Lignin-carbohydrate compounds, polarity

Fraction I, which consists mainly of low molar mass compounds, also contains a small amount of high molar mass lignin derivatives eluting with relative retention volumes of 0-0.1. These derivatives are polar and some may be bound to carbohydrates, or otherwise they would have been eluted by RPC along with the hydrophobic fractions II-IV. 

Many unidentified peaks are present in all chromatograms of the various methyl ether and methyl ester fractions. Certain peaks may be attributed to the presence of partially or fully methylated carbohydrates or their derivatives. Based upon predicted retention times, considerations of molecular weight, and polarity of such compounds, and preliminary investigations of model compounds, it seems highly improbable that all of the unidentified compounds are derived from carbohydrates. Hence, identification of other compounds in these chromatograms can be pertinent not only to a more precise description of products formed in the various reactions but also to basic information concerning lignin chemistry. 

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