Claes Melander
Lund University
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Publication
Featured researches published by Claes Melander.
Journal of Chromatography A | 2000
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
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
Arieh Cohen; Herje Schagerlöf; Carina Nilsson; Claes Melander; Folke Tjerneld; Lo Gorton
Analytical Chemistry | 2005
Claes Melander; Dane Momcilovic; Carina Nilsson; Martin Bengtsson; Herje Schagerlöf; Folke Tjerneld; Thomas Laurell; Curt T. Reimann; Lo Gorton
Biomacromolecules | 2006
Claes Melander; Roland Adden; Gunnar Brinkmalm; Lo Gorton; Petra Mischnick
Biomacromolecules | 2006
Roland Adden; Claes Melander; Gunnar Brinkmalm; Lo Gorton; Petra Mischnick
Analytica Chimica Acta | 2005
Claes Melander; Martin Bengtsson; Herje Schagerlöf; Folke Tjerneld; Thomas Laurell; Lo Gorton
Starch-starke | 2006
Claes Melander; Wiebke Tüting; Martin Bengtsson; Thomas Laurell; Petra Mischnick; Lo Gorton
Analytical and Bioanalytical Chemistry | 2007
Carina Nilsson; Anna Asplund; Herje Schagerlöf; Claes Melander; Anne Andersen; Folke Tjerneld; Arieh Cohen; Lo Gorton
Macromolecular Symposia | 2009
Roland Adden; Claes Melander; Gunnar Brinkmalm; Matthias Knarr; Juergen Engelhardt; Petra Mischnick