Chapter 5 - UHPLC

Question 1

Column back pressure is inversely proportional to

Answer 1

d_p²

Question 2

Mass sensitivity

Answer 2

The minimum amount of mass that is injected to yield a signal that is three times those of the baseline noise.

Question 3

Concentration sensitivity

Answer 3

is defined by the LOD based on sample concentration and remains independent of column size when the sample injection volume is scaled to VM.

Question 4

Most HPLC autosamplers are capable of peak area precision levels of ______% relative standard deviation (RSD) for injection volumes >5 μl.

Answer 4

0.2-0.5%

Question 5

Most UHPLC autosamplers are capable of peak area precision levels of _______% relative standard deviation (RSD) for injection volumes >1 μl.

Answer 5

0.1-0.2%

Question 6

3 primary benefits of UHPLC

Answer 6

1. Fast separation with good resolution
2. High resolution analysis of complex samples
3. Rapid HPLC method development

Question 7

Radial thermal gradient

Answer 7

The center of the column has higher temperatures since heat dissipates from the wall more quickly.

Question 8

Longitudinal thermal gradient

Answer 8

Heat generated is cumulative where heats at the column outlet can be 5-20^o C higher than the inlet.

Question 9

Viscous heating is likely only a problem for columns packed with

Answer 9

very small particles operating at very high pressure.