1 k2Ds

where q is a configuration factor depending on the nature of the stationary phase. In adsorption chromatography the Cs term is expressed in terms of the adsorption/desorption kinetics of the solute molecules on the stationary phase.

van Deemter type plots using different carrier gases show that although nitrogen gives slightly lower H values, this is only achieved at relatively low flow rates ( & 15 cm s_1), and as the flow rate increases the value of H increases rapidly. Hydrogen has a much flatter curve and is best for fast analysis with high flow rates (above 30cms_1). Because of the inherent safety problems from hydrogen, helium is a good compromise and is used in most coupled techniques (e.g. gas chromatography-mass spectro-metry, GC-MS).

A modernized version of the van Deemter equation includes the multipath term (A) in a more generalized term covering mass transfer in the mobile phase (CM):

where:

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.

Get My Free Ebook


Post a comment