Agilent Gradient Calculator Formula

Agilent Gradient Formula:

\[ \text{Scaled Flow} = \text{Original Flow} \times \left( \frac{\text{New Diameter}}{\text{Old Diameter}} \right)^2 \times \left( \frac{\text{New Length}}{\text{Old Length}} \right) \]

Original Flow (mL/min):

mL/min

New Diameter (mm):

Old Diameter (mm):

New Length (mm):

Old Length (mm):

Scaled Flow:

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1. What is the Agilent Gradient Formula?

The Agilent Gradient Formula calculates scaled flow rates when changing column dimensions in chromatography systems. It helps maintain consistent linear velocity and separation quality when switching between different column sizes.

2. How Does the Calculator Work?

The calculator uses the Agilent gradient formula:

\[ \text{Scaled Flow} = \text{Original Flow} \times \left( \frac{\text{New Diameter}}{\text{Old Diameter}} \right)^2 \times \left( \frac{\text{New Length}}{\text{Old Length}} \right) \]

Where:

\( \text{Original Flow} \) — Original flow rate (mL/min)
\( \text{New Diameter} \) — New column diameter (mm)
\( \text{Old Diameter} \) — Original column diameter (mm)
\( \text{New Length} \) — New column length (mm)
\( \text{Old Length} \) — Original column length (mm)

Explanation: The formula accounts for both cross-sectional area changes (diameter squared) and length changes to maintain consistent linear velocity.

3. Importance of Flow Scaling

Details: Proper flow scaling is essential for maintaining separation efficiency, retention times, and pressure characteristics when changing column dimensions in HPLC and UHPLC systems.

4. Using the Calculator

Tips: Enter all values in the specified units (mL/min for flow, mm for dimensions). All values must be positive numbers greater than zero.

5. Frequently Asked Questions (FAQ)

Q1: Why is the diameter squared in the formula?
A: The cross-sectional area of a column is proportional to the square of the diameter (πr²), so flow must be adjusted by the square of the diameter ratio to maintain linear velocity.

Q2: When should I use this calculation?
A: Use this when transferring methods between columns of different dimensions while wanting to maintain similar chromatographic performance.

Q3: Does this formula account for pressure changes?
A: While it maintains linear velocity, pressure will change significantly with different column dimensions and may require system capability verification.

Q4: Can I use this for different column chemistries?
A: This formula is primarily for dimensional scaling. Different stationary phases may require additional method adjustments.

Q5: What about gradient time scaling?
A: Gradient times should be scaled proportionally to the column volume change, which considers both diameter and length changes.