In vivo investigation of brain and systemic ketobemidone metabolism.

Ketobemidone metabolites have previously been identified in urine and plasma; here we show, for the first time, that norketobemidone and ketobemidone N-oxide are present in in vivo microdialysate from rat brain (striatum) after reverse microdialysis, suggesting striatal metabolism of ketobemidone. Ketobemidone metabolites were also identified in in vivo microdialysate samples from brain and blood, as well as in urine from rats, after subcutaneous administration of ketobemidone. Three Phase I metabolites (norketobemidone, ketobemidone N-oxide and hydroxymethoxyketobemidone) and three Phase II metabolites (glucuronic acid conjugates of ketobemidone, norketobemidone and hydroxymethoxyketobemidone) were identified in the microdialysates after subcutaneous administration.

The effect of sample salt additives on capillary electrophoresis analysis of intact proteins using surface modified capillaries.

The effect of adding alkali salts to protein samples for capillary electrophoretic (CE) analysis of intact proteins was studied. A high degree of peak stacking, even for large proteins, was found to occur when alkali salts were added to the sample. The addition of salt to the protein sample promotes a strong improvement in the peak efficiency of individual proteins giving up to 2.

Restricted-access media development for direct analysis of drugs in biofluids using capillary liquid chromatography.

In analytical sciences the design of novel materials and stationary phases for the sample preparation and separation of analytes from biological fluids is needed. In this work we present different strategies for modification of stationary phases to produce tailored solutions for the analytical problem. In this context a novel shielded polymeric reversed-phase monolithic material was prepared in the presence of different numbers of reactive groups and concentrations of the coating polymer.

Coupling of solid-phase microextraction continuous bed (monolithic) capillaries with capillary zone electrophoresis for direct analysis of drugs in biological fluids.

Hyperlink robust biocompatible solid-phase microextraction (SPME) devices were prepared using continuous bed (monolithic) restricted-access media (RAM) as the SPME capillary insert. The RAM-based SPME approach was able to simultaneously separate proteins from a biological sample, while directly extracting the active components of caffeine, paracetamol and acetylsalicylic acid from the drug NeoCitramonum. The devices were interfaced with a CZE system and fully automated analysis for sample preconcentration, desorption, separation and quantification of analytes was evaluated.

Method development for identification of ketobemidone metabolites in microdialysate samples by coupled-column capillary liquid chromatography-tandem mass spectrometry.

Methodologies for identification of ketobemidone metabolites in microdialysate samples utilizing coupled-column capillary liquid chromatography-electrospray quadrupole time-of-flight tandem mass spectrometry are presented. Two different methods were developed to efficiently analyze the metabolites norketobemidone, ketobemidone N-oxide and hydroxyketobemidone, respectively. Both methods include on-line desalting and trapping of the analytes on micro-solid-phase extraction columns with different retention mechanisms.

Improved properties of the non-covalent coating with N,N-didodecyl-N, N-dimethylammonium bromide for the separation of basic proteins by capillary electrophoresis with acidic buffers in 25 microm capillaries.

Capillaries (25microm I.D.) treated with the double-alkyl-chain cationic surfactant N,N-didodecyl-N, N-dimethylammonium bromide (DDAB) in an improved coating procedure were used for separation of four basic proteins in volatile buffers (ammonium acetate and ammonium hydroxyacetate) as well as in a non-volatile buffer (sodium phosphate) at pH 4.

Influence of ignored and well-known zone distortions on the separation performance of proteins in capillary free zone electrophoresis with special reference to analysis in polyacrylamide-coated fused silica capillaries in various buffers. II. Experimental studies at acidic pH with on-line enrichment.

The separation of acidic and basic model proteins was studied in capillary free zone electrophoresis in a polyacrylamide-coated, electroosmosis-free capillary at pH below their isoelectric points (pI) using various buffers at pH 2.7-4.8 with UV detection at 200 nm.

Influence of ignored and well-known zone distortions on the separation performance of proteins in capillary free zone electrophoresis with special reference to analysis in polyacrylamide-coated fused silica capillaries in various buffers. I. Theoretical studies.

