Solid Phase Microextraction Analyses of Flavor Compounds in Foods

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Solid Phase Microextraction Analyses of Flavor
Compounds in Foods

• David B. Min
• Department of Food Science and Technology
• The Ohio State University
• Columbus Ohio

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Instrumental Analysis of Volatile Compounds

• Static headspace analysis
• Dynamic headspace analysis
• Solid phase microextraction

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Detection Limits and Reproducibility of Organic
Volatile Compounds in Water
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Definition of Solid Phase Microextraction
A technique that uses a short, thin, solid rod
of fused silica, coated with absorbent polymer
for extraction of volatile compounds
Equilibrium partitioning of the compounds between
the coating fiber and sample or headspace.
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Diagram of SPME Extraction
Direct sampling SPME
Headspace SPME
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Principles of Headspace SPME
nf Number of compounds in solid phase K
Partition coefficient Kfh Vf,Vs,Vh Volume
of solid phase, solution, and
headspace, respectively Co Initial concentration
of compounds in the solution
KfhVfVsCo
nf
Concentration of coating
Concentration of headspace
KfhVfKhsVhVs
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SPME Analysis of Volatile Compounds
Plunger
Gauge
Barrel
Solid Phase
Water bath
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Types of Solid Phases

• CB/PDMSCarboxen/Polydimethylsiloxane
• PDMS Polydimethylsiloxane
• CW/DVB Carbowax/Divinylbenzene
• PA Polyacrylate.

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Effects of Different Solid Phases on the Hexanal
Analysis in Soybean Oil
Mean
CV () CB/PDMS 499 4.2 PA 739
7.2 PDMS 966 3.2 CW/DVB
1,520 2.9 (10.7) CV
Coefficient Variation () for n 5
Hexanal Peak in Electronic Count
Significant difference (Plt0.05)
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SPME Reproducibility of Major Flavor Compounds in
Orange Juice
?-Pinene (ppm)
Octanal (ppm)
Limonene (ppm)
Decanal (ppm)
Ethyl butyrate (ppm)
Replicates
1 0.432 1.378 1.089
251.05 1.005
2 0.400 1.391 1.050
254.28 0.925
3 0.391 1.343 1.054
248.26 0.987
4 0.380 1.389 1.059
256.25 0.995
5 0.403 1.402 1.020
255.71 1.015
6 0.397 1.470 1.010
260.01 1.007
SD 0.017 0.042 0.029
4.130 0.033
ave 0.400 1.395 1.047
254.26 1.989
CV() 4.36 3.00 2.71
1.63 3.32
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Effect of Injection Temperature on Chromatograms
of Soybean Oil Volatile Compounds
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Effect of Coating Thickness on the Absorption for
the Extraction of 0.1 ppm Benzene
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Effect of Distribution Constant on the Absorption
Profile of 0.1 ppm Analyte
Kfs 831 (p-Xylene)
Kfs 294 ( Toluene)
Kfs 125 ( Benzene)
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Effect on Sample Temperature on the GC
Chromatogram of Compounds
Extracted at 25 C
Extracted at 130 C
Extracted at 200 C
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Effect of Water and Microwave Heating on the
chromatograms of Headspace Polyaromatic Compounds
1, naphthalene 2, acenaphthylene 3,
acenaphthalene 4, fluorene 5,anthracene
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Effect of Stirring Rate on the Extraction of 1
ppm Benzene in Water
2,500 rpm
400 rpm
0 rpm
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Effect of Agitation Method on the Extraction of 1
ppm Benzene in Water
Magnetic Stirring
Sonication,
No stirring
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Effect of Benzene Concentration on Extraction by
SPME
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Effect of Salts on the Extraction of Volatile
Compounds by SPME
Normalized FID Response
Benzene
Dioxane
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Matrix Effect on the Extraction of Alcohols by
SPME
Detector Response
Cltronellol
Geranlol
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Gas Chromatogram of Orange Juice Flavor by SPME
Headspace Sampling
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Regression Equations between Flavor Compounds
(ppm) and GC Peak Areas
Concentration range (ppm)
Compounds
Regression Eq
R2
Ethyl butyrate
Y0.2891X0.015
0.99
0.1-1.2
n-Octanal
Y0.4913X0.003
1.00
0.1-1.3
Decanal
Y0.2010X0.066
0.99
0.1-1.1
?-Pinene
Y0.3428X0.092
0.99
0.2-2.0
Limonene
Y17.922X9.462
0.99
20-50
Y Compound part per million, XElectronic
counts of GC peak area
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Effects of Temperature and Time on the
Equilibrium of Flavor Compounds Between the SPME
Coating and the Headspace of Orange Juice
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25C
25
40C
20
50C
FID response
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60C
10
80C
5
0
60
0
10
20
30
40
50
Adsorption Time (minutes)
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Isolation Time Effect on Soybean Oil Volatile
Compounds by SPME
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Isolation Temperature Effect on Soybean Oil
Volatile Compounds by SPME
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Chromatograms of Volatile Compounds of Soybean
Oil by SPME
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Volatile Compounds in the Headspace of Soybean
Oil by SPME-GC-MS
Compounds
Retention Time (min)
Relative ()
Pentane 1.38 3.65 Pentanal 2.06 5.31 Hexan
al 3.84 23.5 2-Butanone 3.97 9.09 Heptanal
5.90 2.70 2-Heptenal 6.45 4.76 2-Pentylfuran
8.40 4.77 2,4-Heptadienal 10.99 5.04 t-2-Oc
tenal 11.53 3.37 Nonanal 14.00 2.86 t-2-Non
enal 14.29 0.55 2-Decenal 18.69 34.3
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Effect of Isolation Temperature on Corn Oil
Volatile Compounds by SPME
25C
45C
60C
35C
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Volatile Compounds in the Headspace of Corn Oil
by SPME-GC-MS
Compounds
Retention Time (min)
Relative ()
Pentane 1.29 13.03 Pentanal 1.88 5.52 Hexa
nal 3.62 5.39 Heptanal 5.36 1.83 2-Heptenal
6.21 29.52 2-Pentylfuran 8.59 2.53 2,4-Hept
adienal 10.88 7.69 t-2-Octenal 11.51 18.07 N
onanal 13.88 6.27 t-2-Nonenal 14.23 1.33 2-
Decenal 18.61 4.93 t,t-2,4-Decadienal 20.20 1.
17 t,c-2,4-Decadienal 20.70 2.71
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Chromatograms of Soybean Oil and Corn Oil
Soybean Oil
Corn Oil
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Factors for the Sensitivity of Solid Phase
Microextraction

• Solid Phase Thickness
• Extraction Temperature and Time
• Sample Concentration
• Agitation Rate and Type
• Direct sampling versus Headspace Sampling
• Types of Solid Phases
• Types Salts and Matrix of Foods
• Optimum Ratio of Sample to Headspace Volume
• Sampling Vial Sizes

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Conclusion
The SPME-GC is a

• Reproducible
• Economic
• Simple
• Sensitive

for the analysis of volatile compounds in most
foods.
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