title: Capillary and nano-liquid chromatography-tandem mass spectrometry for the quantification of small molecules in microdialysis samples: comparison with microbore dimensions.
abstract: Enhanced sensitivity is a well known benefit of miniaturised LC-electrospray (ESI)-MS/MS methods. The suitability of miniaturised LC-MS/MS for quantification of small molecules in dialysates was investigated using the anti-epileptic drug oxcarbazepine, its active metabolite, 10,11-dihydro-10-hydroxycarbamazepine, and the internal standard for microdialysis probe calibration, 2-methyl-5H-dibenz(b,f)azepine-5-carboxamide, as test compounds. ESI-MS detection is sensitive to matrix effects. Therefore, dialysate matrix effects were investigated by comparing the responses of standards made in water, Ringer's solution (salt solution used as perfusion fluid) and blank dialysate matrix. Due to the occurrence of ion suppression or enhancement, direct injection of dialysis samples onto the analytical column could not be applied for quantification of small molecules in dialysis samples. Column switching was necessary for desalting and preconcentration of the dialysates. However, this approach was not able to completely eliminate salt effects when the injection volume exceeded 1 microL. No differences in response between Ringer's solution and dialysate matrix were detected at capillary and nano-dimensions. Calibration standards should be prepared with Ringer's solution instead of water for quantitative analysis of microdialysates. A microbore, capillary and nano-LC-ESI-MS/MS method were compared in terms of method feasibility, linearity, sensitivity, accuracy and precision. Downscaling to capillary and nano-dimensions resulted in a gain in detection sensitivity of 5 and 50, respectively. Miniaturised LC-MS/MS was found to be fit for quantification of small molecules in dialysates with acceptable accuracy and method precision.
authors.affiliation: Department of Pharmaceutical Chemistry, Drug Analysis and Drug Information, Research Group Experimental Pharmacology, Vrije Universiteit Brussel, Laarbeeklaan 103, 1090 Brussels, Belgium.
authors.forename: Katrien
authors.initials: K
authors.lastname: Lanckmans
authors.forename: Ann
authors.initials: A
authors.lastname: Van Eeckhaut
authors.forename: Sophie
authors.initials: S
authors.lastname: Sarre
authors.forename: Ilse
authors.initials: I
authors.lastname: Smolders
authors.forename: Yvette
authors.initials: Y
authors.lastname: Michotte
mesh_terms: D002138:Calibration; D002220:Carbamazepine / Q000031:analogs & derivatives / Q000032:analysis; D002853:Chromatography, Liquid / Q000295:instrumentation / Q000379:methods*; D015314:Dialysis Solutions / Q000032:analysis / Q000592:standards; D017551:Microdialysis / Q000379:methods; D036103:Nanotechnology / Q000379:methods; D000078330:Oxcarbazepine; D015203:Reproducibility of Results; D021241:Spectrometry, Mass, Electrospray Ionization / Q000295:instrumentation / Q000379:methods*
chemical_list: C039775:10,11-dihydro-10-hydroxycarbamazepine; D015314:Dialysis Solutions; D002220:Carbamazepine; D000078330:Oxcarbazepine