1. What is Eddy Diffusion in the Van Deemter Equation?

Definition: Eddy diffusion (A) represents the contribution to band broadening from the non-equal paths that solute molecules can take through the packed column.

Purpose: It's one of three terms in the Van Deemter equation that describes the relationship between plate height (H) and mobile phase velocity (u) in chromatography.

2. How Does the Calculator Work?

The calculator uses the Van Deemter equation:

Where:

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

Explanation: The calculator solves for A by subtracting the B/u and C×u terms from the measured plate height (H).

3. Importance of Eddy Diffusion Calculation

Details: Understanding eddy diffusion helps in column design and optimization, as it's a major contributor to band broadening in packed columns.

4. Using the Calculator

Tips: Enter all required parameters (H, B, u, C) with positive values. Mobile phase velocity (u) must be greater than zero.

5. Frequently Asked Questions (FAQ)

Q1: What causes eddy diffusion?
A: It results from different path lengths through the packed column due to irregular packing and particle size distribution.

Q2: How can I minimize eddy diffusion?
A: Use smaller, more uniformly packed particles and ensure proper column packing techniques.

Q3: What's a typical value for eddy diffusion?
A: Typically ranges from 1-10 μm for well-packed columns, but depends on particle size and packing quality.

Q4: Can eddy diffusion be zero?
A: In theory, only in open tubular columns where there's no packing material. In packed columns, it's always present.

Q5: How does eddy diffusion affect resolution?
A: Higher eddy diffusion increases plate height (H), reducing column efficiency and resolution between peaks.