Use the Van Deemter equation to separate eddy diffusion, longitudinal diffusion, and mass-transfer effects on plate height.
Parameters
Eddy term A
mm
Input Eddy term A.
Longitudinal term B
mm2/s
Input Longitudinal term B.
Mass-transfer term C
s
Input Mass-transfer term C.
Linear velocity u
mm/s
Input Linear velocity u.
Column length L
mm
Input Column length L.
Results
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Plate height H
—
Plate count N
—
Optimal velocity
—
Ratio to optimum
Van Deemter curve
A, B/u, and Cu terms
Velocity-diffusion map
Model and equations
$$H=A+\frac{B}{u}+Cu,\quad N=\frac{L}{H}$$
This simplified model captures the main relationship only. Boundary conditions, losses, nonlinear effects, and code-specific corrections still need separate checks.
How to read it
Use the main plot to read the controlling trend, including break points that a single result card can hide.
Use the sensitivity view to find input combinations where margin collapses quickly.
For early design, focus on which input controls margin before trusting the absolute value.
Learn Chromatography Plate Height Van Deemter by dialogue
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When reading Chromatography Plate Height Van Deemter, where should I look first? Moving Eddy term A changes both the plots and the result cards.
🎓
Start with Plate height H, but do not treat the number as the whole answer. Use Van Deemter curve to confirm the assumed state, then read A, B/u, and Cu terms for the distribution or trend. Use the main plot to read the controlling trend, including break points that a single result card can hide.
🙋
I can see why Eddy term A changes Plate height H. How should I judge the influence of Longitudinal term B?
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Move Longitudinal term B in small steps and watch Plate count N. That reveals which term is controlling the result. This simplified model captures the main relationship only. Boundary conditions, losses, nonlinear effects, and code-specific corrections still need separate checks. A single operating point is not enough; sweep the realistic scatter range.
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What is Velocity-diffusion map for? It feels like the ordinary curve already tells the story.
🎓
Velocity-diffusion map is for finding boundaries where the condition becomes risky or margin collapses quickly. Use the sensitivity view to find input combinations where margin collapses quickly. In First-pass comparison of design options before review, the important question is often what happens after a small change, not only the nominal value.
🙋
So if Plate height H is within the target, can I accept the condition?
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Treat this as a first-pass review. It helps with Narrowing controlling factors and worst-side conditions before detailed analysis and Teaching or explaining the equation, numbers, and visualization under the same inputs, but final decisions still need standards, measured data, detailed analysis, and vendor limits. For early design, focus on which input controls margin before trusting the absolute value.
Practical use
First-pass comparison of design options before review.
Narrowing controlling factors and worst-side conditions before detailed analysis.
Teaching or explaining the equation, numbers, and visualization under the same inputs.
FAQ
Start with Plate height H and Plate count N. Then use Van Deemter curve to confirm the assumed state and A, B/u, and Cu terms to read distribution or bias. Use the main plot to read the controlling trend, including break points that a single result card can hide
Move Eddy term A alone, then move Longitudinal term B by a comparable amount and compare the change in Plate height H. Velocity-diffusion map shows combinations where margin or performance changes quickly.
Use it for First-pass comparison of design options before review. Instead of trusting a single point, widen the input range and check whether Plate height H keeps enough margin before moving to detailed analysis.
This simplified model captures the main relationship only. Boundary conditions, losses, nonlinear effects, and code-specific corrections still need separate checks. Final decisions still require standards, measured data, detailed analysis, and vendor limits.