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Featured researches published by Claes Melander.


Journal of Chromatography A | 2000

Automated liquid membrane extraction for high-performance liquid chromatography of Ropivacaine metabolites in urine

Jan Åke Jönsson; Malin Andersson; Claes Melander; Jan Norberg; Eddie Thordarson; Lennart Mathiasson

An automatic method for the determination of metabolites of Ropivacaine in urine was set up. It utilizes supported liquid membrane extraction for sample clean-up and enrichment, followed by ion-pair chromatography determination using UV detection. The extraction was very selective with no observed interfering compounds from the urine matrix, permitting simple isocratic chromatographic analysis. The detection limits for spiked urine samples were 2-18 nM for the different compounds. The repeatability was 1-3% (RSD) with an internal standard that was also extracted, and about twice without this standard. A throughput of 3.3 samples per hour was achieved and the liquid membrane was stable for more than a week.


Biomacromolecules | 2008

Kinetics of hyaluronan hydrolysis in acidic solution at various pH values.

Kristoffer Tømmeraas; Claes Melander

Hyaluronic acid (HA) was hydrolyzed using varying temperatures (40, 60, and 80 degrees C) and acid concentrations (0.0010, 0.010, 0.10, 0.50, 1.0, and 2.0 M HCl). The degradation process was monitored by determination of weight average molecular weight ( M w) by size-exclusion chromatography with online multiangle laser light scattering, refractive index, and intrinsic viscosity detectors (SEC-MALLS-RI-visc) on samples taken out continuously during the hydrolysis. SEC-MALLS-RI-visc showed that the degradation gave narrow molecular weight distributions with polydispersity indexes ( M w/ M n) of 1.3-1.7. Kinetic plots of 1/ M w versus time gave linear plots showing that acid hydrolysis of HA is a random process and that it follows a first order kinetics. For hydrolysis in HCl at 60 and 80 degrees C, it was shown that the kinetic rate constant ( k h) for the degradation depended linearly on the acid concentration. Further, the dependence of temperature on the hydrolysis in 0.1 M HCl was found to give a linear Arrhenius plot (ln k h vs 1/ T), with an activation energy ( E a) of 137 kJ/mol and Arrhenius constant ( A) of 7.86 x 10 (15) h (-1). (1)H NMR spectroscopy was used to characterize the product of extensive hydrolysis (48 h at 60 degrees C in 0.1 M HCl). No indication of de- N-acetylation of the N-acetyl glucosamine (GlcNAc) units or other byproducts were seen. Additionally, a low molecular weight HA was hydrolyzed in 0.1 M DCl for 4 h at 80 degrees C. It was shown that it was primarily the beta-(1-->4)-linkage between GlcNAc and glucuronic acid (GlcA) that was cleaved during hydrolysis at pH < p K a,GlcA. The dependence of the hydrolysis rate constant was further studied as a function of pH between -0.3 and 5. The degradation was found to be random (linear kinetic plots) over the entire pH range studied. Further, the kinetic rate constant was found to depend linearly on pH in the region -0.3 to 3. Above this pH (around the p K a of HA), the kinetic constant decreased more slowly, probably due to either a change in polymer conformation or due to an increased affinity for protons due to the polymer becoming charged as the GlcA units dissociated.


Journal of Chromatography A | 2004

Liquid chromatography-mass spectrometry analysis of enzyme-hydrolysed carboxymethylcellulose for investigation of enzyme selectivity and substituent pattern

Arieh Cohen; Herje Schagerlöf; Carina Nilsson; Claes Melander; Folke Tjerneld; Lo Gorton


Analytical Chemistry | 2005

Microchip Immobilized Enzyme Reactors for Hydrolysis of Methyl Cellulose

Claes Melander; Dane Momcilovic; Carina Nilsson; Martin Bengtsson; Herje Schagerlöf; Folke Tjerneld; Thomas Laurell; Curt T. Reimann; Lo Gorton


Biomacromolecules | 2006

New approaches to the analysis of enzymatically hydrolyzed methyl cellulose. Part 2. Comparison of various enzyme preparations

Claes Melander; Roland Adden; Gunnar Brinkmalm; Lo Gorton; Petra Mischnick


Biomacromolecules | 2006

New approaches to the analysis of enzymatically hydrolyzed methyl cellulose. Part 1. Investigation of the influence of structural parameters on the extent of degradation

Roland Adden; Claes Melander; Gunnar Brinkmalm; Lo Gorton; Petra Mischnick


Analytica Chimica Acta | 2005

Investigation of micro-immobilised enzyme reactors containing endoglucanases for efficient hydrolysis of cellodextrins and cellulose derivatives

Claes Melander; Martin Bengtsson; Herje Schagerlöf; Folke Tjerneld; Thomas Laurell; Lo Gorton


Starch-starke | 2006

Hydrolysis of Maltoheptaose in Flow through Silicon Wafer Microreactors Containing Immobilised α-Amylase and Glycoamylase

Claes Melander; Wiebke Tüting; Martin Bengtsson; Thomas Laurell; Petra Mischnick; Lo Gorton


Analytical and Bioanalytical Chemistry | 2007

Studies of the separation and characterisation of mixtures of starch and cellulose derivatives by use of chromatography and mass spectrometry

Carina Nilsson; Anna Asplund; Herje Schagerlöf; Claes Melander; Anne Andersen; Folke Tjerneld; Arieh Cohen; Lo Gorton


Macromolecular Symposia | 2009

The Applicability of Enzymes in Cellulose Ether Analysis

Roland Adden; Claes Melander; Gunnar Brinkmalm; Matthias Knarr; Juergen Engelhardt; Petra Mischnick

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Petra Mischnick

Braunschweig University of Technology

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Roland Adden

Braunschweig University of Technology

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Dane Momcilovic

Royal Institute of Technology

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