direct inter-comparison of datasets obtained by different ptr-ms: a
TRANSCRIPT
Nestlé Research Center
PTR-MS Conference 2005
Direct inter-comparison of datasets obtained by different PTR-MS:
A novel approach to optimize and adapt the fragmentation pattern using a standardization
procedure
Title
Christian Lindinger, Philippe Pollien, Santo Ali, Julia Märk, and Imre Blank, Tilmann Märk
Nestlé Research Center
Agenda
Overview about PTR-MS application at Nestle NRC
On-line coffee headspaceOn-line monitoring of Maillard reactionsOff-line identification using GC-MS/PTR-MS
Outstanding problems using PTR-MS for these applications
Quantification: transmission, fragmentation-pattern
Standardization procedure
Characterizing the fragmentation-energy for reproducible measurementsEasy measurement of the transmission
PTR-MS Conference 2005
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Hot Liquid Headspace Measurement
TimeTime--resolved analysis of hot liquid headresolved analysis of hot liquid head--spacespace
Air, N2
PTR-MS
VOC + H3O+ ⌦ VOC·H+ + H2OVOC + H3O+ ⌦ VOC·H+ + H2O
H3O+
0
20
40
coun
ts-p
er-s
econ
ds
Espressox103
headspacesampling
on-line analysisby PTR-MS time-intensity profiles
PTR-MS Conference 2005
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Features:Features:
Experimental Setup
• Sample gas at high temperature• Very high VOC concentration• Water vapor saturated sample
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humidity control 1
humidity control 2
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0
20
40
coun
ts-p
er-s
econ
ds
Ristrettox103
Arpeggio
0
20
40
0 5 10 15 20 25 30
Time [min]
coun
ts-p
er-s
econ
ds
x103
Volluto
Cosi
0 5 10 15 20 25 30
Time [min]
m/z 41: 3-Methylbutanal (79%)2-Methylbutanal (21%)
m/z 61: Acetic acid (49%)Methyl formate (40%)2,3-Pentanedione (11%)
m/z 68: Pyrrole (100%)
m/z 73: 2-Butanone (100%)
m/z 75: Methyl acetate (99%)
m/z 82: 1-Methylpyrrole (100%)
m/z 87: 2-Methyl butanal (50%)Diacetyl (43%)3-Methylbutanal (7%)
m/z 97: Furfural (100%)
m/z 101: 2,3-Pentanedione (79%)2-Methyl THF (21%)
Time-intensity profiles:
Some profiles arecommon to all types
Some profiles arecharacteristic
Differentiating the Espresso-types
Coffee 1
Coffee 4
Coffee 2
Coffee 3
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0
1
2
3
4
5
6
7
8
M61/M75 M81/M97 M45/M75 M101/M68
Coffee 1Coffee 2Coffee 3Coffee 4Coffee 5Coffee 6Coffee 7Coffee 8Coffee 9Coffee 10
0
10
20
30
40
50
60
M68/M97
Mass-ratios to differentiatebetween Espressos
PTR-MS Conference 2005
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First try to find correlations between analytical data and sensory datasetsby using simple mass ratios
Sensory profiles ~ Analytical data
SensoryDescriptive:
Burnt
Woody
Cocoa
Roasted
Citrus
Winey
Flowery
Buttery
Cereal
m41/m61Cereal
0.00
0.20
0.40
0.60
0.80
1.00
1.20
COFFEE 1COFFEE 2COFFEE 3COFFEE 4COFFEE 5COFFEE 6COFFEE 7COFFEE 8COFFEE 9COFFEE 10COFFEE 11
SensorialAnalytical
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Result - Predictions implemented in an Excel sheet
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Result - Good correlation Analytic / Sensory profile
Global pattern is well preserved.
Sensory data
Analytic data
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Coffee 12
Intense
Burnt
Woody
Roasted
Cocoa
Cereal
Butter
Winey
Citrus
Flowery
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On-line monitoring of Maillard reactions
PTR-MS Conference 2005
0
500
1000
1500
2000
0 50 100 150 200 250 300Time[min]
HS
Con
c [p
pbv]
010002000300040005000600070008000
mass 45 mass 47 mass 51mass 57 mass 59 mass 71mass 75 mass 87 mass 145mass 43 mass 61
HS
Con
c. [p
pbv]
, mas
ses
43 a
nd 6
1
Experimental set-upfor Maillard PTR-MS
On-line monitoring of volatilesgenerated upon heating
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Acrylamide formation – Asparagine, Glucose, Fructose
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Can we assignion tracesto VOCs?
