Chromatography Flashcards

What is chromatography?

Chromatography is an analytical technique that separates components in a mixture between a mobile phase and a stationary phase.

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What is chromatography?	Chromatography is an analytical technique that separates components in a mixture between a mobile phase and a stationary phase.
Describe the mobile phase in chromatography.	The mobile phase in chromatography can be a liquid or a gas.
What are the types of chromatography?	The types of chromatography include thin-layer chromatography (TLC), column chromatography (CC), and gas chromatography (GC).
How does gas chromatography work?	Gas chromatography involves packing a column with a solid or a solid coated with a liquid, and passing a gas through the column under pressure at high temperature.
What are retention times and Rf values used for?	Retention times and Rf values are used to identify different substances in chromatography.
Describe the method for thin-layer chromatography.	The method for thin-layer chromatography involves drawing a pencil line on a TLC plate, adding tiny drops of each solution to different spots, allowing the plate to air dry, placing it in a chamber with solvent, and marking the solvent level when it reaches about 1 cm from the top of the plate.
Describe two directional chromatography.	Two directional chromatography is a chromatographic technique used to separate a complex mixture with components of different solubility in solvents. It involves separating a spot of the mixture on a TLC plate with one solvent, rotating the plate 90°, and then placing it in a second solvent for a second separation.
What is the purpose of using two different solvents in two directional chromatography?	The purpose of using two different solvents in two directional chromatography is to separate components of a complex mixture that have different solubility in solvents.
Define column chromatography.	Column chromatography is a technique where a glass tube is filled with a stationary phase, usually silica or alumina, and a solvent or mixture of solvents is run through the column to separate the components of a mixture.
What does HPLC stand for?	HPLC stands for high performance liquid chromatography.
How is HPLC different from simple column chromatography?	HPLC is a type of column chromatography commonly used in industry. In HPLC, the stationary phase is a solid silica, and the mobile phase is a liquid.
What is the purpose of a filter or plug in column chromatography?	The purpose of a filter or plug in column chromatography is to retain the solid stationary phase in the glass tube.
Describe the stationary phase in HPLC.	In HPLC, the stationary phase is a solid silica.
Describe gas-liquid chromatography.	Gas-liquid chromatography is a technique used to separate mixtures of volatile liquids. The mobile phase is an inert gas, such as helium, and the stationary phase is a high boiling point liquid absorbed onto a solid.
What is the retention time in gas-liquid chromatography?	The retention time is the time taken for a particular compound to travel from the injection of the sample to where it leaves the column to the detector. It can be used to identify a substance.
How can gas-liquid chromatography be used to identify components in a mixture?	Basic gas-liquid chromatography can tell us how many components there are in the mixture by the number of peaks. The area under each peak will be proportional to the abundance of that component.
What factors can be changed to alter the retention times in gas-liquid chromatography?	The GC column temperature, column length, and flow rate can be changed to alter the retention times of substances being separated. Higher temperature or flow rate will result in shorter retention times.
What is the importance of using an inert carrier gas in gas-liquid chromatography?	It is important to use an inert carrier gas, such as helium or nitrogen, because they will not react with the components being separated in the GC column.
How can gas-liquid chromatography be combined with other machines for analysis?	Gas-liquid chromatography can be connected to a mass spectrometer, IR or NMR machine. This allows for the generation of a mass spectra, which can be analyzed or compared with a spectral database for positive identification of each component in the mixture.
What are some applications of GC-MS (gas-liquid chromatography combined with mass spectrometry)?	GC-MS is used in analysis, forensics, environmental analysis, airport security, and space probes.

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