Electromembrane extraction of peptides based on hydrogen bond interactions

Samira Dowlatshah; Frederik André Hansen; Chen Zhou; María Ramos-Payán; Trine Grønhaug Halvorsen; Stig Pedersen-Bjergaard

doi:10.1016/j.aca.2023.341610

Electromembrane extraction of peptides based on hydrogen bond interactions

Anal Chim Acta. 2023 Sep 22:1275:341610. doi: 10.1016/j.aca.2023.341610. Epub 2023 Jul 10.

Authors

Samira Dowlatshah¹, Frederik André Hansen¹, Chen Zhou², María Ramos-Payán³, Trine Grønhaug Halvorsen¹, Stig Pedersen-Bjergaard⁴

Affiliations

¹ Department of Pharmacy, University of Oslo, P.O Box 1068 Blindern, 0316, Oslo, Norway.
² Department of Pharmacy, University of Oslo, P.O Box 1068 Blindern, 0316, Oslo, Norway; West China School of Public Health and West China Fourth Hospital, Sichuan University, Chengdu, 610041, China.
³ Department of Analytical Chemistry, Faculty of Chemistry, University of Seville, c/Prof. García González s/n, 41012, Seville, Spain.
⁴ Department of Pharmacy, University of Oslo, P.O Box 1068 Blindern, 0316, Oslo, Norway; Department of Pharmacy, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, 2100, Copenhagen, Denmark. Electronic address: stigpe@farmasi.uio.no.

PMID: 37524472
DOI: 10.1016/j.aca.2023.341610

Abstract

Background: Electromembrane extraction (EME) of peptides reported in the scientific literature involve transfer of net positively charged peptides from an aqueous sample, through a liquid membrane, and into an aqueous acceptor solution, under the influence of an electrical field. The liquid membrane comprises an organic solvent, containing an ionic carrier. The purpose of the ionic carrier is to facilitate peptide solvation in the organic solvent based on ionic interactions. Unfortunately, ionic carriers increase the conductivity of the liquid membrane; the current in the system increases, the electrolysis in sample and acceptor is accelerated, and the extraction system tend to be unstable and suffers from drifting pH.

Results: In the present work, a broad selection of organic solvents were tested as pure liquid membrane for EME of peptides, without ionic carrier. Several phosphates provided high mass transfer, and tri(pentyl) phosphate was selected since this solvent also provided high operational stability. Among 16 different peptides used as model analytes, tri(pentyl) phosphate extracted those with net charge +1 and with no more than two polar side chains. Tri(pentyl) phosphate served as a very strong hydrogen bond acceptor, while the protonated peptides were hydrogen bond donors. By such, hydrogen bonding served as the primary interactions responsible for mass transfer. Tri(pentyl) phosphate as liquid membrane, could exhaustively extract leu-enkephalin, met-enkephalin, and endomorphin from human blood plasma and detected by LC-MS/MS. Calibration curves were linear (r² > 0.99) within a concentration range from 1 to 500 ng/mL, and a relative standard deviation within 12% was observed for precision studies.

Significance: The current experiments are important because they indicate that small peptides of low polarity may be extracted selectively in EME based on hydrogen bond interactions, in systems not suffering from electrolysis.

Keywords: Electromembrane extraction; Extraction; Peptides; Sample preparation.