title: Exhaustive extraction of peptides by electromembrane extraction.
abstract: This fundamental work illustrates for the first time the possibility of exhaustive extraction of peptides using electromembrane extraction (EME) under low system-current conditions (<50 μA). Bradykinin acetate, angiotensin II antipeptide, angiotensin II acetate, neurotensin, angiotensin I trifluoroacetate, and leu-enkephalin were extracted from 600 μL of 25 mM phosphate buffer (pH 3.5), through a supported liquid membrane (SLM) containing di-(2-ethylhexyl)-phosphate (DEHP) dissolved in an organic solvent, and into 600 μL of an acidified aqueous acceptor solution using a thin flat membrane-based EME device. Mass transfer of peptides across the SLM was enhanced by complex formation with the negatively charged DEHP. The composition of the SLM and the extraction voltage were important factors influencing recoveries and current with the EME system. 1-nonanol diluted with 2-decanone (1:1 v/v) containing 15% (v/v) DEHP was selected as a suitable SLM for exhaustive extraction of peptides under low system-current conditions. Interestingly, increasing the SLM volume from 5 to 10 μL was found to be beneficial for stable and efficient EME. The pH of the sample strongly affected the EME process, and pH 3.5 was found to be optimal. The EME efficiency was also dependent on the acceptor solution composition, and the extraction time was found to be an important element for exhaustive extraction. When EME was carried out for 25 min with an extraction voltage of 15 V, the system-current across the SLM was less than 50 μA, and extraction recoveries for the model peptides were in the range of 77-94%, with RSD values less than 10%.
authors.affiliation: School of Pharmacy, University of Oslo, P.O. Box 1068, Blindern, 0316 Oslo, Norway; G&T Septech AS, P.O. Box 33, 1917 Ytre Enebakk, Norway.
authors.forename: Chuixiu
authors.initials: C
authors.lastname: Huang
authors.affiliation: School of Pharmacy, University of Oslo, P.O. Box 1068, Blindern, 0316 Oslo, Norway.
authors.forename: Astrid
authors.initials: A
authors.lastname: Gjelstad
authors.affiliation: School of Pharmacy, University of Oslo, P.O. Box 1068, Blindern, 0316 Oslo, Norway; Department of Pharmacy, Faculty of Health and Medical Sciences, Faculty of Pharmaceutical Sciences, University of Copenhagen, DK-2100 Copenhagen, Denmark. Electronic address: stig.pedersen-bjergaard@farmasi.uio.no.
authors.forename: Stig
authors.initials: S
authors.lastname: Pedersen-Bjergaard
mesh_terms: D005591:Chemical Fractionation / Q000379:methods*; D004560:Electricity; D006863:Hydrogen-Ion Concentration; D008567:Membranes, Artificial; D010455:Peptides / Q000302:isolation & purification*; D013997:Time Factors
chemical_list: D008567:Membranes, Artificial; D010455:Peptides
keywords: Electromembrane extraction (EME); Exhaustive extraction; Low system-current; Peptides; Supported liquid membrane