Can we assignion tracesto VOCs?
Espresso coffee:dynamic above-the-cup volatile profile
0
200
400
600
800
1000
1200
1400
1600
1800
2000
-4 -2 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28
Time [min]
Con
cent
ratio
n [p
pbv ]
mass 61
mass 68
mass 69
mass 73
mass 75
mass 81
mass 83
mass 87
mass 89
mass 97
mass 101
Assigning Ion Trace to VOC
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Coupling GC – EI-MS / PTR-MS(simplified scheme)
Coupling Setup
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assi
gnm
ent o
fdy
nam
ic P
TR-M
S(fr
agm
. pat
tern
)
0.0E+00
2.0E+05
4.0E+05
6.0E+05
8.0E+05
1.0E+06
1.2E+06
1.4E+06
0 5 10 15 20 25 30 35 40 45
Time [min]
Abu
ndan
ce
TIC GC-PTR-MS
0.0E+00
1.0E+06
2.0E+06
3.0E+06
4.0E+06
5.0E+06
6.0E+06 TIC GC-EI-MS
Ace
tald
ehyd
e
Met
hyl f
orm
ate
Fura
n
Furfu
ryla
lcoh
ol
1-M
ethy
lpyr
role
Furfu
ral
Ace
tic a
cid
2-TH
F-3-
one
2,3-
Pen
tane
dion
e
2,3-
But
aned
ione
3-M
ethy
lbut
anal
2-M
ethy
lbut
anal
2-B
utan
one
2-M
ethy
lfura
n
Met
hyla
ceta
techem
ical
id
entif
icat
ion
Chemical Identification
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0.0E+00
1.0E+06
2.0E+06
3.0E+06
4.0E+06
5.0E+06
6.0E+06 TIC GC-EI-MS
Ace
tald
ehyd
e
Met
hyl f
orm
ate
Fura
n
Furfu
ryla
lcoh
ol
1-M
ethy
lpyr
role
Furfu
ral
Ace
tic a
cid
2-TH
F-3-
one
2,3-
Pen
tane
dion
e
2,3-
But
aned
ione
3-M
ethy
lbut
anal
2-M
ethy
lbut
anal
2-B
utan
one
2-M
ethy
lfura
n
Met
hyla
ceta
te
0.E+00
1.E+05
2.E+05
3.E+05
4.E+05
5.E+05
6.E+05
0 5 10 15 20 25 30 35 40 45Time [min]
Inte
nsity
[cps
]
m/z 73
Compounds yieldingPTR-MS ion intensityat m/z 73
2-Methyl propanal2-Butanone
0.0E+00
2.0E+05
4.0E+05
6.0E+05
8.0E+05
1.0E+06
1.2E+06
1.4E+06
0 5 10 15 20 25 30 35 40 45
Time [min]
Abu
ndan
ce
TIC GC-PTR-MS
Example for mass 73
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Identification changes with time
PTR-MS Conference 2005
0 5 10 15 20 25 300
200
400
600
800
1000
1200
conc
entr
atio
n [p
pb]
time [min]
95 m/z 80 m/z 75 m/z 68 m/z
0
1000
2000
3000
4000
5000#5#4#3#2#1
120s trapped on Tenax
conc
entr
atio
n [p
pb]
111 m/z 101 m/z 87 m/z 73 m/z 45 m/z
5 traps during the release process Full identification of each trap
Nestlé Research Center
Some examples
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0 5 10 15 20 25 30 35 400
2x104
4x104
2% furan 2% N-ethylpyrrol96%
retention time [min]
trap #50
2x1044x104 99%
trap #40
2x1044x1046x104
100%
m/z
68
GC
-PTR
-MS
inte
nsity
trap #30
2x1044x1046x104
100%
trap #2
02x1044x1046x104
100% pyrrole
trap #1
0 5 10 15 20 25 30 35 400
5x1031x104
20%
50%21%
retention time [min]
trap #50
1x104
9%
2%3%
43%52%
trap #40
2x104
3%13%
47%
m/z
73
GC
-PTR
-MS
inte
nsity
trap #30
2x1044x104
5%16%
45%
trap #20
4x104
8x104
2% 2-methyl tetrahydrofuran-3-one2% 4-methyl-2-pentanone
39% 2-butanone
36%
34%
57%isobutanal
trap #1
0 5 10 15 20 25 30 35 400
1x105
2x105100%
99% pyridine
retention time [min]
trap #50
1x105
2x105 100%
trap #40
1x105
2x105 100%
m/z
80
GC
-PTR
-MS
inte
nsity
trap #30
1x1052x1053x105
100%
trap #20
1x1052x1053x105
trap #1
0 5 10 15 20 25 30 35 400
