共沸蒸馏法在植物水分和土壤水分提取中的应用

Application of Azeotropic Distillation in the Extraction of Plant Water and Soil Water

通过室内可控条件下的共沸蒸馏实验,采用4种溶剂(苯、甲苯、二甲苯、正己烷)对新鲜蚕豆的叶、茎组织和2种处理(不同含水量)的2种土壤(砂质壤土和粉砂质粘土)的水分分别进行了提取,并采用阿贝折射法对蚕豆叶、茎组织的自由水和束缚水含量进行了测定。实验结果表明,正己烷不能用于蚕豆水分的提取,苯、甲苯和二甲苯则可以有效的提取蚕豆水分,提取的水分占蚕豆样品质量的比例大小均为二甲苯>苯>甲苯,提取相同质量水分消耗溶剂量大小依次为苯、甲苯、二甲苯。二甲苯由于共沸点较高(92℃)破坏了原生质胶体而提取出了部分束缚水。因此,进行植物水分提取应根据实验条件和研究目的来选择提取溶剂;4种溶剂均可用于土壤水分的提取,提取的水分含量和溶剂消耗量的大小顺序与蚕豆提取实验结果一致,其中正己烷提取的水分最少,消耗最多。由于二甲苯的共沸点(92℃)温度对土壤影响可能比蚕豆要小,二甲苯可能是最佳的土壤水分提取溶剂;另外,蚕豆组织、土壤质地性质及含水量对水分提取结果均会产生一定的影响。

An azeotropic distillation experiment was conducted in the laboratory to compare extraction of fresh horsebean （Vicia faba Linn） leaf and stem water and soil water with 4 different solvents （Benzene, toluene, xylene and hexane） respectively. Two soils （Sandy loam soil and silty clay soil） with different treatment （different water content） were used, and free water and bound water in leaf and stem tissue of horsebean were also measured by Abbe Refractometer. The results show that all of the solvents can be used to extract horsebean water except hexane, the ratios of distillation water to horsebean mass is that xylene^benzene^toluene, while solvent dissipation order with same water extraction is benzene, toluene and xylene. Azeotrope boil point of xylene is high （92 ℃） and will destroy protoplasm colloid to release some bound water. Solvents choice should according to experimental condition and research object when a- dopting azeotropic distillation to extract water from plants, All of the 4 solvents are able to distill water from different texture soils with different treatments, and the results of water extraction and solvents dissipation are consistent with the horsebean, and thereinto, hexane extracted least water from soil while consumed most, Maybe xylene is the optimal extraction solvent owing to its azeotropic boil point with water （92 ℃） has less effect on soils than horsebean tissue. In addition, horsebean tissue, soil texture and different water content influence the results of water extraction on some extent.