Chromatography Part B Flashcards
What type of valve does liquid chromatography typically uses?
Rotary valve designed to be leak-free under high pressure
What is the purpose of the guard column in liquid chromatography?
A short column (20 mm or 1 inch) placed before the main column that protects the main column from being plugged by solids
What is used to analyze water samples for their cations and anions?
Ion Exchange Columns
What are the most common LC detectors?
1) Refractive Index Detector
2) Optical Absorbance Detector
3) Ultraviolet Fluorescence Detector
4) Electrical Conductivity Detector
Bending light rays at a boundary between 2 different transparent materials is called __________.
Refraction
A _________ detector measures the change in conductivity that occurs due to sample ions.
Electrical Conductivity
What types of filters can be used as a guard filter?
In-line filter
What 2 problems are posed by a multi-stream sample system?
1) Chromatograph failure results in loss of data for multiple streams
2) Multi-stream switching systems are complex and require more maintenance
What is the purpose of back purging in a multi-stream sample system?
To decrease cross-contamination between multiple streams
What is the purpose of continuous flow in a multi-stream sample system?
To decrease time delay of the system
What are the 4 types of electrical safety protection that allow a process chromatograph to be used in hazardous areas?
1) Intrinsically safe protection
2) Purging
3) Pressurization
4) Explosion-proof housing
What is the sequence that an operator must follow to turn on the chromatograph?
1) Turn on instrument air flow
2) Purge the enclosures
3) Establish carrier gas flow
4) Turn on electrical power
What 2 chromatography detectors require Hydrogen gas?
FID and FPD
What scenario requires the use of HPLC instead of GC?
1) When samples can not be vaporized such as inorganic salts (Sodium Hydroxide).
2) When materials decompose due to heat such as high molecular weight polymers
What are the 3 disadvantages with using HPLC?
1) Due to high pressures maintenance becomes harder
2) Each type of sample requires its own special solvent, column and detector
3) Column separation requires extensive chemical knowledge
