Analytical Chemistry: Analytical Separations

____ is a plot of detector response versus retention time.

• Electrophoretogram
• Spectrum
• Elution response
• Chromospectrum
• Chromatogram

An analytical separation technique based on the large differences in solubilities between interferent and analyte.

• Separation by precipitation
• Separation of species by distillation
• Chromatographic separation
• Separation by extraction

Which is true for plate height?

• I The smaller the plate height, the narrower the peaks.
• II The larger the plate height, the better separation between peaks.
• III Plate height can be calculated from the column length, L, and the number of theoretical plates, N.
• IV For fixed number of theoretical plates, N, the longer a solute is on column, the wider the peak will become.

A solute is to be extracted using 150 mL of solvent. Of the options below, which will extract the maximum amount of solute?

• extract with 30 mL five times
• extract with 75 mL twice
• extract with 37.5 mL four times
• extract once with the entire volume
• extract with 50 mL three times

Which form of chromatography is INCORRECTLY defined?

• affinity chromatography – solute binds to a molecule specific for the solute
• adsorption chromatography – solute is adsorbed into solid particles
• ion-exchange chromatography – solute ions of the opposite charge are attracted to the stationary phase
• molecular exclusion chromatography – solute is separated based on size
• partition chromatography – solute equilibrates between the stationary liquid and the mobile phase

A chemical species that causes a systematic error in an analysis by enhancing or attenuating the analytical signal or the background.

• Cation
• Analyte
• Anion
• Interferent

Which of the following is the ratio of length of column packing to retention time?

• Average linear rate of solute migration
• Average linear rate of mobile migration
• Relative migration rate
• Selectivity factor

___ is the physical transfer of solute from one phase to another.

• Miscibility
• Activated transpor
• Partitioning
• Sieving
• Extraction

Which statements are NOT true regarding chromatography?

• I The stationary phase is typically a liquid bonded to the inside surface of a capillary or the surface of solid packed in the column.
• II The mobile phase entering the column is the eluate.
• III Mobile phase is the solvent (gas or liquid) that moves through the column.
• IV Eluent is the process of passing mobile phase though a column.
• V Columns are either open tubular or packed.

It is defined by the relationship σ2 / L where σ2 is the variance obtained from the Gaussian shaped chromatographic peak and L is the length of the column packing in centimeters.

• Plate height
• Retention time
• Column packing length
• Plate count