Table of Contents
Part 1 Characteristics of volatile compound................................3
Part 2. Extraction of volatile compound......................................3
Steam distillation (non-polar volatile compound)..............................4
SAFE (thermal sensitive compound).................................................5
Headspace analysis.........................................................................6
SHS............................................................................................................................. 6
Alternative 1:SPME (low centration + both liquid/solid sample can be
applied+qualitative analysis).....................................................................................7
Alternative2: dynamic headspace sampling...............................................................8
Summary of extraction technique..............................................9
Part3 sample pre-treatment (sample preparation)....................10
Part 4. Seperation: Gas Chromatography..................................10
4.1 What type of molecule is suitable for GC?..................................10
a). what is derivatization:......................................................................................... 10
b). Why we need derivatization................................................................................10
4.2 How does gas chromatograph work?.........................................11
4.3Factor affect the efficiency in separation....................................12
4.4 Factor affect the retention of analytes in GC..............................12
1)the BP and polarity of the analyte itself.................................................................12
3) temperature of the oven (Isothermal Vs. gradient temperature)..........................15
4)length of the column.............................................................................................15
5)gas velocity........................................................................................................... 15
6)film thickness........................................................................................................ 15
Part 5: Detection: FID/ MS/ O...................................................16
Flame ionization detector........................................................16
GC MS: Electron ionization-mass spectrometry (obtain structural
information)...........................................................................16
Advantage................................................................................................................ 17
How to read the graph...................................................................18
GC-O.............................................................................................19
Other GC detector..........................................................................19
Summary of detector...............................................................19
Quantification......................................................................... 20
1
,3.1 sampling
- What do you want to know (measure)?
- Is the sample that you take representative?
- Has the sample/material been properly stored?
Problem formulation
- Which compounds?
- What are their physical/chemical properties?
- Approximate concentration?
- Other (interfering) compounds present?
- Quantitative or qualitative results?
- What accuracy and precision are required?
- Control samples available?
Extracti 1. Steam distillation (separate polar and non-polar)
on 2. SAFE (thermal sensitive)
3. Headspace:
-SHA: only for very volatile compound
-SPS: sensitive
-dynamic: very sensitive
Clean -no need for volatile, clean enough, due to extraction
(pre- technique
treatme
nt)
Separati -GC
on
Detectio -FID
n -MS: mass and identity of the molecule
-O
2
, Part 1 Characteristics of volatile compound
Feature Volatile Compounds Non-Volatile Compounds
Typical Boiling Point ~0°C to 350/400°C > 400°C
Molecular Weight Generally small Often large (polymers)
Polarity Often hydrophobic/low polarity Highly polar or charged
Examples Esters, ketones, aldehydes Sugars, salts, proteins, starch
Analysis Method Gas Chromatography (GC) Liquid Chromatography (LC)
Volatile Aroma Compounds: Typically have boiling points ranging from ~0°C to 300°C.
Gas Chromatography (GC) Limits: Compounds that can be analyzed by GC generally
have a maximum boiling point of around 350–400°C.
Part 2. Extraction of volatile compound
1. The volatile often presents at lower concentrations in food than
macronutrients (carbohydrates, fats, and proteins)
Why we don’t use regular solvent extraction for volatile
compound?
1. Solvent extraction is not preferred since it may leads to co-extration
of other molecules as well, also during evaporation of the extraction
solvent we might lose volatile
2. Solvent extraction may cause co-extraction for the volatile
compound in the food as well-----non-volatile is incompatible with GC
3
Part 1 Characteristics of volatile compound................................3
Part 2. Extraction of volatile compound......................................3
Steam distillation (non-polar volatile compound)..............................4
SAFE (thermal sensitive compound).................................................5
Headspace analysis.........................................................................6
SHS............................................................................................................................. 6
Alternative 1:SPME (low centration + both liquid/solid sample can be
applied+qualitative analysis).....................................................................................7
Alternative2: dynamic headspace sampling...............................................................8
Summary of extraction technique..............................................9
Part3 sample pre-treatment (sample preparation)....................10
Part 4. Seperation: Gas Chromatography..................................10
4.1 What type of molecule is suitable for GC?..................................10
a). what is derivatization:......................................................................................... 10
b). Why we need derivatization................................................................................10
4.2 How does gas chromatograph work?.........................................11
4.3Factor affect the efficiency in separation....................................12
4.4 Factor affect the retention of analytes in GC..............................12
1)the BP and polarity of the analyte itself.................................................................12
3) temperature of the oven (Isothermal Vs. gradient temperature)..........................15
4)length of the column.............................................................................................15
5)gas velocity........................................................................................................... 15
6)film thickness........................................................................................................ 15
Part 5: Detection: FID/ MS/ O...................................................16
Flame ionization detector........................................................16
GC MS: Electron ionization-mass spectrometry (obtain structural
information)...........................................................................16
Advantage................................................................................................................ 17
How to read the graph...................................................................18
GC-O.............................................................................................19
Other GC detector..........................................................................19
Summary of detector...............................................................19
Quantification......................................................................... 20
1
,3.1 sampling
- What do you want to know (measure)?
- Is the sample that you take representative?
- Has the sample/material been properly stored?
Problem formulation
- Which compounds?
- What are their physical/chemical properties?
- Approximate concentration?
- Other (interfering) compounds present?
- Quantitative or qualitative results?
- What accuracy and precision are required?
- Control samples available?
Extracti 1. Steam distillation (separate polar and non-polar)
on 2. SAFE (thermal sensitive)
3. Headspace:
-SHA: only for very volatile compound
-SPS: sensitive
-dynamic: very sensitive
Clean -no need for volatile, clean enough, due to extraction
(pre- technique
treatme
nt)
Separati -GC
on
Detectio -FID
n -MS: mass and identity of the molecule
-O
2
, Part 1 Characteristics of volatile compound
Feature Volatile Compounds Non-Volatile Compounds
Typical Boiling Point ~0°C to 350/400°C > 400°C
Molecular Weight Generally small Often large (polymers)
Polarity Often hydrophobic/low polarity Highly polar or charged
Examples Esters, ketones, aldehydes Sugars, salts, proteins, starch
Analysis Method Gas Chromatography (GC) Liquid Chromatography (LC)
Volatile Aroma Compounds: Typically have boiling points ranging from ~0°C to 300°C.
Gas Chromatography (GC) Limits: Compounds that can be analyzed by GC generally
have a maximum boiling point of around 350–400°C.
Part 2. Extraction of volatile compound
1. The volatile often presents at lower concentrations in food than
macronutrients (carbohydrates, fats, and proteins)
Why we don’t use regular solvent extraction for volatile
compound?
1. Solvent extraction is not preferred since it may leads to co-extration
of other molecules as well, also during evaporation of the extraction
solvent we might lose volatile
2. Solvent extraction may cause co-extraction for the volatile
compound in the food as well-----non-volatile is incompatible with GC
3
