Hrc-journal of High Resolution Chromatography, Nov 1, 1985
In this work, an investigation of new organosilicon hydride reagents with phenyl functional group... more In this work, an investigation of new organosilicon hydride reagents with phenyl functional groups for deactivation andsurface modification of fused silica capillary columns is described. Different reagents were tested for their ability to deactivate the fused silica surface, and actual critical surface tension measurements were made using thecapillaryrisemethod.Thedeactivation procedure required lower optimum temperatures than conventional methods. Deactivated capillaries and coated capillary columns were prepared and tested for reproducibility, efficiency, and surface inertness towards basic and acidic compounds at the low nanogram level.
Det finns ett glapp mellan de kunskaper som lars ut pa hogskolorna och de behov som naringslivet... more Det finns ett glapp mellan de kunskaper som lars ut pa hogskolorna och de behov som naringslivet har. Nastan halften av tillvaxtforetagen hittar inte tillrackligt med kandidater nar de ska rekryte ...
In this work, an investigation of new organosilicon hydride reagents with phenyl functional group... more In this work, an investigation of new organosilicon hydride reagents with phenyl functional groups for deactivation andsurface modification of fused silica capillary columns is described. Different reagents were tested for their ability to deactivate the fused silica surface, and actual critical surface tension measurements were made using thecapillaryrisemethod.Thedeactivation procedure required lower optimum temperatures than conventional methods. Deactivated capillaries and coated capillary columns were prepared and tested for reproducibility, efficiency, and surface inertness towards basic and acidic compounds at the low nanogram level.
When optimizing a capillary electrophoresis/electrospray ionization mass spectrometry (CE/ESI-MS)... more When optimizing a capillary electrophoresis/electrospray ionization mass spectrometry (CE/ESI-MS) system, consideration has to be given not only to the separation but also to the electrospray stability. Methods developed for CE/UV analysis of drugs and peptides were considered and modified to be suitable for a CE/MS system with a robust sheathless interface. Different concentrations of the organic modifiers acetonitrile, methanol and 2-propanol were used in the separation buffer. The type and concentrations of these modifiers were also compared with reference to electrospray stability, sensitivity and time of analysis. In addition, different ionic strengths in the buffers were evaluated with reference to electrospray stability. The repeatability was used for the estimation of electrospray stability. The degree to which these parameters influenced the separation and the ESI stability was studied using a nine-peptide standard mixture and the antibiotic drugs bacampicillin and ampicillin as test substances. The analysis time and resolution were used as measures of the efficiency of the separation. A time-of-flight MS analyzer was used since it has the potential advantages of becoming a better fit for integration of CE with MS owing to the speed and sensitivity of this mass analyzer. The detection limit, i.e. 1 µM, for bacampicillin was comparable to what could be achieved with CE/MS on a quadrupole instrument using selected ion monitoring and sheath flow ESI.
Smectlc llquld crystalline polysiloxanes offer unique selectlvltles when used as statlonary phase... more Smectlc llquld crystalline polysiloxanes offer unique selectlvltles when used as statlonary phases In capillary gas chromatography. Retention can be correlated to solute molecular size and shape. I n thls study, blphenylcarboxylate esters, as rnesomorphlc molettes, were coupled via flexible spacers of dlfferent length to a polysiloxane backbone. The resultant phase showed smectlc characteristics from 100 O C to 300 OC, with unsurpassed selectlvlty for the separation of varlous lsomerlc polycycllc aromatic compounds. Important statlonary phase propertles Including efficiency, temperature stablllty, and selectlvlty before and after cross-llnking have been examined for thls new liquld crystalllne phase.
High Flow Extraction Coupled to Capillary LC-MS for Microsomal Metabolic Analysis Using a Positro... more High Flow Extraction Coupled to Capillary LC-MS for Microsomal Metabolic Analysis Using a Positron Emitter for Elucidating Extraction Performance
Sveriges universitet och hogskolor lider av ett ledarskapsproblem. Det ar ett strukturellt proble... more Sveriges universitet och hogskolor lider av ett ledarskapsproblem. Det ar ett strukturellt problem som paverkat verksamheten langt innan den sa kallade Macchiariniskandalen blev ett kant begrepp oc ...
Hybrid capillary-poly(dimethysiloxane)(PDMS) microchips with integrated electrospray ionization (... more Hybrid capillary-poly(dimethysiloxane)(PDMS) microchips with integrated electrospray ionization (ESI) tips were directly fabricated by casting PDMS in a mould. The shapes of the emitter tips were drilled into the mould, which produced highly reproducible three-dimensional tips. Due to the fabrication method of the microfluidic devices, no sealing was necessary and it was possible to produce a perfect channel modified by PolyE-323, an aliphatic polyamine coating agent. A variety of different coating procedures were also evaluated for the outside of the emitter tip. Dusting graphite on a thin unpolymerised PDMS layer followed by polymerisation was proven to be the most suitable procedure. The emitter tips showed excellent electrochemical properties and durabilities. The coating of the emitter was eventually passivated, but not lost, and could be regenerated by electrochemical means. The excellent electrochemical stability was further confirmed in long term electrospray experiments, in...
