Quiz5

Question 1

The most frequently used columns in GC are ____ columns, which come with internal diameters of ____. If we want to couple a GC column with a MS, the inner diameter of the GC column must be below a certain number because otherwise the ____ of the MS cannot be maintained.

Answer 1

open tubular (OT)
0.1-0.53mm
vacuum

Question 2

Using a wall coated open tubular (WCOT) column and a temperature program that involves heating the column to >250oC it is inevitable that the stationary liquid phase (eg. a diphenyl-dimethyl-polysiloxnae) will eventually decompose. This will result in the detection of ____ and an ____ registered by the detector. This phenomenon is also referred to as ____ and should be avoided as it will also result in a ____.

Answer 2

elevated background
reduced signal-to-noise
bleeding
tailing peaks

Question 3

Compared to OT columns, packed GC columns offer an ____ resolution. Despite this, they are the ideal choice of column if a specific compounds must be ____ from complicated mixtures (eg. in the fragrance industry).

Answer 3

inferior

isolated

Question 4

The GC detector which operates by bruning the column effluent in a H2/air flame and detects the generated ions is called ____.

Answer 4

flame ionization detector

Question 5

Splitless injection in GC refers to the fact that 80% of the sample enters the column. We use this if the analyte makes up ____ of the sample.

Answer 5

<0.01%

Question 6

In LC and at constant column length, the reduction of the particle diameter of the stationary phase will improve the ____ between two peaks and ____ the number of ____.

Answer 6

resolution
increase
theoretical plates

Question 7

It is not feasible to use open tubular columns in LC because ____ is several-fold slower in a liquid than in a gas. This also explains why high ____ is needed to force mobile phase through a packed LC column.

Answer 7

diffusion

pressure

Question 8

In 2004 a major breakthrough took place in LC when a technique was introduced that involved the utilization of stationary phase particles with a diameter of ____. This in turn required the use of much more sophisticated equipment to produce the required pressure. This technique is called ____. From a practical point of view, the utilization of smaller particles resulted in ____ times and in ____ detection limits.

Answer 8

1.5-2.0um
UPLC
shorter analysis
lower

Question 9

If we want to speed up a GC separation without decreasing the column length, we can simple change the ____.

Answer 9

temperature

Question 10

By attaching certain molecules to the silanol groups on the surface of silica particles that are used to pack an LC column, we can effectively change the ____ of the column.

Answer 10

???

Question 11

Short answer: Imagine that someone has optimized the separation of analytes on an HPLC column with a fixed length (eg. 5.0cm) filled with 1.0um particles. Describe in what way going from this column to one filled with 5.0um particles (same length) will affect: a) the retention times, b) the plate number of the column and c) the required pressure to execute the separation. Briefly explain your rationales.

Answer 11

1. Longer retention time, since diameter is larger, pathway is longer.
2. Lower pressure is required, larger particles, less force to inject solvent.
3. ???