Gas Chromatography

Question 1

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

Answer 1

Gas chromatography (GC)

Question 2

principle of gas chromatography

Answer 2

partitioning equilibrium and interaction between phases

Question 3

• inert gas, typically helium or nitrogen, that ocntinuously flows through the system
• acts like a moving platform, carrying the vaporized sample components through the column

Answer 3

mobile phase (carrier gas)

Question 4

typically, what is the mobile phase (carrier gas)

Answer 4

helium or nitrogen

Question 5

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

Answer 5

stationary phase

Question 6

Two phases of the gas chromatography

Answer 6

1. stationary phase
2. mobile phase

Question 7

what happens to the sample in gas chromatography

Answer 7

• vaporized and
• caried through a colum

Question 8

strength of the interaction between sample and stationary phase is described by a value called the __ __

Answer 8

distribution constant (Kc)

Question 9

compounds with stronger interactions with stationary phase take __ to elute from the column

Answer 9

longer

Question 10

equilibrium between the concentrations of a compound in stationary phase and the mobile pase

Answer 10

• distribution constant or
• partition coefficient (Kc)

Question 11

determines the movement of compounds through the column and thus enables the chromatographic separation

Answer 11

equilibrium constant

Question 12

remove (an adsorbed substance) by washing with a solvent, especially in chromatography

Answer 12

elute

Question 13

where is the stationary phase typically coated on

Answer 13

inner walls of column

Question 14

the stationary phase is typically composed of materials like.. ?

Answer 14

silicon grease or wax

Question 15

what affects separation efficiency by mobile phase

Answer 15

flow rate

Question 16

Components of the Gas Chromatography

Answer 16

1. stationary phase
2. mobile phase
3. injector
4. detector
5. data system

Question 17

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

Answer 17

injector

Question 18

• located at the end of the column, it detects separated sample components
• monitors the eluent leaving the column and provides a signal that correspons to the concentration of the sample components

Answer 18

detector

Question 19

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

Answer 19

data system

Question 20

in gas solid chromatography, the column consists of what?

Answer 20

• hollow tube
• packed with stationary phase

Question 21

in gas-liquid chromatography, the column is what?

Answer 21

coated with thin layer of stationary phase

Question 22

Two types of columns

Answer 22

1. packed columns
2. capillary columns

Question 23

• filled with a solid support material, providing a large surface area for interactionb etween the sample components and the stationary phase
• suitable for separating less volatile compounds

Answer 23

packed columns

Question 24

• have thin, coated layer on the inner walls, providing high separation efficiency and resolving power
• ideal for separating volatile compounds

Answer 24

capillary columns

Question 25

transports the sample through the chromatographic system

Answer 25

carrier gas

Question 26

carrier gas must be __, meaning they do not react with the sample or stationary phase, to ensure accurate analysis

Answer 26

inert

Question 27

Types of inert gases

Answer 27

1. helium 2. hydrogen 3. nitrogen

Question 28

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

Answer 28

helium

Question 29

- provides higher efficiency and faster analysis compared to helium due to its lower viscosity - offers imporved separation of closely eluting compounds - however, it is flammable and requires extra safety precautions

Answer 29

hydrogen

Question 30

- inexpensive and readily available carrier gas option - less efficient than helium and hydrogen but suitable for routine analyses - often used when high-purity heloum or hydrogen is not available or cost is a concern

Answer 30

nitrogen

Question 31

Techniques for injecting samples

Answer 31

1. split injection 2. splitless injection 3. on-column injection

Question 32

- divides the smaple into two portions: one directed into the column for analysis and the other vented out - suitable for samples with a wide range of concentrations, preventing detector saturation - enhances sensitivity for trace-level analytes

Answer 32

split injection

Question 33

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

Answer 33

splitless injection

Question 34

- directly introduces the sample onto the head of the chromatographic column - suitable for thermally labile compoupnds or sample with a limited volume - minimizes sample degradation and provide sharp peak shapes

Answer 34

on-column injection

Question 35

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

Answer 35

recorder or data system

Question 36

Procedure of Gas Chromatography

Answer 36

1. sample injection and vaporization 2. separation in the column (retention time and peak analysis) 3. detection and recording of results (interpretation of chromatograms )

Question 37

where is the sample injected into

Answer 37

injection port

Question 38

time taken for a compounds to travel from injection to detection

Answer 38

retention time

Question 39

identify and quantify sample components based on their retention times and peak areas

Answer 39

peak analysis

Question 40

provides insights into sample composition, purity, and concentration

Answer 40

interpretation of chromatograms

Question 41

application of Gas chromatography sample

Answer 41

metabolomic profiling of human spermatozoa