| Van Deemter's Equation |
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Information AboutVan Deemter's Equation |
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The Van Deemter equation for plate height is :H = A + B/μ + Cμ Where A, B and C are constants and μ is equal to the flow rate. A is equal to the multiple paths taken by the compound, in open tubular capillaries this term will be zero as there are no multiple paths. The multiple paths occur in packed columns where several routes through the column packing, which results in band spreading. B/μ is equal to the longitudinal diffusion of the particles of the compound. Cμ is equal to the equilibration point. In a column, there is an interaction between the mobile and stationary phases, Cμ accounts for this. The Van Deemter equation can be further expanded to: :H = 2λdp + 2GDm/μ + ω(dp or dc)&2μ/Dm +Rdf&2μ/Ds Where: H is plate height, λ is particle shape (with regard to the packing), dp is particle diameter, G, ω, and R are constants, Dm is the diffusion coefficient of the mobile phase, dc is the capillary diameter, df is the film thickness, and Ds is the diffusion coefficient of the stationary phase. Van Deemter's equation indicates that band broadening mechanisms are proportionally dependent on flow rate, inversely proportional to flow rate and independent of flow rate. EXTERNAL LINKS
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