HPLC Mobile Phase Volume Calculator for a Sequence

Prepare the right amount of mobile phase for a sequence.

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Number of injections

Run time incl. re-equilibration min

Flow mL/min

Gradient start %B %

Gradient end %B %

Gradient time min

Purge, equilibration & flush mL

Safety margin %

Example: 48-injection sequence with a 20 min linear gradient inside a 30 min cycle. Time outside the gradient is assumed at the starting %B.

Mobile phase A–

Mobile phase B–

Sequence time–

B per run = F·(tG·(b₀ + b₁)/2 + (t_run − tG)·b₀)/100 · A per run = F·t_run − B per run

How it works

Running out of mobile phase overnight ruins a sequence, and preparing litres more than you need wastes solvent and buffer that may expire. This planner integrates the gradient over each run to split the volume between A and B, then adds the volume used for purging, equilibration and the final flush.

Aqueous buffers without organic solvent support microbial growth, so most laboratories set a short expiry for them.