SAMPLE PRESERVATION FOR DETERMINATION OF ORGANIC-COMPOUNDS - MICROWAVE VERSUS FREEZE-DRYING

In search of a reliable drying method, which might be used even under field conditions, microwave drying was compared to freeze-drying of pl ant material. Leaves of Ananas comosus and Avicennia germinans as well as buds and phloem of Acer pseudoplatanus were used and checked for o ne or more of the following substances: sugars, sugar alcohols, organi c and amino acids, total nitrogen, and glycinebetaine. With most sampl es good agreement was achieved between the two drying methods. Only in the case of the Ananas comosus leaves, which exhibited low pH and hig h water content, did appreciable differences occur in organic and amin o acids. Besides that, sucrose was the compound most susceptible to al terations, which was especially evident when leaves of Sambucus nigra were dried in the two different compartments (condenser compartment, d rying bell jar) of the freeze-dryer in use. For Ananas comosus leaf sa mples it was shown that microwaving can also be used prior to extracti on of tissue sap.