Distortion of the starting zone upon its electrophoretic migration toward the detection window gives rise to both symmetrical zones caused by diffusion, sedimentation in the horizontal section of the capillary and the curvature of the capillary, and asymmetrical zones having their origin in Joule heating, sedimentation in the vertical section of the capillary, pH and conductivity differences between the sample zone and the surrounding buffer, solute adsorption onto the capillary wall, and association-dissociation of complexes between the analyte and a buffer constituent or between analytes. Interestingly and importantly a theoretical study shows that moderate pH and conductivity differences as well as adsorption and all of the above interactions when they are characterized by a fast on/off kinetics do not increase the zone broadening (or only slightly), because the sharpening of one boundary of the zone is about the same as the broadening of the other boundary. In addition the peak symmetry caused by a conductivity difference is in most experiments counteracted by a pH difference.

Microemulsion electrokinetic chromatography of drugs varying in charge and hydrophobicity Part II: Strategies for optimization of separation.

The separation of anionic, cationic, and neutral drugs in microemulsion electrokinetic chromatography (MEEKC) was studied. The concentration of sodium dodecyl sulfate (SDS; surfactant) and 2-propanol (organic solvent) was varied in a three-level full factorial design. 29 different model substances were chosen with different hydrophobicities and charges (neutral, positive, and negative).

Microemulsion electrokinetic chromatography of drugs varying in charge and hydrophobicity: I. Impact of parameters on separation performance evaluated by multiple linear regression models.

The separation of anionic, cationic and neutral drugs in microemulsion electrokinetic chromatography (MEEKC) was studied with a statistical experimental design. The concentration of sodium dodecyl sulfate (SDS, surfactant), 1-butanol (co-surfactant) and borate buffer and the factors Brij 35 (surfactant), 2-propanol (organic solvent) and cassette temperature were varied simultaneously, while the parameters pH (9.2), the concentration of octane (oil, 0.

Non-particulate (continuous bed or monolithic) restricted-access reversed-phase media for sample clean-up and separation by capillary-format liquid chromatography.

Restricted-access reversed-phase non-particulate (continuous bed or monolithic) stationary phases of different hydrophobicity synthesized in 100 microm i.d. fused silica capillaries have been evaluated.

Use of liquid chromatography-diode-array detection and mass spectrometry for rapid product identification in biotechnological synthesis of a hydroxyprogesterone.

In exploratory scale biotechnological process development, the product must be rapidly identified although a reference compound may not always be available. LC-diode-array detection and MS were used for this purpose in a process producing 9alpha-hydroxyprogesterone from progesterone as substrate. The electrospray ionization mass spectrometer was combined with an ion trap mass spectrometer for the second generation MS.

Partial filling-micellar electrokinetic chromatography optimization studies of ibuprofen, codeine and degradation products, and coupling to mass spectrometry: part II.

We describe the use of partial filling-micellar electrokinetic chromatography-mass spectrometry (PF-MEKC-MS) on the pharmaceutical ingredients ibuprofen and codeine phosphate as well as their degradation products and impurities. The study focuses on the change of the borate buffer to the volatile ammonium acetate and the optimization of critical MS parameters. The sensitivity of the method is also evaluated.

A statistical experimental design to study factors affecting enantioseparation of propranolol by capillary electrophoresis with cellobiohydrolase (Cel7A) as chiral selector.

The capillary electrophoretic enantioseparation of rac-propranolol using cellobiohydrolase Tr Cel7A as selector was optimized by an unbiased statistical experimental design. A set of pre-experiments was performed in order to identify critical experimental factors. In the definitive chemometric design pH, ranging from 5 to 7, ionic strength ranging between 0.

Partial filling micellar electrokinetic chromatography optimization studies of ibuprofen, codeine and degradation products, and coupling to mass spectrometry.

Studies have been performed to evaluate whether an on-line partial filling-micellar electrokinetic chromatography (PF-MEKC) system could be applied to a recently developed MEKC method for the separation of ibuprofen, codeine and one of the degradation products. Attempts to couple the PF-MEKC system to MS have also been performed. SDS concentration, micellar zone length and concentration of acetonitrile in the buffer were optimized using factorial design.