Final Instrumental Exam

Front 1

FID (flame ionization detector)

Back 1

effluent is directed toward a hydrogen air flame and the molecules become pyrolyzed producing ions and electrons. Detector response is based on the current from collection of these ions and electrons.
Mass sensitive rather than concentration sensitive.
Good for detection of organic molecules.
Applicable samples: hydrocarbons
The number of ions is about proportional to the number of reduced carbon atoms in the flame.
Detection Limit: 1 pg/s
disadvantage: consumes the sample (destroys it)

Front 2

MS (mass spectrometer)

Back 2

effluent is passed through the column, fragmented, ionized, analyzed and detected.
Obtain a mass: charge ratio
Detection Limit: 0.25-100 pg

Front 3

PID (photoionization detector)

Back 3

Effluent from column is photoionized by UV radiation from a hydrogen or argon lamp. Ions and electrons are collected at a bias electrode.
Can't detect ions that have ionization potentials above the lamp energy because the compound will not absorb and thus will not be seen.
Detector most sensitive for aromatic hydrocarbons, organophosphates, organosulfur and other compounds that are ionizable by UV radiation.
Detection limit: 2 pg C/s

Front 4

ECD (electron-capture detector)

Back 4

Effluent passes over a radioactive beta-emitter which emits one electron. This electron causes carrier gas to be ionized and let go of a burst of electrons. If organic species present then the current decreases significantly because electronegative functional groups (halogens) tend to capture electrons. In absence of organic compounds current does not change.
Advantage: does not destroy the sample as compared to FID
Limit: 5 fg/s

Front 5

Thermal Conductivity

Back 5

Universal detector.
Limit 500 pg/mL

Front 6

WCOT

Back 6

Wall-Coated Open Tubular

Front 7

SCOT

Back 7

Supported-coated open tubular. This is the one that resembles a mitochondria looking thing that increases the amount of stationary phase on top (takes advantage of surface area) and increases sample capacity.

Front 8

FSWC

Back 8

Fused Silica Wall Coated (most common). Has small diameter which increases the resolution but decreases the sample capacity.

Front 9

PLOT

Back 9

Pourous Layer Open Tubular (for gas and solid chromatography)
Retention based on the absorption of gaseous substance on the solid surface.
Developed for smaller compounds that don't stick as well to the wall (big compounds stick really well but small ones don't).
Good for non-retained stuff like methane, CO, hydrogen sulfide -stuff that comes off crazy fast or has super low BP

Front 10

Normal Phase HPLC

Back 10

Stationary phase: polar
Mobile phase: non-polar
Uses up a lot of inorganic solvent

Front 11

Reversed Phase HPLC

Back 11

Stationary phase: non-polar
Mobile phase: polar
uses a lot less organic solvent

Front 12

Solution for tailing from molecules sticking to the column

Back 12

end-cap -silica based: attaching a silica molecule so it comes off more quickly