Fall 2012 Gerstel Presentation

Report
Beyond Static Headspace:
Automated techniques to extend the limits of headspace
analysis for VOCs
Edward Pfannkoch
Director, Technology Development
Gerstel Inc.
MPS 2 Advanced Headspace
Capabilities
Advanced Headspace Injection Modes
with the MPS 2 Autosampler
 Static Headspace (SH)
 Multiple Headspace Sample Enrichment (MHSE)
 MPS-Hot Injection and Trapping Mode (HIT)
 Dynamic Headspace Sampling (DHS)
 Full Evaporation Dynamic Headspace Sampling (FEDHS)
Static Headspace Analysis
 Equilibration of the solid/liquid
samples in crimped vials at a
constant temperature
Static Headspace Analysis
 Straightforward technique for liquids





Solid samples can present challenges
Limited sensitivity
Limited vial options
Large inj volume = broad early peaks
Distribution coefficient can bias results
Multiple Headspace Sample Enrichment
(MHSE)
Several samples are taken from the same vial. The analytes are cyrofocused or focused on a packed bed liner in the PTV liner during
multiple sample Introductions.
Benefit: Improved detection limit
CIS 4 (PTV injector)
MHSE of an Herbal Based Liqueur
MPS-HIT Mode
Hot Injection and Trapping
TDU
TDU tube
Thermal Desorption Unit - TDU
No Transfer line !
Cooled Injection System - CIS
MPS-HIT Mode
 New Versions of Maestro (1.4.9.16 and up)
 Headspace and SPME Injections can be made into the TDU
 CIS can be cooled for trapping or heated for direct transfer to
the column
 For SHS, allows trapping of analytes in cold inlet while avoiding
discrimination of higher boiling components
 For SPME, allows trapping/refocusing of volatile analytes from
the fiber which can help sharpen early eluting peaks
 Allows quick change from thermal desorption to SPME or SHS
without removing the TDU
HIT with CIS Hot
HIT with CIS Cold
SLH with CIS Hot
SLH with CIS Cold
Peak #1 = 1,1-Dichloroethene
Peak #26 = 1,2-Dichlorobenzene
Dynamic Headspace (DHS)
Dynamic Headspace Option for MPS 2
Tube Types
Parameters
 Incubation temperature:
 40 °C (Coffee powder)
 25 °C (Shower gel)
 Incubation time: 5 min
 Purge flow: 20 mL/min
 Extraction time:
 10 min (Coffee powder, shower gel)
 Trap temperature: 25 °C
 Trap: TDU tube filled with Tenax-TA
 TDU temperature program: 30°C; 720°C/min; 280°C (8 min)
 TDU pneumatic setting: Splitless
 CIS temperature program: -100°C; 12°C/s; 280°C (8 min)
 CIS pneumatic setting: solvent vent (Split 10:1)
Peak areas in % (DHS = 100 %)
100 mg coffee powder – Relative Peak Areas
•%
•
100
•
90
•
80
•
70
•
•
60
50
•
40
•
30
•
•
20
10
•
0
HS
SPME
DHS
SHS and DHS
SHS is equilibrium technique which is controlled by the partitioning coefficient of
the solutes between two phases (headspace and sample matrix).
DHS prevents the establishment of an equilibration state, causing more of the
volatile dispersed in the sample matrix to leave the sample and pass into the
headspace.
TD-GC
GC
SHS
HS vial volume: 10-20 mL
Sample volume: 1-15 mL
DHS
HS vial volume: 10-20 mL
Sample volume: 1-15 mL
SHS and DHS
These techniques are generally biased toward
recovering more volatile compounds or more
hydrophobic compounds.
TD-GC
GC
SHS
HS vial volume: 10-20 mL
Sample volume: 1-15 mL
DHS
HS vial volume: 10-20 mL
Sample volume: 1-15 mL
Full Evaporation Technique (FET)
FET“Matrix
provides
more uniform
recovery
for a variety of
independent
headspace
gas chromatographic
analysis. The
evaporation
technique”
compounds
andfullsample
matrix
independent analysis.
M. Markelov, J. P. Guzowski, Analytica Chimica Acta, 276 (1993) 235.
FET is the headspace technique of introducing a small amount of sample
(mg level) and vaporizing the analytes in the headspace vial at elevated
temperatures (typically at 100 ºC), without having to rely on establishing
equilibrium between two phases.
GC
A few μL~
100℃
Fragrance profiling by FEDHS
In 2009, Hoffman et al demonstrate fragrance profiling of consumer
products by FEDHS-GC-MS [7].
Adsorbent
packed tube
A. Hoffmann
Purge gas in
Shower gel
(MeOH blend)
8 μL
80 ℃
The FEDHS-GC-MS method enables quantitative extraction of fragrance
compounds across a wide range of volatility, leading to results that are closer
to the actual fragrance composition than those obtained with other commonly
used analysis technique such as simultaneous distillation/extraction (SDE).
