Basic LC

What is the function of the stationary phase in High Performance Liquid Chromatography (HPLC)?

• To carry the mixture to be separated

• To apply pressure to the mobile phase

• To partition the components of the mixture

• To contain small particles in a steel column

Why is pressure required to push the mobile phase through the stationary phase in HPLC?

• To prevent the mixture from separating

• To enhance the accuracy of identification

• Due to the small particle size of the stationary phase

• To reduce the interaction between the stationary and mobile phases

What is the step that follows the binding of compounds to the stationary phase in the described HPLC process?

• Elution of bound molecules with a suitable buffer

• Interaction of compounds with the mobile phase

• Separation of the stationary phase

• Introduction of more compounds into the analyte

In High-Performance Liquid Chromatography (HPLC), compounds interact with the stationary phase based on specific properties. Which of the following is NOT mentioned as one of these properties?

• Polarity

• Charge

• Molecular weight

• Temperature

Why is degassing performed on mobile phases in liquid chromatography?

• To enhance the flavor of the mobile phase.

• To remove particulate matter from the mobile phase.

• To prevent the formation of gas bubbles in the pump or detector.

• To increase the temperature of the mobile phase.

What is the primary function of the pump in a liquid chromatograph?

• To determine the flow rate in mL/min

• To set the pressure range in psi

• To deliver the mobile phase at a specific flow rate

• To measure the concentration of the mobile phase

Answer explanation

• To determine set the flow rate in mL/min

To set the pressure range in psi mL/min

Degassing is done to prevent formation of gas bubbles in the pump or detector ( Mobile phases are degassed by stirring of the mobile phase under vacuum, sonication or sparing with helium gas)

What distinguishes the two modes of mobile phase delivery by the pump during a chromatographic experiment?

• The type of liquid used in the mobile phase

• The pump's pressure range

• The mobile phase composition

• The flow rate in mL/min

Answer explanation

During the chromatographic experiment, a pump can deliver a constant mobile phase composition (isocratic) or an increasing mobile phase composition (gradient).

Choose the right answer. List 6 types of column for HPLC:

• Guard Column; Fast Column; Preparative; Capillary; Nano; Analytical
• Guard Column; Normal Column; Preparative; Capillary; Nano; Analytical

• Guard Column; Normal Column; Gel-exclusion; Capillary; Nanotechnology; Analytical

• Guard Column; Fast Column; Preparative; Capillary; Nano-capillary; Analytical

What is the primary purpose of the guard columns placed anterior to the separating column in chromatography?

• To enhance the sensitivity of the detector

• To create false peaks in the chromatogram

• To optimize the protective function of the system

• To separate sample components effectively

Answer explanation

Guard column is placed before the separating column serve as protective elements to filter or remove particles and compounds that could disrupt the chromatographic process.

What distinguishes universal detectors from selective detectors in chromatography?

• Universal detectors are more sensitive.

• Universal detectors are more affected by changes in mobile-phase composition.

• Selective detectors are better for measuring bulk properties of the solute.

• Universal detectors have vast applications.