Simultaneous electromembrane extraction of acidic and basic drugs

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In most of the cases, microextraction techniques are applied to isolate and preconcentrate a target compound or a narrow group of them. The simultaneous extraction of a given sample into fractions of analytes with similar chemical characteristics is especially interesting in bioanalysis since biological samples contain plenty of compounds with biological effects that cover a wide range of polarities.

Electromembrane extraction (EME) is an electro-driven technique where the analytes migrate between two aqueous phases, separated by a polymeric membrane where an organic solvent is immobilized in the form of a supported liquid membrane (SLM), due to the application of a voltage gradient at both sides of the SLM. EME, which is characterized by its efficacy and expeditiousness, is usually employed for the isolation of acidic or basic compounds from aqueous samples although some efforts have been developed in order to make possible the simultaneous extraction of both types of analytes (1). Fakhari et al., from the Shahid Beheshti University at Iran, have recently developed an EME approach that allows the simultaneous extraction of a sample and its division into four fractions of analytes with characteristic acid/base properties and polarity (2).

The EME set-up is schematically presented in Figure 1 and consists in two electrodes, each one being divided in two secondary electrodes. The secondary electrodes are introduced in the lumen of the hollow fibers where the acceptor phases are located. The most interesting thing is that each hollow fiber is dipped with a different organic solvent. In this approach, the SLM and the charge of the electrode govern the transference of the analytes from the aqueous sample to the acceptor phases. The extraction takes place as in any conventional EME when a voltage is applied between the two primary electrodes.

Figure 1. EME set-up

Let us look more closely the device and describe in depth each secondary electrode. As it can be observed in Figure 1, there are four secondary electrodes and hollow fibers:
  • Anode 1. The hollow fiber is filled with an aqueous solution of pH 12 while the SLM consists of 1-octanol. These conditions are optimum for the extraction of non polar or moderate polar acidic drugs.
  • Anode 2. The hollow fiber is filled with an aqueous solution of pH 12 while the SLM consists of 1-octanol and a ion pairing agent. These conditions are optimum for the extraction of polar acidic drugs
  • Cathode 1. The hollow fiber is filled with an aqueous solution of pH 1 while the SLM consists of 2-Nitrophenyl octyl ether (NPOE). These conditions are optimum for the extraction of non polar or moderate polar basic drugs.
  • Cathode 2. The hollow fiber is filled with an aqueous solution of pH 1 while the SLM consists of NPOE and ion pairing agents. These conditions are optimum for the extraction of polar basic drugs.

We recommend this article to our readers. The original manuscript presents a deep optimization of the new proposal, where the number of solvents (pure and combined) and the studied analytes are remarkable).

References:
(1) Simultaneous extraction of acidic and basic drugs at neutral sample pH: A novel electro-mediated microextraction approach. Link to the article

(2) An all-in-one electro-membrane extraction: Development of an electro-membrane extraction method for the simultaneous extraction of acidic and basic drugs with a wide range of polarities. Link to the article

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