|
| ||
|
|
||
Chromatography Measurements (chromatography + measurement)
Selected AbstractsRapid Analysis of Glucose, Fructose, Sucrose, and Maltose in Honeys from Different Geographic Regions using Fourier Transform Infrared Spectroscopy and Multivariate AnalysisJOURNAL OF FOOD SCIENCE, Issue 2 2010Jun Wang ABSTRACT:, Quantitative analysis of glucose, fructose, sucrose, and maltose in different geographic origin honey samples in the world using the Fourier transform infrared (FTIR) spectroscopy and chemometrics such as partial least squares (PLS) and principal component regression was studied. The calibration series consisted of 45 standard mixtures, which were made up of glucose, fructose, sucrose, and maltose. There were distinct peak variations of all sugar mixtures in the spectral "fingerprint" region between 1500 and 800 cm,1. The calibration model was successfully validated using 7 synthetic blend sets of sugars. The PLS 2nd-derivative model showed the highest degree of prediction accuracy with a highest,R2 value of 0.999. Along with the canonical variate analysis, the calibration model further validated by high-performance liquid chromatography measurements for commercial honey samples demonstrates that FTIR can qualitatively and quantitatively determine the presence of glucose, fructose, sucrose, and maltose in multiple regional honey samples. [source] Syntheses of cyclic polycarbonates by the direct phosgenation of bisphenol M,JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 6 2005Hans R. Kricheldorf Abstract Bisphenol M was subjected to interfacial polycondensations in an NaOH/CH2Cl2 system with triethylamine as a catalyst. Regardless of the catalyst concentration, similar molecular weights were obtained, and matrix-assisted laser desorption/ionization time-of-flight mass spectra exclusively displayed mass peaks of cycles (detectable up to 15,000 Da). With triethyl benzyl ammonium chloride as a catalyst, linear chains became the main products, but the contents of the cycles and the molecular weights strongly increased with higher catalyst/bisphenol ratios. When the pseudo-high-dilution method was applied, both diphosgene and triphosgene yielded cyclic polycarbonates of low or moderate molecular weights. Size exclusion chromatography measurements, evaluated with the triple-detection method, yielded bimodal mass distribution curves with polydispersities of 5,12. Furthermore, a Mark,Houwink equation was elaborated, and it indicated that the hydrodynamic volume of poly(bisphenol M carbonate) was quite similar to that of poly(bisphenol A carbonate)s with similar concentrations of cyclic species. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1248,1254, 2005 [source] Brain GABA editing by localized in vivo1H magnetic resonance spectroscopyNMR IN BIOMEDICINE, Issue 2 2004G. Bielicki Abstract Editing of GABA by 1H MRS in a specific brain area is a unique tool for in vivo non-invasive investigation of neurotransmission disorders. Selective GABA detection is achieved using sequences based on double quantum coherence (DQC). Our pulse sequence makes accurate measurements without artefacts due to spatial localization. The sequence was tested on a phantom solution. The effect of vigabatrin, a specific inhibitor of GABA transaminase, was measured in rat brain and GABA detection was performed in vivo in monkey brain using this procedure. Rats were spilt into two groups. In the control group, the rats had access to water and, in the other group (vigabatrin, VGB, rats), animals were allowed free access to drinking water containing vigabatrin. After 3 weeks of treatment, rats were anesthetized for in vivo NMR spectroscopy investigation. At the end of the experiment, brains were quickly removed, freeze-clamped and extracted with 4% perchloric acid. One part of the acid extract was used for GABA concentrations assessment by ion exchange chromatography with ninhydrin detection. The second was used for high-resolution NMR analysis. By chromatography measurements, the GABA concentration was 1.23±0.06,,mol/g for controls, while for vigabatrin-treated rats the GABA concentration was 4.89±1.60,,mol/g. The NMR in vivo results were closely correlated with the NMR ex vivo (r=0.99, p<0.01) and chromatography results (r=0.98, p<0.01). The correlation between ex vivo results and chromatography results was also high (r=0.99, p<0.001). This pulse sequence performed GABA editing from a 376,,l voxel located on the right basal ganglia area in a non-human primate brain. This in vivo GABA editing scheme can thus be proposed for accurate measurement of brain GABA concentrations. Copyright © 2004 John Wiley & Sons, Ltd. [source] Enhancing the cell affinity of macroporous poly(L -lactide) cell scaffold by a convenient surface modification methodPOLYMER INTERNATIONAL, Issue 12 2003Jian Yang Abstract In this study, the macroporous poly(L -lactide) (PLLA) cell scaffold was modified for enhancing its cell affinity by an improved surface-treating medium, a mixture of aqueous 0.25 M NaOH/ethanol. Ethanol was applied as a co-treating medium to wet the polylactone and assist the hydroxide nucleophilic attack on the ester bond. Low concentration of NaOH could be applied, severe bulk degradation could be avoided and the residual alkali was easy to remove. Treating time could also be shortened. After treatment under optimal conditions, the surface hydrophilicity and surface energy of PLLA were improved significantly and the surface roughness was also changed. Modification of the spherulite structure on PLLA surface was observed with the treating time using a computer-assisted image analysis system (CAIAS). The results of gel permeation chromatography measurements indicated that only the outer layer of the PLLA was modified and the bulk properties were not altered. Mouse 3T3 fibroblasts culture results indicated that the improved surface-treating medium was effective and convenient for enhancing the cell affinity of PLLA cell scaffold. Copyright © 2003 Society of Chemical Industry [source] | ||||||||||