1. What is HPLC Gradient Conversion?

HPLC Gradient Conversion is a method used in liquid chromatography to adjust gradient duration when changing flow rates while maintaining the same chromatographic separation. This ensures consistent elution profiles when scaling methods between different instruments or conditions.

2. How Does the Calculator Work?

The calculator uses the HPLC gradient conversion formula:

Where:

• \( \text{New Time} \) — Adjusted gradient duration (min)
• \( \text{Old Time} \) — Original gradient duration (min)
• \( \text{Old Flow} \) — Original flow rate (mL/min)
• \( \text{New Flow} \) — New flow rate (mL/min)

Explanation: The formula maintains constant column volumes by proportionally adjusting gradient time when flow rate changes, preserving separation quality.

3. Importance of Gradient Conversion

Details: Proper gradient conversion is essential for method transfer, scale-up/down processes, and maintaining consistent retention times and peak resolution across different HPLC systems and conditions.

4. Using the Calculator

Tips: Enter original gradient time in minutes, original flow rate in mL/min, and new flow rate in mL/min. All values must be positive numbers greater than zero.

5. Frequently Asked Questions (FAQ)

Q1: Why is gradient conversion necessary?
A: Gradient conversion maintains the same number of column volumes during the gradient, ensuring consistent separation when flow rates change.

Q2: Does this work for all types of HPLC gradients?
A: This formula works for linear gradients. Complex multi-step gradients may require additional calculations for each segment.

Q3: What if I change column dimensions?
A: Column dimension changes require additional scaling factors. This calculator assumes the same column is used with different flow rates.

Q4: Are there limitations to this conversion?
A: The conversion assumes linear solvent strength and may not account for system dwell volume differences between instruments.

Q5: Can this be used for UHPLC methods?
A: Yes, the same principle applies to UHPLC, though additional considerations for pressure limits and system compatibility may be needed.