Gel-electromembrane extraction of peptides: Determination of five hypothalamic agents in human plasma samples.

Agarose gel as a green membrane has been proposed for use in electromembrane extraction of five hypothalamic-related peptides without an ionic carrier. Octreotide, goserelin, triptorelin, cetrorelix, and somatostatin were extracted from 5.0 mL of sample solution (adjusted to pH 5.0) into a microvolume acceptor solution (HCl, 100 mM) under the applied voltage of 30 V in 15 min. The pH of the agarose gel 3.0% (w/v) was adjusted to 4.0 to facilitate the movement of peptides through the membrane. Quantification was performed using an HPLC-UV system on a C18 column. Quantification and detection limits were found to be in the range of 15.0–20.0 ng mL−1 and 4.5–6.0 ng mL−1, respectively. Dynamic linear ranges were found to be in the range of 15.0–1000 ng mL−1 (R 2 > 0.995) and recoveries were in the range of 62.3–77.6%. The optimized method was applied to spiked human plasma samples. The method showed relative recoveries in the range of 44.8–66.0%. Finally, the proposed method was compared with and shown to have higher recoveries than, the conventional electromembrane extraction method for the peptides under study. Image 1 • An agarose gel was applied as the membrane in EME for relatively high molecular weight peptides. • Aqueous nature of the agarose gel makes it possible to transfer the peptides through the membrane in their ionized form. • The EME of peptides was performed in the absence of any ionic carrier in the membrane. • Recoveries of the peptides was investigated as a function of their net charge. • Higher recoveries compared to the conventional electromembrane extraction was confirmed. [ABSTRACT FROM AUTHOR]