsed amperometric detector with HPLC, it is possible to measure phenols, such as those which commonly pollute drinking water, down to the levels of ten parts per trillion. A major application of thin-layer chromatography (TLC) to phenolics is to the analytical or preparative separation of the less hydrophilic compounds (methylated flavones, isoflavonoids, and quinonoids) on layers of silica gel. However, water-soluble phenolics are readily separable by TLC, if microcrystalline cellulose or polyamide plates are used. Hence, TLC is a procedure that is applicable to all classes of phenolics without exception.