title: Electromembrane extraction from aqueous samples containing polar organic solvents.
abstract: Electromembrane extraction (EME) was performed from aqueous samples and from aqueous samples containing methanol, ethanol, dimethyl sulfoxide, and acetonitrile. The basic drugs pethidine, haloperidol, nortriptyline, methadone and loperamide were used as model analytes. Reversed phase (C18) HPLC with UV (235 nm) and MS detection was used for analysis of the samples. With no organic solvent in the sample, maximum recoveries were obtained after 5-10 min. The maximum recoveries ranged between 83 and 95%. With 50% (v/v) methanol, ethanol, or dimethyl sulfoxide in the sample, recoveries were comparable to those from an aqueous sample, but the time required reaching maximum recovery increased to 15-25 min. With 2-nitrophenyl octyl ether (NPOE) as the supported liquid membrane (SLM), a stable EME system was obtained for 50% (v/v) methanol, 50% (v/v) ethanol, or 75% (v/v) dimethyl sulfoxide in the sample solution. On the other hand, the EME system was unstable with acetonitrile in the sample, as this solvent partly dissolved the SLM. In addition, acetonitrile migrated through the SLM and caused a volume expansion of the acceptor solution. Other SLMs were also tested (ethyl nitrobenzene, isopropyl nitrobenzene, and dodecyl nitrobenzene), but were inferior to NPOE. As a practical example, EME on dried blood spot extracts (80% methanol) were tested, and proved highly successful. These observations showed that EME can be an effective way of preparing aqueous samples containing substantial amounts of an organic solvent.
authors: School of Pharmacy, University of Oslo, P.O. Box 1068, Blindern, 0316 Oslo, Norway.
authors: Knut Fredrik
authors: KF
authors: Seip
authors: Astrid
authors: A
authors: Gjelstad
authors: Stig
authors: S
authors: Pedersen-Bjergaard
mesh_terms: D002851:Chromatography, High Pressure Liquid; D002853:Chromatography, Liquid; D059788:Dried Blood Spot Testing / Q000379:methods; D055664:Electrochemical Techniques / Q000295:instrumentation* / Q000379:methods*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008567:Membranes, Artificial; D000432:Methanol / Q000737:chemistry; D004364:Pharmaceutical Preparations / Q000032:analysis / Q000097:blood / Q000302:isolation & purification*; D015203:Reproducibility of Results; D012997:Solvents / Q000737:chemistry*; D053719:Tandem Mass Spectrometry
chemical_list: D008567:Membranes, Artificial; D004364:Pharmaceutical Preparations; D012997:Solvents; D000432:Methanol
keywords: Basic drugs; Dried blood spots; Electromembrane extraction; Mixed aqueous/organic sample; Supported liquid membrane