Chapter 32: Miscellaneous Separation Methods

Question 1

are an important class of solvents that have unique solvating properties. Such fluids have proven quite useful in chromatography and solvent extraction.

Answer 1

supercritical fluid

Question 2

In what chromatographic technique does the supercritical fluid act as the mobile phase?

Answer 2

supercritical fluid chromatography

Question 3

was considered as a hybrid of gas and liquid
chromatography, but now it is thought of as being more similar to HPLC in its operation and instrumentation

Answer 3

SFC

Question 4

is formed whenever a substance is heated above its critical temperature

Answer 4

supercritical fluid

Question 5

is the temperature above which a substance
cannot be liquified.

Answer 5

critical temperature

Question 6

Above the _____________, a substance can no longer be condensed to a liquid by simply applying pressure

Answer 6

critical temperature

Question 7

are capable of dissolving large nonvolatile
molecules.

Answer 7

supercritical fluids

Question 8

has been called a green alternative to HPLC.

Answer 8

SFC

Question 9

TRUE or FALSE
Instruments for supercritical fluid chromatography are similar in design to high-performance liquid chromatographs except that in SFC the pumping system must
include a chilled pump head to keep the fluid in the liquid state and that there
must be provision for controlling and measuring the column pressure

Answer 9

TRUE

Question 10

TRUE or FALSE
The density of a supercritical fluid increases rapidly and nonlinearly with pressure increases

Answer 10

TRUE

Question 11

TRUE or FALSE
Density increases also change retention factors (k) and thus elution times

Answer 11

TRUE

Question 12

TRUE or FALSE
The most uncommon pressure profiles
used in SFC are often constant (isobaric) for a given length of time followed by a linear
or asymptotic approach to a final pressure

Answer 12

FALSE
it is most common

Question 13

difference between packed columns and open tubular columns

Answer 13

packed columns can provide more theoretical plates and handle larger sample volumes that open tubular columns

Question 14

TRUE or FALSE
Because of the low viscosity of supercritical
media, columns can be much longer than those used in liquid chromatography, and
column lengths of 10 to 20 m and inside diameters of 50 or 100 μm are common

Answer 14

TRUE

Question 15

The most widely used mobile phase for supercritical fluid chromatography is

Answer 15

CO2

Question 16

It is an excellent solvent for a variety of nonpolar organic molecules. In addition, it transmits in the ultraviolet and is odorless, nontoxic, widely available, and remarkably inexpensive relative to other chromatographic solvents.

Answer 16

CO2

Question 17

other substances that have served as mobile phases in SFC

Answer 17

ethane,
pentane,
dichlorodifluoromethane,
diethyl ether,
tetrahydrofuran

Question 18

TRUE or FALSE
Thus, like gas chromatography, supercritical fluid chromatography is inherently faster than liquid chromatography because of the lower viscosity and higher diffusion rates in the mobile phase

Answer 18

TRUE

Question 19

TRUE or FALSE
Supercritical fluid chromatography appears to have a niche in the spectrum of column
chromatographic methods because it can be applied to compounds that are not
readily separated by gas or liquid chromatography

Answer 19

TRUE

Question 20

TRUE or FALSE
Supercritical fluid chromatography is today not one of the primary separation methods for chiral compounds, such as those encountered in drug discovery. It has the potential to replace some of the reversed-phase HPLC separations of these compounds.

Answer 20

FALSE
Supercritical fluid chromatography is today one of the primary separation
methods for chiral compounds, such as those encountered in drug discovery. It
has the potential to replace some of the reversed-phase HPLC separations of these
compounds.

Question 21

methods include thin-layer chromatography (TLC), paper chromatography (PC), and electrochromatography. Each makes use of a flat, relatively thin layer of material that is either self-supporting or is coated on a
glass, plastic, or metal surface

Answer 21

Planar chromatographic methods

Question 22

was once called two-dimensional chromatography

Answer 22

Planar Chromatography

Question 23

can be considered a form of liquid-solid chromatography in which the stationary phase is a thin layer on the surface of an appropriate plate.

Answer 23

TLC

Question 24

common plate dimensions in centimeters of TLC plates are

Answer 24

5x20
10x20
20x20

Question 25

is the process by which a sample is carried through the stationary phase by a mobile phase. It is analogous to elution in liquid chromatography

Answer 25

Plate development

Question 26

is a separation method based on the differential rates of migration of charged species in an applied dc electric field. This separation technique for macrosize samples was first developed by the Swedish chemist Arne Tiselius in the 1930s for the study of serum proteins; he was awarded the 1948 Nobel Prize for his work

Answer 26

Electrophoresis

Question 27

has been applied to a variety of difficult analytical separation problems: inorganic anions and cations, amino acids, catecholamines, drugs, vitamins, carbohydrates, peptides, proteins, nucleic acids, nucleotides, polynucleotides, and numerous other species, which has a unique ability to separate charged macromolecules of interest to biochemists, biologists, and clinical chemists.

Answer 27

eletcrophoresis

Question 28

powerhouse method for separating proteins and nucleic acids for which it offers unparalleled resolution

Answer 28

electrophoresis

Question 29

A unique feature of capillary electrophoresis is called _________________, which the solvent migrates toward the electrode

Answer 29

electroosmotic flow.

Question 30

is usually sufficient to sweep all positive, neutral, and even negative species toward the same end of the capillary so that all can be detected as they pass by a common point

Answer 30

electroosmotic flow

Question 31

looks like a chromatogram but with narrower peaks

Answer 31

electropherogram

Question 32

is the ratio of the migration rate of an ion to the applied electric field.

Answer 32

electrophoretic mobility

Question 33

is proportional to the charge on the ion and inversely proportional to the frictional retarding force on the ion.

Answer 33

electrophoretic mobility

Question 34

TRUE or FALSE The frictional retarding force on an ion is determined by the size and shape of the ion and the viscosity of the medium

Answer 34

TRUE

Question 35

Capillary electrophoretic separations are performed in several ways called modes, such as

Answer 35

isoelectric focusing isotachophoresis capillary zone electrophoresis

Question 36

is a hybrid of HPLC and capillary electrophoresis (CE) that offers some of the best features of the two methods. Like HPLC, it applies to the separation of neutral species. Like CE, however, it provides highly efficient separations on microvolumes of sample solution without the need for the high-pressure pumping system required for HPLC

Answer 36

capillary electrochromatography