Resistance to Mass Transfer given Van Deemter Equation Calculator

Resistance to Mass Transfer Formula:

\[ C = \frac{H - \frac{B}{u} - A}{u} \]

Plate Height (H):

Longitudinal Diffusion (B):

m²/s

Average Mobile Phase Velocity (u):

m/s

Eddy Diffusion (A):

Resistance to Mass Transfer (C): s

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1. What is Resistance to Mass Transfer in the Van Deemter Equation?

Definition: The resistance to mass transfer (C) represents the contribution to band broadening in chromatography due to the finite rate of mass transfer between the mobile and stationary phases.

Purpose: This calculator helps determine the C term in the Van Deemter equation, which is crucial for understanding and optimizing chromatographic separation efficiency.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ C = \frac{H - \frac{B}{u} - A}{u} \]

Where:

\( C \) — Resistance to mass transfer (seconds)
\( H \) — Plate height (meters)
\( B \) — Longitudinal diffusion coefficient (m²/s)
\( u \) — Average mobile phase velocity (m/s)
\( A \) — Eddy diffusion term (meters)

Explanation: The formula isolates the C term from the Van Deemter equation by subtracting the A and B/u terms from the plate height H, then dividing by the mobile phase velocity.

3. Importance of Resistance to Mass Transfer

Details: Understanding the C term helps chromatographers optimize flow rates and column parameters to minimize band broadening and improve separation efficiency.

4. Using the Calculator

Tips: Enter all parameters in their respective units (H in meters, B in m²/s, u in m/s, A in meters). All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is the Van Deemter equation?
A: The Van Deemter equation describes the relationship between plate height (H) and mobile phase velocity (u) in chromatography: H = A + B/u + Cu.

Q2: Why is resistance to mass transfer important?
A: It becomes the dominant factor in band broadening at higher flow rates, affecting chromatographic resolution.

Q3: What are typical values for the C term?
A: Values typically range from 0.01 to 0.1 seconds, depending on column properties and analytes.

Q4: How can I reduce resistance to mass transfer?
A: Using smaller stationary phase particles, thinner stationary phase films, or optimizing temperature can help reduce C.

Q5: What's the relationship between C and flow rate?
A: The C term becomes more significant at higher flow rates, as mass transfer limitations increase.