title: Clean-up of plasma extracts by gel permeation chromatography during analysis of isosorbide nitrates by capillary gas chromatography.
abstract: This work describes how gel permeation chromatography (GPC) can be used for sample clean-up to reduce the fouling of the column in an automated on-column injector. The analytes were isolated from plasma together with the internal standard (isomannide dinitrate) by liquid-liquid extraction on Extrelut silica columns. The extracts were evaporated and reconstituted in tetrahydrofuran for separation of the analytes from non-volatile plasma components by GPC on a styrene-divinylbenzene column with 100 A pore size. A programmable autosampler with an additional three-way valve was used for injection and fraction collection. The molecular weight fraction between 100 and 700 a.m.u. was collected and transferred to the on-column autosampler for capillary gas chromatography on a 30-m column butt-connected to a 0.2-m pre-column. The pre-column was replaced after 50 sample injections. When the GPC purification was excluded from the work-up procedure a deposit of non-volatile components was formed at the injection zone of the pre-column which resulted in excessive peak-tailing after only five or six injections of plasma extract. The limit of determination was 0.2 ng/ml plasma for isosorbide dinitrate and 0.4 ng/ml for the mononitrates.
authors.affiliation: Kabi Pharma, Solna, Sweden.
authors.forename: P O
authors.initials: PO
authors.lastname: Edlund
authors.forename: K
authors.initials: K
authors.lastname: Johansen
mesh_terms: D001769:Blood; D002849:Chromatography, Gas / Q000379:methods; D002850:Chromatography, Gel; D006801:Humans; D007547:Isosorbide / Q000097:blood*; D015203:Reproducibility of Results; D013056:Spectrophotometry, Ultraviolet
chemical_list: D007547:Isosorbide