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Characterization of micelles and liposomes using the Eclipse 3+ AF4 separation system coupled to a DAWN HELEOS II MALS detector
Micelles and liposomes can serve as vehicles used to solubilize and carry bioactive compounds to their site of action, thus increasing their bioavailability. First experience has been made using vitamins and enzymes as functional food additives. Moreover, micelles could be useful to deliver drugs to a defined site of action, thus reducing frequently occurring side effects of systemic drug administration. Micelles are true nano-materials with a size range of 10 to 30 nm in diameter. Ideally, they should have a narrow size distribution. Furthermore, they have to be stable and should release their active compound only in the target region. Characterization of the micelle suspensions is vital to guarantee these properties and has to cover several aspects. One important point is size distribution, which has to be determined with high resolution...
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Asymmetric Flow Field Flow Fractionation (AF4) - A Powerful Method for Polymer Characterization
The AF4-MALS combined technique can serve as a routine method for polymer analysis and characterization. AF4 provides separation efficiency entirely comparable with traditionally used and so far dominating SEC. In addition, it yields superior separation of branched polymers, polymers containing ultra high molar mass fractions up to at least 108 g/mol, and nanoparticles. This contribution outlines the theoretical background of the method and shows several examples of its use, e.g. separation of high molecular weight polymers and particles. While SEC will certainly continue to be the most frequently employed method of polymer analysis, for many samples the description of molecular structure is more detailed if both SEC and AF4 are used. The possibility to run both SEC and AF4 on the same experimental set-up makes the AF4 method a powerful and versatile tool for the characterization of a variety of synthetic and natural polymers and related materials....
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Polyolefins: Determination of Molecular Weight and Branching Structure by GPC/SEC
Polyethylene and Polypropylene are so-called Polyolefins. They are produced in large amounts every year. Depending on the process and catalyst used linear or branched polymers can be produced. In case of e. g. Polyethylene there are at least three polymer types: HDPE (High Density Polytheylene), LDPE (Low Density Polyethylene) and LLDPE (Linear Low Density Polytehylene). HDPE and LLDPE are made of linear or only slightly branched macromolecules with a high level of crystallinity. They form a dense structure in the final product. LDPE is made of highly branched molecules that form a final structure with low density due to a low degree of crystallinity....
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Do you see the complete picture?
"Triple Detection" in Gel Permeation Chromatography
Gel permeation chromatography (GPC) or also named size exclusion chromatography (SEC) is the most often used method for determining the molecular weight of natural and synthetic macromolecules. One specific strength of this method lies in the fact that by the separation process the whole molecular weight distribution is obtained. The molecular weight distribution contains much larger information for the characterization of polymer samples compared to a single value....
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