7) A. Hoffmann et al, GERSTEL AppNote 8/2009.
In this study, we demonstrate
uniform enrichment of a wide
FEDHS
range of odor compounds in aqueous samples by FEDHS-GC-MS.
The optimized purge condition allow complete vaporization of
100 μL of an aqueous sample, and drying it in an adsorbent
packed tube, while recovering odor compounds and leaving the
low volatile matrix behind.
Adsorbent
packed tube
Purge gas in
100 μL
80 ℃
8) N. Ochiai, K. Sasamoto, A. Hoffmann, K. Okanoya, in preparation.
Influence of purge volume on the water residue in the Tenax TA trap
Water management is very important step in FEDHS because large amount of
The purge volume of more than 2.6 L was required
water up
to
100
μL
can
be
condensed
accumulated
in the
adsorbent
trap.
100 μL of water is calculated
to and
eliminate
water. This might
be due
to re-condensation
GC-TCD response (a.u. x 1010)
to be 1.8 L of water saturated
gas at 40ºC of trap temperature.
of a part of water vapor in the vent line of the DHS module
at ambient temperature.
8
7
6
5
4
3
2
1
0
1300
1500
1700
1900
2100
2300
2500
Purge volume (mL)
2700
2900
3100
3300
Comparison of recovery between conventional DHS, HS-SPME,
and FEDHS for test odor compounds in water at 100 ng/mL
WS < log 3.0 (mg/L)
100
WS > log 3.0 mg/L
DHS
Sample: 1 mL
DHS Temp: 25ºC
Purge vol.: 3 L
60
40
DHS
Sample: 1 mL
DHS Temp: 80ºC
Purge vol.: 0.35 L
20
HS-SPME
Phenethyl
alcohol
Guaiacol
Indole
Nonalactone
Phenethyl
acetate
Linalool
Nonanal
log WS
4.51
(mg/L)
log WS
4.40
(mg/L)
log WS
4.34
(mg/L)
log WS
3.86
(mg/L)
log WS
3.18
(mg/L)
log WS
3.08
(mg/L)
log WS
2.85
(mg/L)
log WS
2.83
(mg/L)
log WS
2.11
(mg/L)
log WS
2.04
(mg/L)
Damascenone
2-Acetyl
thiazoleol
log WS
5.65
(mg/L)
Citronellol
2,5-Dimethyl
pyrazine
0
Butyrolactone
Recovery (%)
80
log WS
1.08
(mg/L)
Sample: 1 mL
Temp: 80ºC
Fiber: CAR/DVB/PDMS
Incub. time: 20 min
Ext. time: 30 min
Comparison of recovery between conventional DHS, HS-SPME,
and FEDHS for test odor compounds in water at 100 ng/mL
100
FEDHS
Sample: 0.1 mL
DHS Temp: 80ºC
Purge vol.: 3 L
80
Sample: 1 mL
DHS Temp: 25ºC
Purge vol.: 3 L
60
40
DHS
Sample: 1 mL
DHS Temp: 80ºC
Purge vol.: 0.35 L
20
HS-SPME
Phenethyl
alcohol
Guaiacol
Indole
Nonalactone
Phenethyl
acetate
Linalool
Nonanal
log WS
4.51
(mg/L)
log WS
4.40
(mg/L)
log WS
4.34
(mg/L)
log WS
3.86
(mg/L)
log WS
3.18
(mg/L)
log WS
3.08
(mg/L)
log WS
2.85
(mg/L)
log WS
2.83
(mg/L)
log WS
2.11
(mg/L)
log WS
2.04
(mg/L)
Damascenone
2-Acetyl
thiazoleol
log WS
5.65
(mg/L)
Citronellol
2,5-Dimethyl
pyrazine
0
Butyrolactone
Recovery (%)
DHS
log WS
1.08
(mg/L)
Sample: 1 mL
Temp: 80ºC
Fiber: CAR/DVB/PDMS
Incub. time: 20 min
Ext. time: 30 min
Gerstel DHS Conditions
LVFET
DHS
Incubation Time (min)
0
2
Purge Volume (mL)
1500
300
Purge Flow (mL)
50
30
Sample Volume (mL)
50
1000
Split Ratio @ CIS
Splitless
10:1
Trap Temperature: 30 deg C
Incubation Temperature 80 deg C
Tenax TA
FEDHS of Strawberry-Banana Juice
FEDHS of Carrot Juice
FEDHS of Cranberry Juice
FEDHS of Mango Coconut Water
SBSE of Coconut Water
SBSE of Flavored Coconut Water
Applications
-Analysis of off odor compounds in apple
juice by FEDHS-GC-MS
- Analysis of flavor markers in vitamin drink
Apple Juice
6200000
6000000
5800000
5600000
5400000
5200000
5000000
4800000
4600000
4400000
4200000
4000000
3800000
3600000
3400000
3200000
3000000
2800000
2600000
2400000
2200000
2000000
1800000
