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ANA CHEM > Gas Chromatography > Flashcards

Gas Chromatography Flashcards

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1
Q

• Technique using analytical chemistry for separating and analyzing compounds in a complex mixtures
• it relies on the principle of differential partitioning of sample components between stationary phase and a mobile phase
• it has high sensitivity selectivity and efficiency making it an indispensable tool for qualitative and quantitative analysis of organic compounds

A

Gas chromatography (GC)

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2
Q

Gas chromatography relies on the principle of ___ ___ of sample components between a __ phase and a ___ phase

A

Differential partitioning
Stationary phase and mobile phase

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3
Q

2 phases of GC

A

Mobile phase
Stationary phase

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4
Q

• This is an inert gas typically helium or nitrogen that continuously flows through the system.
• it acts like moving platform carrying the vaporized sample components through the column.

A

Mobile phase (Carrier gas)

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5
Q

• This is a thin layer of high boiling liquid film coating the inner walls of a long, narrow column.
• it interacts with a sample components as they travel through the column

A

Stationary phase

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6
Q

Compounds have different affinities for the __ phase compared to the ___ phase

A

Stationary
Mobile

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7
Q

The sample is vaporized and carried by a gas through a ___.

A

Column

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8
Q

Inside the column the sample interacts differently with the ___ ___ causing some compounds to move ___ ( longer retention times) while others move ___

A

Stationary phase
Slower
Faster

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9
Q

The strength of this interaction in column is described by a value called the ?

A

distribution constant (Kc)

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10
Q

It represents the equilibrium between a compound in the stationary phase and the mobile phase

A

Distribution constant (Kc)

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11
Q

Compounds with ___ interactions with the stationary phase take longer to ___ (remove by washing with a solvent, especially in chromatography) from the column

A

Stronger
Elute

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12
Q

The equilibrium between the concentration of a compound in the stationary phase and the mobile phase is described by an equilibrium constant known as the ?

A

distribution constant or partition coefficient (Kc)

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13
Q

That distribution constant or partition coefficient (Kc) determines the ____ of compounds through the column and thus enables the chromatographic ____

A

Movement
Separation

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14
Q

_____ in the chemical nature of the stationary phase influences the distribution of ___

A

Temperature
Constant

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15
Q

___ phase interacts with the sample molecules differently causing separation based on ____ properties

A

Stationary
molecular

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16
Q

Mobile phase ___ the sample through the column. its flow rate affects separation efficiency.

A

Carries

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17
Q

They do not react with the sample components ensuring that the separation process is not affected by chemical interactions with the mobile phase.

A

Mobile phase

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18
Q

• it is where the sample is introduced into the system.
• It vaporizes the sample and injects it into the column.

A

Injector

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19
Q

located at the end of the column, it detects separated sample components.

A

Detector

20
Q

The detector monitors the ___ leaving the column and provides a signal that corresponds to the concentration of the sample components

A

Eluent

21
Q

The detector output is analyzed to determine the ___ and ___ of sample components

A

Identity
Concentration

22
Q

It collects and analyzes detector output, providing information about sample components’ identities and concentrations.

A

Data system

23
Q

The structure of the chromatographic column consists of a hollow tube pack with a stationary phase in gas ___ chromatography

A

Solid

24
Q

The structure of the chromatographic column consists of coated with a thin layer of stationary phase in gas ___ chromatography

A

Liquid

25
Q

• Filled with a solid support material providing a large surface area for interaction between the sample components and the stationary phase.
• they are suitable for separating less volatile compounds

A

Packed columns

26
Q

They have thin coated layer on the inner walls providing high separation efficiency and resolving power

A

Capillary columns

27
Q

Where sample components interact with the stationary phase as they pass through, leading to differential retention times and separation based on their physical and chemical properties

A

Chromatographic column

28
Q

• transports the sample through the chromatographic system
• they must be inert, meaning they do not interact with the sample or stationary phase to ensure accurate analysis
• the choice of career gas affects resolution, efficiency, and analysis time in gas chromatography

A

Carrier gas system

29
Q

Carrier gas system must be ___, meaning they do not interact with the sample or stationary phase to ensure accurate analysis

A

Inert

30
Q

Types of carrier gases

A

Helium
hydrogen
nitrogen

31
Q

• Most commonly used carrier gas due to its inertness, consistent flow rate, and road applicability
• suitable for a wide range of analytical applications and compatible with various detectors

A

Helium

32
Q

• Provides higher efficiency and faster analysis compared to helium due to its lower viscosity
• offers improve separation of closely iluting compounds
• it is flammable and requires extra safety precautions

A

Hydrogen

33
Q

• inexpensive and readily available carrier gas option
• less efficient than helium and hydrogen that suitable for routine analysis
• often use one high purity helium or hydrogen is not available or cost is concern

A

Nitrogen

34
Q

Split injection divides the sample into two portions

A
  1. directed into the column for analysis
  2. vented out
35
Q

• Suitable for samples with a wide range of concentrations preventing detector saturation
• enhances sensitivity for trace level analytes

A

Split injection

36
Q

•Introduces the entire sample into the column without splitting initially
• ideal for trace level analysis by maximizing sample concentration on the column
• ensures higher sensitivity but requires careful optimization to prevent detector overload

A

Spitless injection

37
Q

• Directly introduces the sample into the head of the chromatographic column
• suitable for thermally labile compounds or sample with a limited volume
• minimizes the sample degradation and provides short peak shapes

A

On-column injection

38
Q

Techniques for injecting samples

A

Split injection
spitless injection
on column injection

39
Q

• captures and processes chromatographic data facilitating data analysis and interpretation
• converts detector signals into digital information and generates chromatograms visual representation of analyte peaks

A

Recorder

40
Q

Converts raw chromatographic data into actionable insights, aiding in quality control, research, and various analytical applications

A

Recorder

41
Q

Analytical steps of GC

A
  1. injection of the sample into the injection port.
  2. Injected sample is vaporized by the injection ports heat and mixed with carrier gas before entering the chromatographic column
  3. Separation occurs within the chromatographic column based on differential interactions between sample components and the stationary phase
  4. Chromatograms generated by the detector are interpreted to identify sample components and assess their concentrations
42
Q

Time taken for a compound to travel from injection to detection

A

Retention time

43
Q

Involves identifying and quantifying sample components based on the retention times and peak areas

A

Peak analysis

44
Q

Represent individual compounds, with peak height or area proportional to their concentration.

A

Peaks on the chromatogram

45
Q

Provides additional information about compounds identity and purity

A

Retention times and peak shapes

ANA CHEM (8 decks)

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