Supported Liquid Extraction: The Best-Kept Secret in Sample Preparation - - Chromatography Online
Supported Liquid Extraction: The Best-Kept Secret in Sample Preparation


LCGC Europe
Volume 25, Issue 8, pp. 430-436

Supported liquid extraction (SLE) has been around for a long time, but surprisingly it is seldom used to replace classical liquid–liquid extraction (LLE). In SLE, the same aqueous phases used in LLE are coated onto an inert diatomaceous earth support, but instead of shaking the two immiscible phases together, the organic phase is passed through the column (or cartridge) and a very efficient extraction takes place. SLE offers many advantages over LLE, including equivalent or more efficient extraction, no emulsion formation, easy automation, less organic solvent use, less labour and less glassware.

Liquid–liquid extraction (LLE) is probably the most widely used sample preparation process. It has been around for many decades, the theory is fairly easily understood and thousands of publications have demonstrated its usefulness. Most chromatographers are first exposed to the technique in their high school or undergraduate chemistry class. I covered the basics of LLE in a previous "Sample Prep Perspectives" instalment (1), and they will not be repeated here.

There are many advantages to the use and application of LLE. First, the operation is fairly simple and the glassware used is inexpensive. Common solvents are often used for extraction, and most applications involve an aqueous phase and an immiscible organic phase. Initially, the sample can be in either phase, and, depending on the partition coefficients of sample and matrix components in the two phases, compounds of interest often can be quantitatively transferred without the presence of interferences. Adjustments to extraction conditions such as changing pH and ionic strength of the aqueous layer or addition of a second organic solvent to the organic layer are easily made. Recoveries can be quite high and reproducible.

On the other hand, there are also some disadvantages to traditional LLE. First, it involves a great deal of time with laborious shaking that can be user dependent. Vigorous shaking (or even non-vigorous shaking) can result in emulsion formation. Emulsions can be difficult to break, and additional time is usually involved in performing this activity. In its traditional application, the technique consumes large amounts of organic solvents and generates considerable waste. Glassware must be cleaned after each use. Automation is very difficult; the technique is performed serially rather than in parallel so throughput is reduced.


ADVERTISEMENT

blog comments powered by Disqus
LCGC E-mail Newsletters
Global E-newsletters subscribe here:




 

LCGC COLUMNISTS 2014

Column Watch: Ron Majors, established authority on new column technologies, keeps readers up-to-date with new sample preparation trends in all branches of chromatography and reviews developments. LATEST: Avoiding Reversed-Phase Chromatography Problems Through Informed Method Development Practices: Choosing the Stationary-Phase Chemistry


Perspectives in Modern HPLC: Michael W. Dong is a senior scientist in Small Molecule Drug Discovery at Genentech in South San Francisco, California. He is responsible for new technologies, automation, and supporting late-stage research projects in small molecule analytical chemistry and QC of small molecule pharmaceutical sciences. LATEST: Seven Common Faux Pas in Modern HPLC


MS — The Practical Art: Kate Yu brings her expertise in the field of mass spectrometry and hyphenated techniques to the pages of LCGC. In this column she examines the mass spectrometric side of coupled liquid and gas-phase systems. Troubleshooting-style articles provide readers with invaluable advice for getting the most from their mass spectrometers. LATEST: Radical Mass Spectrometry as a New Frontier for Bioanalysis


LC Troubleshooting: LC Troubleshooting sets about making HPLC methods easier to master. By covering the basics of liquid chromatography separations and instrumentation, John Dolan is able to highlight common problems and provide remedies for them. LATEST: Estimating Resolution for Marginally Separated Peaks


More LCGC Columnists>>

LCGC North America Editorial Advisory Board>>

LCGC Europe Editorial Advisory Board>>

LCGC Editorial Team Contacts>>


Source: LCGC Europe,
Click here