Hrc-journal of High Resolution Chromatography, Nov 1, 1985
In this work, an investigation of new organosilicon hydride reagents with phenyl functional group... more In this work, an investigation of new organosilicon hydride reagents with phenyl functional groups for deactivation andsurface modification of fused silica capillary columns is described. Different reagents were tested for their ability to deactivate the fused silica surface, and actual critical surface tension measurements were made using thecapillaryrisemethod.Thedeactivation procedure required lower optimum temperatures than conventional methods. Deactivated capillaries and coated capillary columns were prepared and tested for reproducibility, efficiency, and surface inertness towards basic and acidic compounds at the low nanogram level.
Det finns ett glapp mellan de kunskaper som lars ut pa hogskolorna och de behov som naringslivet... more Det finns ett glapp mellan de kunskaper som lars ut pa hogskolorna och de behov som naringslivet har. Nastan halften av tillvaxtforetagen hittar inte tillrackligt med kandidater nar de ska rekryte ...
In this work, an investigation of new organosilicon hydride reagents with phenyl functional group... more In this work, an investigation of new organosilicon hydride reagents with phenyl functional groups for deactivation andsurface modification of fused silica capillary columns is described. Different reagents were tested for their ability to deactivate the fused silica surface, and actual critical surface tension measurements were made using thecapillaryrisemethod.Thedeactivation procedure required lower optimum temperatures than conventional methods. Deactivated capillaries and coated capillary columns were prepared and tested for reproducibility, efficiency, and surface inertness towards basic and acidic compounds at the low nanogram level.
When optimizing a capillary electrophoresis/electrospray ionization mass spectrometry (CE/ESI-MS)... more When optimizing a capillary electrophoresis/electrospray ionization mass spectrometry (CE/ESI-MS) system, consideration has to be given not only to the separation but also to the electrospray stability. Methods developed for CE/UV analysis of drugs and peptides were considered and modified to be suitable for a CE/MS system with a robust sheathless interface. Different concentrations of the organic modifiers acetonitrile, methanol and 2-propanol were used in the separation buffer. The type and concentrations of these modifiers were also compared with reference to electrospray stability, sensitivity and time of analysis. In addition, different ionic strengths in the buffers were evaluated with reference to electrospray stability. The repeatability was used for the estimation of electrospray stability. The degree to which these parameters influenced the separation and the ESI stability was studied using a nine-peptide standard mixture and the antibiotic drugs bacampicillin and ampicillin as test substances. The analysis time and resolution were used as measures of the efficiency of the separation. A time-of-flight MS analyzer was used since it has the potential advantages of becoming a better fit for integration of CE with MS owing to the speed and sensitivity of this mass analyzer. The detection limit, i.e. 1 µM, for bacampicillin was comparable to what could be achieved with CE/MS on a quadrupole instrument using selected ion monitoring and sheath flow ESI.
Smectlc llquld crystalline polysiloxanes offer unique selectlvltles when used as statlonary phase... more Smectlc llquld crystalline polysiloxanes offer unique selectlvltles when used as statlonary phases In capillary gas chromatography. Retention can be correlated to solute molecular size and shape. I n thls study, blphenylcarboxylate esters, as rnesomorphlc molettes, were coupled via flexible spacers of dlfferent length to a polysiloxane backbone. The resultant phase showed smectlc characteristics from 100 O C to 300 OC, with unsurpassed selectlvlty for the separation of varlous lsomerlc polycycllc aromatic compounds. Important statlonary phase propertles Including efficiency, temperature stablllty, and selectlvlty before and after cross-llnking have been examined for thls new liquld crystalllne phase.
High Flow Extraction Coupled to Capillary LC-MS for Microsomal Metabolic Analysis Using a Positro... more High Flow Extraction Coupled to Capillary LC-MS for Microsomal Metabolic Analysis Using a Positron Emitter for Elucidating Extraction Performance
Sveriges universitet och hogskolor lider av ett ledarskapsproblem. Det ar ett strukturellt proble... more Sveriges universitet och hogskolor lider av ett ledarskapsproblem. Det ar ett strukturellt problem som paverkat verksamheten langt innan den sa kallade Macchiariniskandalen blev ett kant begrepp oc ...
Hybrid capillary-poly(dimethysiloxane)(PDMS) microchips with integrated electrospray ionization (... more Hybrid capillary-poly(dimethysiloxane)(PDMS) microchips with integrated electrospray ionization (ESI) tips were directly fabricated by casting PDMS in a mould. The shapes of the emitter tips were drilled into the mould, which produced highly reproducible three-dimensional tips. Due to the fabrication method of the microfluidic devices, no sealing was necessary and it was possible to produce a perfect channel modified by PolyE-323, an aliphatic polyamine coating agent. A variety of different coating procedures were also evaluated for the outside of the emitter tip. Dusting graphite on a thin unpolymerised PDMS layer followed by polymerisation was proven to be the most suitable procedure. The emitter tips showed excellent electrochemical properties and durabilities. The coating of the emitter was eventually passivated, but not lost, and could be regenerated by electrochemical means. The excellent electrochemical stability was further confirmed in long term electrospray experiments, in...
Uploads
Papers by Karin Markides