Calculator Inputs
The page layout stays single-column, while the input controls use three columns on large screens, two on medium screens, and one on mobile.
Example Data Table
| Scenario | Reference Method | Transferred Method | Estimated Result |
|---|---|---|---|
| Analytical transfer | 4.6 × 150 mm, 5 µm, 1.00 mL/min | 3.0 × 100 mm, 5 µm, porosity 0.68 | ID-scaled flow ≈ 0.43 mL/min |
| Dead time check | Run time 8 min | Void volume ≈ 0.48 mL | Dead time ≈ 1.13 min |
| Solvent planning | Transferred flow ≈ 0.43 mL/min | 8 minute method | Solvent use ≈ 3.40 mL |
Formula Used
Area = π × (ID / 20)2
ID is entered in millimeters. Dividing by 20 converts radius to centimeters.
Flow = Area × Linear Velocity
Area in cm² and velocity in cm/min produce mL/min directly.
F2 = F1 × (ID2 / ID1)2
This keeps linear velocity similar when only internal diameter changes.
F2 = F1 × (ID2 / ID1)2 × (dp2 / dp1)2 × (L1 / L2)
This estimates a flow that stays near the same pressure envelope as the reference method.
Column Volume = Area × Column Length
Void Volume = Column Volume × Porosity
Dead Time = Void Volume / Flow
Solvent Use = Flow × Run Time
How to Use This Calculator
- Enter a reference method if you are transferring an existing separation.
- Enter the new column diameter, length, and particle size.
- Provide a target linear velocity when you want a direct velocity-based flow estimate.
- Set porosity to match your packing assumptions. A common estimate is 0.68.
- Enter run time to estimate solvent use for each injection.
- Submit the form and review the recommended operating flow shown above the inputs.
- Compare the velocity-based, diameter-scaled, and pressure-adjusted values before finalizing a method.
- Use the CSV or PDF buttons to save your calculation output.
FAQs
1) What flow rate is common for a 4.6 mm analytical column?
Many 4.6 mm analytical columns run near 0.8 to 1.5 mL/min. The exact value depends on column length, particle size, solvent viscosity, temperature, and instrument pressure limits.
2) Why use target linear velocity instead of only copying flow?
Linear velocity better reflects how quickly mobile phase moves through the packed bed. Matching velocity usually gives more comparable retention behavior when the new column diameter changes.
3) Does a smaller particle size always allow higher flow?
No. Smaller particles usually increase backpressure. Even if they improve efficiency, the system may require a lower practical flow to remain inside safe pressure limits.
4) What porosity value should I enter?
A value around 0.68 is a common estimate for packed columns. Use a vendor-specific or experimentally determined value when you need a more accurate dead-time estimate.
5) Is dead time the same as analyte retention time?
No. Dead time is the time required for an unretained compound to pass through the column. Retention time includes additional interaction with the stationary phase.
6) Can this calculator help with UHPLC method transfer?
Yes. It is useful for UHPLC planning, especially when comparing smaller diameters and particles. You still need to confirm your instrument and column pressure ratings.
7) Why can the pressure-adjusted flow be lower than the diameter-scaled flow?
Pressure rises when columns get longer or particles get smaller. The pressure-adjusted estimate accounts for those changes, so it can recommend a safer, lower operating flow.
8) Why is solvent consumption included?
Solvent use affects operating cost, waste generation, sample throughput, and method sustainability. Tracking it helps when optimizing methods for routine laboratory work.