What is gradient time and re-equilibration, and why are they important for reproducibility in gradient elution?

What is gradient time and re-equilibration, and why are they important for reproducibility in gradient elution?

• A. Gradient time determines how long the gradient runs; re-equilibration is the time needed to re-establish initial mobile phase composition; important for reproducibility of retention times and peak shapes between runs.
• B. Gradient time is the time between injections; re-equilibration is not required in gradient elution.
• C. Gradient time is how long the column is heated; re-equilibration refers to column washing.
• D. Gradient time and re-equilibration only affect detection, not retention.

Answer: (A)