Wood contains a wide variety of components that are extractable with vari­ous organic solvents or water. Non-polar and semi-polar solvents (hexane, dichloromethane, diethyl ether, MTBE etc.) extract lipophilic oleoresin and fat components, while polar solvents (acetone, ethanol, water, etc.) extract hydrophilic phenolics, sugars, starch and inorganic salts. Acetone and ethanol extract also lipophilic extractives.

A classification of wood extractives is given in Figure 21, while the an­alytical procedure for extractives is outlined in Figure 22. Group analysis

of fatty acids, resin acids, triglycerides, lignans and sterols can be done us­ing a short column GC (5-7 m/0.53 mm capillary column with 0.15 pm film thickness), or by HP-SEC (Figure 23) as well as thin layer chromatography.

The analysis of individual compounds can be done by GC on a longer column (20-30 m/0.20-0.32 mm capillary columns) and reverse phase HPLC, while the identification of compounds can be performed by GC — MS, LC-MS, and NMR of isolated substrates. In case of a poor separation between compounds, the following parameters could be modified: tem­perature gradient, column polarity, type of derivative used in derivatiza — tion. As seen in Figure 24 a better separation, for example, between abietic acid and tri-unsaturated C20 fatty acid, is achieved with somewhat higher ramping. The HP-1 column usually follows a boiling point order, however,

columns with different polarity could also be used (Figure 25) to allow better separation.

As previously mentioned, derivatization of fatty and resin acids is needed for accurate quantitative analysis. Although methylation is a com­monly used method, silylation can sometimes afford better separation (Figure 26). In addition, for some GC columns peak-tailing is more severe for methyl esters than for silyl esters.