Step-wise Separation Of Plant Constituents And The Effects On Sorption Of Phenanthrene

The effect of the polarity of the organic solvents on extraction of lipidsfrom plants was studied.(Ⅰ) Hexane, a nonpolar organic solvent, and (Ⅱ)the polar organic solvents mixed with chloroform and methanol (2:1), wereused to extract lipids by Soxhlet extractor from green pepper and leaflettuce. The extracted lipids and the degreased plants compared with theoriginal plant dry samples were used to sorb phenanthrene. The resultsshowed that two solvents exhibited the discrepancy in extracted content oflipids, method (Ⅰ) obtained1.9±0.1%and5.0±0.4%lipids from greenpepper and leaf lettuce, respectively, while method (Ⅱ) acquire to2.6±0.2%and9.5±0.5%lipids, respectively. However, it showed that nosignificant difference (P＞0.05) in the contribution of lipid fractions to theoverall phenanthrene sorption. The contribution was approximately20%for green pepper and60%for leaf lettuce, respectively. Using hexanecould avoid the precipitation of polar compounds and then helped to separate the lipids and degreased plants. The degreased plants may not beregarded as the carbohydrate fractions of the plants, because that thecontributions of degreased plants to the overall phenanthrene sorption wereapproximately80%for green pepper and40%for leaf lettuce.The methods saponification and acidification were widely used tofurther separate fractions from the degreased plant cuticle. Uesd degreasedgreen pepper cuticle as subject, the effect of saponification andacidification on chemical properties and phenanthrene sorption capacity ofdegreased green pepper cuticle was determined, with the cellulose, one ofthe major component in plant cuticle, as comparison. The result showedthat the sorption capacity of both the degreased green pepper cuticle andcellulose was decreased after saponification, and increased afteracidification. Further analysis showed that the chemical properties of thecellulose were changed after saponification. Further more cellulose cannotbe hydrolysised completely by acidification. Therefore the methodsaponification and acidification were ineffective to separate the plant cuticlefractions. We suggest that the theoretical sorption coefficients obtain bypartition-limited model is unreasonable to predict plant accumulation oforganic contaminants.