Exam 26: High-Performance Liquid Chromatography

As particle size decreases for HPLC,the required solvent pressure____________________ ,the plate number____________________ ,and the resolution____________________ ?

A________________________________________is a gradient developed to retain the resolution of a single gradient,but reduces the analysis time.

HPLC operation requires special solvents,HPLC-grade.Additionally,HPLC-grade solvents require pretreatment before use.Which of the following is NOT a characteristic of HPLC-grade solvents or pretreatment required before operation?

The criteria for an adequate separation for isocratic reverse-phase HPLC include which of the following? I The retention factor for all peaks are in the range of 0.5 - 20. II All peaks should be symmetric with an asymmetry factor B/A in the range of 0.9 - 15. III For quantification,the minimum resolution between the two closest peaks should be 1.5,though 2.0 is best to compensate for small changes in separation conditions. IV The pressure must be less than or equal to 15 MPa to prolong instrument life.

Which of the following are characteristics of reverse-phase chromatography? I The stationary phase is polar. II The mobile phase is more polar than the stationary phase. III Less polar mobile phase has a lower eluent strength. IV More polar mobile phase has a higher eluent strength. V The stationary phase is nonpolar.

When deciding between an isocratic elution or a gradient elution,a scouting gradient should be done.Which of the criteria below is INCORRECT?

Which of the following is NOT true for HPLC sample injection.

Elution with a constant composition mobile phase is:

____________________ is the volume between the point at which the solvents are mixed and the beginning of the column.Which is NOT true for dwell volume and dwell time?

The________________________________________creates gradients from up to four solvents by proportioning liquids through a four-way valve before the piston and then pumped into the column.

Normal-phase chromatography uses a____________________ stationary phase and a____________________ mobile phase.The more____________________ the mobile phase becomes,the stronger the eluent strength.

What particle diameter is needed to give 15 000 plates over a 10-cm HPLC column?

Gradient elution is used in HPLC.How is the gradient created for a reverse-phase HPLC experiment?

Which statement(s)is(are)NOT true for partition and adsorption chromatography? I For adsorption chromatography - the lower the eluent strength of the solvent,the more easily it displaces the solute. II For partition chromatography - the more time the solute spends in the mobile phase,the easier it is to elute. III For partition chromatography - solute equilibrates between the mobile phase and the liquid phase bonded to the solid support. IV For adsorption chromatography - solvent molecules compete with solute molecules for binding sites on the stationary phase.

The________________________________________is a sensitive,almost universal detector that responds to all nonvolatile compounds,regardless of their structure.

During method optimization,the relative retention is adjusted by altering all of the following,except:

The________________________________________responds to analytes that are significantly less volatile than the mobile phase.

Which of the following is NOT a detector used with HPLC?

The pressure required to push solvent through the column is dependent on several variables such as column length,particle diameter,etc.For column pressure,which relationship is INCORRECT?

What is the plate height for a 10.0-cm HPLC column packed with 3.5 m solid phase?