title: On-line isotachophoretic sample focusing for loadability enhancement in capillary electrochromatography-mass spectrometry.
abstract: The use of isotachophoretic (ITP) sample focusing to improve the detection limits for the analysis of charged compounds in capillary electrochromatography (CEC) is described. A coupled-column set-up was used with a 220-microm inner diameter capillary, in which counterflow ITP focusing was performed, connected via a T-junction to a 75-microm inner diameter CEC capillary. As is illustrated, the use of ITP focusing resulted in a dramatic reduction of the sample concentration detection limits. To demonstrate the performance of the ITP-CEC combination, several cationic low-molecular mass compounds in a plasma and urine matrix are analysed using UV-absorbance and mass spectrometric detection. A linear calibration curve was constructed over three decades and detection limits in the low nmol/l range were found for academic samples, using UV-absorbance detection.
authors.affiliation: Division of Analytical Chemistry, Leiden/Amsterdam Center for Drug Research, Leiden University, The Netherlands.
authors.forename: M
authors.initials: M
authors.lastname: Mazereeuw
authors.forename: V
authors.initials: V
authors.lastname: Spikmans
authors.forename: U R
authors.initials: UR
authors.lastname: Tjaden
authors.forename: J
authors.initials: J
authors.lastname: van der Greef
mesh_terms: D020374:Chromatography, Micellar Electrokinetic Capillary / Q000379:methods*; D004586:Electrophoresis / Q000379:methods*; D013058:Mass Spectrometry / Q000379:methods*; D012680:Sensitivity and Specificity; D013056:Spectrophotometry, Ultraviolet