Technology

Electromembrane extraction (EME) was originally inspired by hollow fiber liquid-phase micro­extraction, but with the addition of an electric field.

How does it work?

  • A: Complex sample in a conductive vial
  • B: pH adjusted water in a conductive vial
  • The oil membrane keeps the liquids apart
  • Apply Voltage
  • Charged molecules travels from A to B
  • Vial B is capped and placed in an autosampler

Advantages

  • Non destructive
  • Very clean sample extract (less downtime on your mass spec)
  • Almost 100% recovery
  • Enrichment is possible
Technology Summary

How does Electromembrane Extraction (EME) work?

Two separate compartments holding the sample solution and the acceptor solution, respectively, are separated by an organic solvent immobilized in the pores of a polymeric membrane, called the supported liquid membrane (SLM).

By applying an electric field across the membrane, charged analytes are transported by electrokinetic migration from the sample solution into the acceptor solution, while non-ionic analytes and ions of opposite charge are withheld in the sample solution. The membrane can be in the form of a hollow fiber, as in the initial constructions, or a flat sheet, as in more recent developments. With modern flat sheet membranes, the volume of organic solvent is in the range of 8–10 microliters. The membrane can be about 10 mm wide and 0.1–0.3 mm thick. The organic solvent is often 2-nitrophenyl octyl ether (NPOE) for basic analytes and higher alcohols (hexanol, heptanol) for acidic analytes. Diallyl phthalate and dodecanitrile have also been proposed as alternatives to NPOE.

The transport of ions generates a current, depending on the applied voltage and several other factors, such as pH, added ionic carriers and different membrane solvents. Too high current can result in electrolysis of water, with gas generation and pH changes. Thus, in order to obtain a successful extraction, the current should be kept in the low microampere area. In addition, due to the formation of a boundary layer at the membrane surface, slowing the transportation across the membrane, a shaking mechanism is usually included.

A short and a long answer

Why use Electromembrane Extraction (EME)?

EME provides rapid extraction (3-15 min), efficient sample clean-up and high selectivity for ionizable compounds from blood, other body fluids and environmental samples. Under optimized conditions, EME can provide pure samples for mass spectrometry directly, without need for further separation by using chromatography. The technique will be perfect for automation in clinical laboratories.

There is a real wide range of sample preparation devices and techniques in use in the clinical laboratories today, and quite a few analytical chemists are looking for what the future will bring. They all wonder if they are using the correct technique, or if they should look for a better one.

Then there is the choice; where do I put my money;

  • Sample prep followed by a chromatographic column to save on instrument maintenance costs and downtime of the critical instrument?
  • The sample undergoes minimum sample prep, then diluted (often just diluted) and injected directly on the column. This dramatically reduces lifetime on the column and increases maintenance costs and downtime for the mass spectrometer.

Extracting 100% of you compounds of interest from the most challenging matrixes (biological) is a challenge that should not be taken too easy on. It boils down to two simple questions;

  • Did I get 100% of my analytes from the matrix?
  • If not, can I still use the results, and can these results be basis for ultimately who will live and who will die?

All analytical chemists agree that there is a need for a paradigm shift. And the largest companies in the industry has of course understood the message, and they have already decided to do huge investments in the years to come, to become responsible for this anticipated paradigm shift.

EME has the potential to become responsible for the paradigm shift because the technology provides:

  • A 100% clean extract of the analytes
  • Your sample is not destroyed, you may run it again, and again, and again …
  • You can inject the extract directly in to your high-resolution mass spectrometer. You do not have to use an additional chromatographic separation unless it provides an advantage.

Welcome to the future!

15 min
average drug (narcotics) analysis
1.5 min
average analysis time
Up to
16000 %
analysis efficiency increase