# 96-Well Agarose-Gel Electromembrane Extraction

## TL;DR

A new 96-well system using agarose gel membranes for efficient and selective extraction of pharmaceuticals from samples like water and human plasma.

## Contribution

First demonstration of gel electromembrane extraction in a 96-well format using agarose membranes.

## Key findings

- High recovery (40–100%) for compounds with log P < 3.0 using the 96-well agarose-gel EME system.
- The system efficiently removed proteins and phospholipids from human plasma samples.
- Gel-based EME offers better selectivity and greenness compared to traditional oil-based EME.

## Abstract

For the first time, gel electromembrane extraction was demonstrated
in a 96-well system. Gel membranes of 3% w/v agarose and with a thickness
of 3.5 mm were immobilized in hydrophilic polyvinylidene fluoride
(PVDF) filters in a 96-well filter plate. The filters provided mechanical
support for the gel membranes, and were important for the stability
and robustness of the system. A selection of 90 basic pharmaceuticals
in the polarity range −4.2 < log P < 8.1 was used as model analytes (compounds). The compounds were
extracted from 200 μL sample (water or human plasma) adjusted
to pH 4.0 with dilute formic acid, through the gel membrane, and into
200 μL of 100 mM formic acid as acceptor. The extraction potential
was 25 V, and the extraction time was 20 min for careful operation
to limit Joule heating and electroendosmosis. The majority of the
compounds in the polarity range −4.0 < log P < 3.0 were extracted with high recovery (40–100%).
Compounds with log P > 3.0 were discriminated
due to interactions with the gel membrane. Proteins and phospholipids
were not extracted, and the system therefore provided efficient cleanup
from human plasma samples. The 96-well agarose-gel electromembrane
extraction (EME) system showed great potential. Selectivity was controlled
by interactions with the aqueous gel membrane. This is fundamentally
very different from traditional EME with oil membranes, where selectivity
is controlled by electro-assisted partition in and out of the oil
membrane. 96-Well electromembrane extraction with gel membranes of
agarose is favorable in terms of greenness and efficiency for polar
analytes, as compared with systems based on oil membranes.