HPLC pumps and their types MCQs With Answer

This blog presents targeted MCQs with answers on HPLC pumps and their types specifically for M. Pharm students studying Advanced Instrumental Analysis (MPA 201T). The questions explore pump principles, components, and operation modes such as isocratic and gradient delivery, plus common pump designs like reciprocating piston, dual‑piston and quaternary/binary mixers. Emphasis is placed on performance metrics (accuracy, precision, pulsation, dwell volume), wetted materials, solvent handling, and troubleshooting during method development and validation. Each question is designed to deepen conceptual understanding and practical lab readiness. Answers include concise rationale to help remember critical pump behavior and common troubleshooting tips.

Q1. What is the primary function of an HPLC pump in a chromatographic system?

• To inject sample into the column
• To deliver mobile phase at a precise, controlled flow rate and pressure
• To detect analytes eluting from the column
• To maintain column temperature

Correct Answer: To deliver mobile phase at a precise, controlled flow rate and pressure

Q2. Which statement best describes an isocratic pump operation?

• It changes solvent composition continuously during a run
• It delivers a single, constant solvent composition throughout the run
• It alternates between two fixed flow rates
• It maintains constant pressure while varying temperature

Correct Answer: It delivers a single, constant solvent composition throughout the run

Q3. What distinguishes a binary pump from a quaternary pump?

• A binary pump can handle up to four solvents simultaneously
• A quaternary pump mixes up to four solvents and a binary mixes two solvents
• A binary pump is only used for isocratic work
• Quaternary pumps cannot perform gradients

Correct Answer: A quaternary pump mixes up to four solvents and a binary mixes two solvents

Q4. What is the main function of check valves in a reciprocating HPLC pump?

• To detect leaks in the pump head
• To convert pulsating flow into continuous flow
• To ensure unidirectional flow and prevent backflow during piston strokes
• To filter particulate matter from the solvent

Correct Answer: To ensure unidirectional flow and prevent backflow during piston strokes

Q5. Why is a pulsation dampener used in single‑piston pumps?

• To increase the maximum operating pressure of the pump
• To mix solvents before they reach the column
• To reduce pressure and flow pulsations produced by reciprocating motion
• To remove dissolved gases from solvents

Correct Answer: To reduce pressure and flow pulsations produced by reciprocating motion

Q6. Which principle describes the operation of a dual (two‑piston) reciprocating pump?

• Both pistons move together in phase to double the flow rate
• One piston draws solvent while the other delivers solvent in opposite phases to provide nearly continuous flow
• Pistons operate intermittently and alternate pressure relief
• Pistons are used only for low‑pressure mixing

Correct Answer: One piston draws solvent while the other delivers solvent in opposite phases to provide nearly continuous flow

Q7. Which materials are commonly used for wetted parts in HPLC pumps to ensure chemical compatibility?

• Aluminum and brass
• Stainless steel, PEEK and PTFE
• Polycarbonate and PVC
• Glass and lead

Correct Answer: Stainless steel, PEEK and PTFE

Q8. What is the practical consequence of a large dwell volume in an HPLC pump system when running gradients?

• Sharper peaks and improved resolution
• No effect on gradient timing
• Delay and broadening of the observed gradient response at the column
• Lower backpressure at the column

Correct Answer: Delay and broadening of the observed gradient response at the column

Q9. In constant‑pressure pump operation, what parameter is actively controlled by the instrument?

• Mobile phase composition only
• Pressure is kept constant while flow rate is allowed to vary
• Flow rate is kept constant while pressure varies
• Column temperature is held constant

Correct Answer: Pressure is kept constant while flow rate is allowed to vary

Q10. Which is the principal advantage of using gradient elution with a properly designed gradient pump?

• Eliminates the need for column equilibration
• Improves separation of complex mixtures by changing solvent strength during the run
• Reduces system backpressure below isocratic levels
• Makes detectors unnecessary

Correct Answer: Improves separation of complex mixtures by changing solvent strength during the run

Q11. Which of the following is a common cause of flow instability or leakage in an HPLC pump?

• Worn or damaged pump seals and fittings
• Using high‑purity solvents
• Running at low temperature
• Excessive detector sensitivity

Correct Answer: Worn or damaged pump seals and fittings

Q12. What is a typical analytical HPLC flow rate range achieved by standard pumps?

• 0.01 to 10 mL/min
• 10 to 100 mL/min
• 100 to 1000 mL/min
• 0.0001 to 0.001 mL/min

Correct Answer: 0.01 to 10 mL/min

Q13. How does solvent compressibility affect pump performance in HPLC?

• Compressible solvents increase the accuracy of low flow rates
• High compressibility can cause delayed flow response and increased pulsation
• Compressibility has no effect if check valves are used
• Compressible solvents reduce dwell volume

Correct Answer: High compressibility can cause delayed flow response and increased pulsation

Q14. What is the main purpose of an in‑line degasser placed before the pump?

• To filter out particles >0.2 µm
• To remove dissolved gases and prevent bubble formation in the pump and detector
• To cool the solvent before it enters the pump
• To increase solvent viscosity

Correct Answer: To remove dissolved gases and prevent bubble formation in the pump and detector

Q15. In pump performance terminology, how are “accuracy” and “precision” defined?

• Accuracy is repeatability; precision is closeness to the true flow
• Accuracy is closeness to the set flow; precision is reproducibility of repeated flows
• Both terms mean the same and are interchangeable
• Accuracy refers to pressure, and precision refers to temperature control

Correct Answer: Accuracy is closeness to the set flow; precision is reproducibility of repeated flows

Q16. Which pump type is most suitable for very high pressures encountered in UHPLC?

• Peristaltic pump with large tubing
• Reciprocating piston pump with rigid components and small internal volume
• Gravity‑feed pump
• Syringe pump only designed for infusion

Correct Answer: Reciprocating piston pump with rigid components and small internal volume

Q17. Which component specifically reduces pulsation in single‑piston or intermittent pumps?

• Autosampler
• Pulsation dampener or accumulator
• Column oven
• UV lamp

Correct Answer: Pulsation dampener or accumulator

Q18. What is the definition of “dwell volume” in an HPLC system?

• The void volume of the chromatographic column
• The dead volume between the point of mixing (mixer) and the column inlet
• The total solvent consumption per run
• The volume of the detector flow cell

Correct Answer: The dead volume between the point of mixing (mixer) and the column inlet

Q19. Why is priming an HPLC pump necessary before starting a run?

• To cool the pump motor
• To remove air and ensure the pump head and tubing are filled with solvent
• To calibrate the detector wavelength
• To degrease the column packing

Correct Answer: To remove air and ensure the pump head and tubing are filled with solvent

Q20. Which symptom most likely indicates a malfunctioning check valve in an HPLC pump?

• Stable baseline with consistent retention times
• Erratic flow/pressure readings, spikes or loss of flow during run
• Improved peak symmetry
• Lower solvent consumption

Correct Answer: Erratic flow/pressure readings, spikes or loss of flow during run

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