🔄 Gradient Conversion Calculator (Flash/Prep)
Convert a flash chromatography gradient step between time (minutes) and column volumes (CV) for portability between cartridge sizes.
Frequently asked questions
Why do flash systems use column volumes instead of time?
A gradient programmed in column volumes automatically scales to different cartridge sizes at the same flow-rate-to-CV ratio, whereas a time-based program does not — it would elute at a different point in the gradient on a differently sized column. CV-based programming makes methods portable across cartridge sizes.
How do I find my flash cartridge's column volume?
Prepacked flash cartridges usually list their column volume (or silica mass, from which volume can be estimated) on the cartridge label or manufacturer's datasheet. Alternatively, use the Column Volume Calculator if you know the cartridge's internal diameter and length.
Can I use this for a full multi-step gradient, or just one point?
This calculator converts a single time/CV point at a time. For a full gradient program with multiple segments, apply the same conversion factor (F/CV) to each time breakpoint individually.
Accuracy & how this is derived
Derivation: Direct relationship between volume, flow rate and time (V = F × t), expressed in column volume units by dividing by the column's total volume.
Validated against: Standard flash chromatography gradient programming convention used by automated flash purification systems (e.g. Biotage, CombiFlash).
⚠️ For educational and research support only — verify critical results independently before use in regulated, clinical, or publication-bound work.
✔ Last updated: July 2026 · Report an error
Converting flash gradients between time and column volumes
Automated flash chromatography systems typically program gradients in column volumes rather than absolute time, since a CV-based program automatically adapts to different cartridge sizes at the same flow-rate-to-volume ratio, while a time-based program would elute compounds at a different fraction of the gradient if the cartridge size changed. Converting between the two representations lets chemists translate a method developed on one cartridge size to another, or interpret a CV-based gradient program in familiar time units for planning purposes.