Liquid-Liquid Extraction

Sample preparation is essential for effective chromatographic analysis of lipophilic compounds in complex samples such as serum, urine or food. For this purpose, liquid-liquid extraction with a separation funnel is frequently used to isolate target analytes from other matrix compounds. However, this classical method presents certain disadvantages, such as the formation of emulsions, poor phase separation, and high solvent consumption due to repeated extraction cycles. It is also a personnel-intense technique and cannot be effectively automated.

Column Options

• EXtrelut® NT1 for up to 1 ml of aqueous sample
• EXtrelut® NT3 for up to 3 ml of aqueous sample
• EXtrelut® NT20 for up to 20 ml of aqueous sample

Quantitative Extractions in One Step

Merck’s EXtrelut® NT columns avoid the challenges of liquid-liquid extraction because they replace the separation funnel. In contrast to the traditional technique, the columns enable quantitative extractions to be carried out in one step, thus drastically reducing solvent consumption and extraction time. Furthermore, the eluate need not be dried prior to evaporation. Elution is quick and proceeds independently under hydrostatic pressure. This makes EXtrelut® NT columns also suitable for semi-automated procedures. Liquid-liquid extractions can now be performed more efficiently, more simply and more effectively than ever before.

High-Quality, Chemically-Inert Matrix

EXtrelut® NT columns use a wide-pore, highly pure diatomaceous earth-based solid phase. This kieselguhr matrix is chemically inert and can be used in the pH range of 1-13. Since it is a natural product, the appearance of the sorbent and its water absorption capacity can fluctuate. However, thorough testing of the raw material and stringent control of the final product ensure its high quality remains uniform. Furthermore, the quantity of the sorbent to be used is accurately calculated on the basis of the absorption capacity of the production batch. This guarantees that the indicated sample volume can be adsorbed.

Extraction Parameters

The aqueous sample is applied onto the dry EXtrelut® NT sorbent. It distributes itself in the form of a thin film over the chemically-inert matrix, thus acting as a liquid stationary phase. Subsequently, elution takes place using organic solvents that are non-miscible with water, such as diethyl ether, ethyl acetate or halogenated hydrocarbons. All lipophilic compounds are extracted from the aqueous into the organic phase. During this process, the aqueous phase remains on the stationary phase. The eluate is free from emulsions and can be evaporated without further drying prior to further analysis.

Features and Benefits

• No formation of emulsions
• Saving of solvent, sample and time 
• Simple adaption of classical extraction procedures
• Higher recoveries and cleaner extracts
• Samples are stable when absorbed onto the columns