Which statement best describes when gradient elution should be used relative to isocratic?

Which statement best describes when gradient elution should be used relative to isocratic?

• A. Isocratic is best for a wide range of retention times.
• B. Gradient is never necessary.
• C. Gradient elution is preferred when analytes have widely varying retention times.
• D. Isocratic and gradient have identical performance.

Answer: (C)