Gas Chromatography

Question 1

• 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

Answer 1

Gas chromatography (GC)

Question 2

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

Answer 2

Differential partitioning
Stationary phase and mobile phase

Question 3

2 phases of GC

Answer 3

Mobile phase
Stationary phase

Question 4

• 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.

Answer 4

Mobile phase (Carrier gas)

Question 5

• 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

Answer 5

Stationary phase

Question 6

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

Answer 6

Stationary
Mobile

Question 7

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

Answer 7

Column

Question 8

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

Answer 8

Stationary phase
Slower
Faster

Question 9

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

Answer 9

distribution constant (Kc)

Question 10

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

Answer 10

Distribution constant (Kc)

Question 11

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

Answer 11

Stronger
Elute

Question 12

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 ?

Answer 12

distribution constant or partition coefficient (Kc)

Question 13

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

Answer 13

Movement
Separation

Question 14

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

Answer 14

Temperature
Constant

Question 15

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

Answer 15

Stationary
molecular

Question 16

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

Answer 16

Carries

Question 17

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

Answer 17

Mobile phase

Question 18

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

Answer 18

Injector

Question 19

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

Answer 19

Detector

Question 20

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

Answer 20

Eluent

Question 21

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

Answer 21

Identity
Concentration

Question 22

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

Answer 22

Data system

Question 23

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

Answer 23

Solid

Question 24

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

Answer 24

Liquid

Question 25

• 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

Answer 25

Packed columns

Question 26

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

Answer 26

Capillary columns

Question 27

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

Answer 27

Chromatographic column

Question 28

• 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

Answer 28

Carrier gas system

Question 29

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

Answer 29

Inert

Question 30

Types of carrier gases

Answer 30

Helium hydrogen nitrogen

Question 31

• 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

Answer 31

Helium

Question 32

• 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

Answer 32

Hydrogen

Question 33

• 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

Answer 33

Nitrogen

Question 34

Split injection divides the sample into two portions

Answer 34

1. directed into the column for analysis 2. vented out

Question 35

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

Answer 35

Split injection

Question 36

•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

Answer 36

Spitless injection

Question 37

• 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

Answer 37

On-column injection

Question 38

Techniques for injecting samples

Answer 38

Split injection spitless injection on column injection

Question 39

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

Answer 39

Recorder

Question 40

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

Answer 40

Recorder

Question 41

Analytical steps of GC

Answer 41

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

Question 42

Time taken for a compound to travel from injection to detection

Answer 42

Retention time

Question 43

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

Answer 43

Peak analysis

Question 44

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

Answer 44

Peaks on the chromatogram

Question 45

Provides additional information about compounds identity and purity

Answer 45

Retention times and peak shapes