Determination of salsolinol and related catecholamines through on-line preconcentration and liquid chromatography/atmospheric pressure photoionization mass spectrometry.

A new analytical approach has been developed for simultaneous measurements of endogenous salsolinol and major catecholamines in brain tissue of experimental animals. This procedure involves a combination of on-line phenyl boronate affinity preconcentration and microcolumn liquid chromatography, followed by mass spectrometry equipped with an atmospheric pressure photoionization (APPI) source. Flow conditions of the APPI source were optimized for detection sensitivity while different dopants were evaluated.

Comprehensive assessment of N-glycans derived from a murine monoclonal antibody: a case for multimethodological approach.

Highly efficient separation techniques, laser-induced fluorescence (LIF) detection, and different mass-spectrometric (MS) measurements were combined in a multimethodological scheme to perform a comprehensive structural characterization of N-linked oligosaccharides in a murine monoclonal antibody (immunoglobulin G (IgG(kappa))). Monosaccharide compositional analysis was carried out through a capillary electrophoresis (CE)-LIF method, in which the chemically and enzymatically released sugars were fluorescently labeled. This analysis provides a preliminary assessment of certain structures, being followed by CE-LIF and matrix-assisted laser desorption/ionization (MALDI)-MS profiling of the intact glycan structures.

Enhanced post-source decay and cross-ring fragmentation of oligosaccharides facilitated by conversion to amino derivatives.

Post-source decay (PSD) fragmentation of chemically or enzymatically produced aminoglycans has been evaluated through matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry. Conversion of native glycans to their respective aminoglycan derivatives improved detection sensitivity of the usual fragments and promoted cross-ring fragmentation of linear oligosaccharides, facilitating linkage recognition. The cross-ring fragmentations for both dextrin and dextran oligosaccharides were not limited to the reducing-end glucose moiety, as they were extended throughout the entire molecule.

Determination of electroosmotic flow mobility with a pressure-mediated dual-ion technique for capillary electrophoresis with conductivity detection using organic solvents.

A method is described for the indirect determination of the mobility of the electroosmotic flow (EOF), which can be carried out within a few minutes even for very low mobilities. It is independent of the direction of the EOF. It is based on the comparison of the measured mobilities of two oppositely charged reference ions (tetraphenylphosphonium and tetraphenylborate) with given mobilities in different organic solvents (methanol, acetonitrile, N,N-dimethylformamide, N,N-dimethylacetamide, propylene carbonate) at ionic strengths between 5 and 50 mM.

Separation of carbamazepine and five metabolites, and analysis in human plasma by micellar electrokinetic capillary chromatography.

A rapid and feasible method was developed for the analysis of carbamazepine and its five metabolites (10,11-dihydro-10,11-epoxycarbamazepine, 10,11-dihydro-10,11-dihydroxycarbamazepine, 10,11-dihydro-10-hydroxycarbamazepine, 2-hydroxycarbamazepine and 3-hydroxycarbamazepine) in human plasma. Separation of the analytes is based on micellar electrokinetic chromatography, in untreated fused-silica capillary (48.5/40.

Analysis of dimeric cyanine-nucleic acid dyes by capillary zone electrophoresis in N,N-dimethylacetamide as non-aqueous organic solvent.

A method based on capillary zone electrophoresis is presented for the determination of the purity of commercial dimeric cyanine dyes (TOTO, YOYO, BOBO, all -1 and -3 species, LOLO-1, POPO-1) that are common as fluorescent probes for nucleic acid staining. These dyes are tetracharged cations, and have a strong tendency to interact with negatively charged centres, where they are rapidly adsorbed, especially from aqueous solutions. Thus anionic sites at the capillary wall must be avoided, and aqueous buffers are not suitable.

Electrophoretic mobilities of large organic ions in nonaqueous solvents: determination by capillary electrophoresis in propylene carbonate, N,N-dimethylformamide, N,N,-dimethylacetamide, acetonitrile and methanol.

The mobilities of the monocharged permanent tertraphenylphosphonium cation and tetraphenylborate anion are determined by capillary zone electrophoresis in different organic solvents as a function of the ionic strength, I, of the background electrolyte. The nonaqueous solvents are propylene carbonate (PC), N,N-dimethylformamide (DMF), N,N,-dimethylacetamide (DMA), acetonitrile (MeCN) and methanol (MeOH). The ionic strength is between 5 and 50 mmol/L.

The principle cause for lower plate numbers in capillary zone electrophoresis with most organic solvents.

With longitudinal diffusion as an unavoidable source of peak broadening, the peak efficiency (expressed by the plate number, N) in capillary zone electrophoresis depends on the ratio of electrophoretic mobility, mu, and tracer- or self-diffusion coefficient, D. Both parameters are functions of the ionic strength of the electrolyte solution. According to theory, the mobility is decreased with increasing ionic strength by the relaxation effect (depending on the relative permittivity) and the electrophoretic effect (depending on the relative permittivity and the viscosity of the solvent), whereas the diffusion coefficient is decreased only by the relaxation effect.

Propylene carbonate as a nonaqueous solvent for capillary electrophoresis: mobility and ionization constant of aliphatic amines.

The two properties of aliphatic amines were investigated in propylene carbonate as solvent that are decisive for capillary electrophoretic migration: the actual mobilities and the pKa* values. Solutes were eight primary, secondary, and tertiary amines. Roughly, the actual ionic mobilities of the ammonium ions are inversely proportional to the solvent viscosity, fairly obeying Walden's rule.