Process Chromatography - Part A Flashcards

Flashcards covering the key concepts and terminology in Process Chromatography - Part A, including chromatography principles, components, and detectors.

What is chromatography?

A technique that separates mixtures into their components and obtains data used to monitor and control process units.

What are the two purposes of separating mixtures into their individual components?

Qualitative analysis (identifying the types of compounds) and quantitative analysis (finding the relative amounts of each component).

What are the two phases required for chromatography?

A stationary phase (holds back the components) and a mobile phase (moves them through the stationary phase).

What is Qualitative Analysis?

Identifying the types of compounds in a mixture.

What is a chromatogram?

A plot of the detector output signal on the vertical axis against time on the horizontal axis.

What two types of information does a chromatogram yield about the injected sample?

The time is taken for each component to travel through the column, and the size of the signal for each component.

What is retention time?

The time taken from sample injection to the maximum detector signal for each sample component peak.

What is a chromatograph?

The instrument that carries out chromatography.

What is the function of a carrier gas in a gas chromatograph?

To transport the sample components through the chromatograph to the detector.

List the four subgroups of chromatography based on mobile and stationary phases.

Gas Liquid Chromatography (GLC), Gas Solid Chromatography (GSC), Liquid Liquid Chromatography (LLC), Liquid Solid Chromatography (LSC).

What is Gas Liquid Chromatography (GLC)?

The most common form of chromatography in industry, used for separating mixtures of hydrocarbons and other organic compounds, using a gas mobile phase and a liquid stationary phase.

What is volatility?

The tendency of a substance to vaporize, dependent on boiling point (higher boiling point = lower volatility).

What is polarity in chemistry?

The amount of unbalanced electrical charge on a molecule.

Explain the phrase 'like dissolves like'.

Polar molecules form solutions with other polar molecules, and non-polar molecules form solutions with other non-polar molecules.

How is the concentration of a mixture component determined in a chromatograph?

It is proportional to its peak area.

What is normalization in chromatography?

A process to force the concentrations of the components to add up to 100%.

List three required properties of a carrier gas.

Must be inert, allow maximum detector response, and be available in high purity.

What is the purpose of the traps in a carrier gas system?

Moisture, oxygen, and hydrocarbon traps remove these contaminants in the carrier gas lines.

What are three common types of chromatographic valves?

Rotary, sliding plate, and diaphragm valves.

Name the four sub-groups for GC columns.

Packed GLC columns, capillary GLC columns, active solid packing GSC columns and synthetic packing GSC columns.

What is resolution in chromatography?

A unitless number that measures how far two peaks are separated.

What does column efficiency refer to?

A column's ability to separate mixtures and generate chromatograms that have small (narrow) peak widths.

Name four basic column configurations.

Backflushing, heart-cut, trap and hold, and parallel.

Describe how backflushing is used to reduce measurement delay.

The precut column is backflushed, which sends the remaining components to the detector as a group preventing the high carbon number molecules from being sent through the analysis column.

What is a flame ionization detector (FID)?

A specific detector that depends on the ability of many types of molecules to conduct an electrical current due to the charged ions that are produced when the molecules burn.

What are the two main groups of detectors?

Universal detectors respond to a physical change in the carrier gas caused by the presence of all types of sample molecules, and specific detectors respond selectively to specific types of sample molecules.

What is a thermal conductivity detector (TCD)?

detects changes in thermal conductivity in the carrier gas leaving the column. Thermal conductivity, which is the ability to conduct heat, is a physical property of the gas.

Describe Flame Photometric Detectors.

A very sensitive (ppb level) detector for sulfur compounds. After sulfur compounds separate, they leave the column with the carrier gas and burn in a hydrogen-air flame.

Describe Photoionization Detectors.

A PID replaces the flame in an FID with a ultra-violet (UV) lamp. The energy of the UV light is inversely proportional to its wavelength.