1600000
1400000
1200000
1000000
800000
600000
400000
200000
1
2
2
3
5
6
7
8
9
10
11
12
13
3
14
15
16
17
18
19
20
21
22
23
24
25
Butanal
17
Ethyl acetate
Acetic acid
1-Butanol
Ethyl propionate
Propyl acetate
3-Methyl butanol
2-Methyl butanol
Ethyl butyrate
Hexanal
Butyl acetate
Ethyl 2-methylbutyrate
13
Furfural
14
2-Hexenal
Cis 3-Hexenol
2-Hexenol
1-Hexanol
2-Acetyl furan
Butyrolacton
Benzaldehyde
Methyl heptenone
Hexyl acetate
Cis 3-Hexenyl acetate
Nonanal
Dihydro methyl jasmonate
*
*
16
4
*
8
2
1
2.00
4.00
6.00
56
8.00
7
11
19-23
15
10.00
12.00
*
*
9
10 12
14.00
18
16.00
18.00
25
24
20.00
22.00
24.00
26.00
28.00
Apple Juice with Off-Flavor
Overlay with reference (black trace), zoom
4000000
3500000
*
3000000
*
*
2500000
2000000
1500000
*
1000000
g-Undecalactone
g-Decalactone
500000
0
17.00
18.00
19.00
20.00
21.00
22.00
23.00
24.00
25.00
26.00
27.00
28.00
29.00
Multi Vitamin Juice
Sulfur compounds (Markers for Pineapple Juice Content)
Limonene
9000000
8500000
8000000
Methyl 3-(methylthio)-propanoate
7500000
7000000
Ethyl 3-(methylthio)-propanoate
6500000
6000000
a-Terpineol
5500000
5000000
4500000
4000000
3500000
3000000
2500000
*
*
2000000
*
1500000
*
1000000
*
500000
2.00
4.00
6.00
8.00
10.00
12.00
14.00
16.00
18.00
20.00
22.00
24.00
26.00
28.00
Multi Vitamin Juice
Sulfur compounds, extracted ion chromatogram (m/z 61, 74, 134, 148)
75000
70000
65000
60000
55000
Methyl 3-(methylthio)-propanoate
m/z 61, 74, 134
Ethyl 3-(methylthio)-propanoate
m/z 61, 74, 148
50000
45000
40000
35000
30000
25000
20000
15000
10000
5000
0
18.00
18.50
19.00
19.50
20.00
20.50
21.00
21.50
Multi Vitamin Juice
Low in Pineapple Juice Content
75000
70000
65000
60000
55000
50000
45000
40000
35000
30000
25000
Methyl 3-(methylthio)-propanoate
m/z 61, 74, 134
Ethyl 3-(methylthio)-propanoate
m/z 61, 74, 148
20000
15000
10000
5000
0
18.00
18.50
19.00
19.50
20.00
20.50
21.00
21.50
Conclusion
Using the MPS 2 autosampler with Maestro software allows
automation of the following techniques that can overcome many of
the limitations inherent to static headspace sampling:
•
Multiple Headspace Sample Enrichment (MHSE)
–
•
MPS-Hot Injection and Trapping Mode (HIT)
–
•
Improves detection limit
Full Evaporation Dynamic Headspace Sampling (FEDHS)
–
•
Improves peak shapes
Dynamic Headspace Sampling (DHS)
–
•
Improves detection limit
More uniform enrichment of analytes
SBSE for analysis of nonpolar analytes at ultralow levels
Analysis Conditions
DHS
Incubat Temp
Incubat Time
Agi On Time
Agi Off Time
Agi Speed
50°C
0 min
10 s
1s
500 rpm
Purge Volume
Purge flow
Trap Temperature
4000 mL
100 mL/min
30°C
Dry Volume
Dry Flow
Drying Temperature
0 mL
0 mL/min
30°C
Transfer Temp
150°C
Analysis Conditions
TDU
Tube Type
Carbotrap B/X
Pneumatics Mode
Sample Mode
splitless
sample remove
Temperature
Transferline Temp.
30°C (0.1 min); 720°C/min; 280°C (3 min)
320°C
Analysis Conditions
CIS 4
LN2 - Cooling
Liner Type
Glasswool
Carrier Gas
Pneumatics Mode
Vent Flow
Vent Pressure
Splitflow
Helium
solvent venting
30 mL/min
51 kPa until 0.0 min
20 mL/min @ 1.0 min
Temperature
-80°C (0.1 min); 16°C/sec; 150°C; 12°C/sec; 240°C (2 min)
Analysis Conditions
GC
Model
Agilent 7890
Column
Rxi-624Sil MS (Restek); 30 m x 0.25 mm x 1.4 µm
Mode
constant flow, 1.0 mL/min
Temperature
40°C (2 min); 5°C/min; 100°C; 10°C/min; 300°C (10 min)

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