Parameter optimization for extractions of lipophilic compounds by automated accelerated solvent extraction (ASE)

Optimization of extraction conditions for specific compounds and extractive classes in plant material is performed by means of accelerated solvent extraction (ASE) on a Dionex™ ASE™ 350 instrument.

The search for economically and ecologically feasible sustainable extraction technique for various valuable compounds present in natural materials, often requires optimization of extraction parameters. By varying such parameters as solvent type, solvent polarity, temperature, pressure, particle size and packing density of columns, and extraction time it is possible to achieve optimized yields of target compounds or to tune the selectivity towards special compound classes, observing the requirements of low chemical and energy consumption at the same time.

The ALICE core facility offers optimization of extraction conditions for specific compounds or extractive classes in plant material by means of accelerated solvent extraction (ASE), using the most efficient and flexible Dionex™ ASE™ 350 instrument. A broad variety of solvents applicable in ASE together with possibility to perform extraction under pressure (at elevated temperatures higher than the normal-pressure boiling point of the solvent), allow to reduce solvent viscosity, enhance the permeability of the solid matrix and finally achieve maximum extraction yield. By programmable condition lists, extractions can be optimized with regard to the relevant parameters in a fully automatted way.

Once the most suitable solvent or solvent mixture – as the most important factor – has been established, five important parameters can be further optimized: temperature, static time, purge-time, rinse volume and number of cycles. Sequential extractions can be selected to extract each of a series of samples under a different set of conditions and collect them in separate collection vessels. Samples can also be extracted multiple times to determine extraction completeness. In this way, the optimized extraction conditions for a particular analyte and matrix can be quickly and easily determined.

Up to 24 different containers and collecting vessels can be used for a fast method development. Utilization of several types of extraction cells allow extractions from the milligram to the 10-gram scale. Extraction cells with special coatings arte available if the use special aggressive media should be required.   <

Selective extraction of interesting secondary metabolites can be performed by increasing the polarity of the extraction solvent from highly apolar to highly polar, e.g. from n-heptane over dichloromethane, acetone and ethanol to aqueous media. The following figure displays the extracts of a blueberry sample, extracted consecutively (from left to right) with n-hexane, dichloromethane, ethyl acetate, acetonitrile, and ethanol. (copyright Dionex™, ASE 350® Manual).


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