Column Packing Size and Shear Effects

For some time the normal column packing particle size available has been around 10 |m but, in common with other forms of liquid chromatography, there has been a trend towards increasing the efficiency by producing smaller particle size packings. However, when working with high molecular weight polymers, the higher linear flow velocity associated with the smaller packing sizes can cause shear degradation of the polymer and the particle size must be selected to suit the molecular weight of the sample polymer. The 10 |im material is appropriate for a very wide range of molecular weights but additional efficiency can be obtained by using 5 |im packing for polymers with moderate molecular weights (ca. 10 000 to 100000) and 3 |im packings can be used for lower molecular weights. For very high molecular weight polymers (ca. > 2 000 000) the use of larger packing size (e.g. 20 |im) should be considered. Where there is potential for shear degradation, lower solution concentrations and lower flow-rates can also reduce this unwanted effect.

Solar Panel Basics

Solar Panel Basics

Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.

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