Stationary Phases

Several types of conductive materials have been tested for use as packings in electrochemically modulated liquid chromatography. Some of the earlier examples investigated the utility of silver grains, mercury-coated platinum, uncoated graphitic particles, and various organic materials (e.g., conductive polymers) coated on graphitic particles. In general, the stationary phase material must meet the requirements in place for conventional liquid chromatography. These attributes include chemical inertness, high mechanical strength, high surface area, and small uniform size. To be effective as an electrode material, requirements including reasonable electrical conductivity (>0.01 Q-cm) and stability over a wide range of applied voltage must be added to the list of attributes. For packings designed to undergo a formal change in oxidation state through an externally triggered electron-transfer process, the material must also be stable in both its oxidized and reduced forms.

Of the above materials, the greatest degree of success has been achieved to date using uncoated carbonaceous materials such as nonporous glassy carbon and porous graphitic carbon. These materials are stable both chemically (i.e. can be used in strongly acidic and basic mobile phases) and electrochemically (i.e. can be used over a wide range of applied potentials), have a high mechanical strength, and are commercially available as micron-sized particles. The non-porous material, has a lower surface area (~1m2g_1) and therefore a lower separation efficiency, whereas the porous material has a higher surface area (~200m2g~1) and therefore a higher separation efficiency. The coated materials, especially those that undergo a formal change in oxidation state (see below), potentially offer an additional dimension in affecting a separation, but complications regarding stability and reliable coating procedures remain significant issues.

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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