5x1031x1042x104
30% 2-methylbutanal
9%3-methylbutanal
67%
63%
27%
retention time [min]
trap #50
1x104
2x104
26%7%
13%
trap #40
1x104
2x104
5%16%
61%18%
m/z
87
GC
-PTR
-MS
inte
nsity
trap #30
1x104
2x104
14%2%
54%21%
trap #20
1x1042x1043x104
6%
67% 2,3-butanedione
9% gamma-butyrolactone
trap #1
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Trapping efficiencyExperimental setup
0 50 100 150 200
0.0
0.2
0.4
0.6
0.8
1.0
1.2120 s
33 m/z 45 m/z 59 m/z 61 m/z 80 m/z
norm
aliz
ed c
once
ntra
tion
trapping time [s]
preferably used trapping time
About 30% of the methanol and 50% of acetaldehyde are trapped
using a trapping time window of 2 min.
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Degradation using Tenax traps
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A well known problem of using Tenax traps is the degradation of thermo-sensible molecules. Mercaptane i.e. is an important flavor compound in coffee and suffers under thermal degradation.
The measured trapping efficiency using the above mentioned method is 70%. Injecting a well defined amount of mercaptane, a degradation of 70% was observed. Concluding: The whole setup from sampling to GC detection, 21% of the headspace concentration reaches the PTR-MS detector at the end of the GC column.
Nestlé Research Center
AgendaOverview about PTR-MS application at Nestle NRC
On-line coffee headspaceOn-line monitoring of maillard reactionsOff-line identification using GC-MS/PTR-MS
Outstanding problems using PTR-MS for these applications
Quantification: transmission, fragment-pattern
Standardization procedure
Characterizing the fragmentation-energy for reproducible measurementsEasy measurement of the transmission
PTR-MS Conference 2005
Nestlé Research Center
Problems in Quantification
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Application: Quantifying toxic compounds generated upon heating (Maillard reactions)
++
++ +=
'******
*****'
15,27323022.6
)15,273(22400013,191][
3
3
RdriftdriftOH
OHdriftR
TransEPtkInt
TransTEIntR
Needed information: IntR’+ : counts-per-seconds of ion mass corresponding to compound RIntH3O+ : counts-per-seconds of the primary ion H3O+
Trans H3O+ : transmission of quadrupole MS at the mass of the primary ion H3O+
TransR'+ : transmission of quadrupole MS at mass R’Pdrift : pressure in drift tube [bar]Tdrift : temperature in drift-tube [°C]k : reaction rate constant (2*10-9cm3/s)tdrift : reaction time (105 μs)frag : fraction of compound R at m/z R’+ (fragmentation ratio)(R’+ being any ion signal related to the protonated and eventually fragmented compound R)
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PTR-MS Conference 2005
IntR’+ : counts-per-seconds of ion mass corresponding to compound RIntH3O+ : counts-per-seconds of the primary ion H3O+
P-drift : pressure in drift tube [bar]T-drift : temperature in drift-tube [°C]
Measured data:
Literature, measured or calculated data:k : reaction rate constant (~2*10-9cm3/s)
Trans H3O+ : transmission of quadrupole MS at the mass of H3O+
TransR'+ : transmission of quadrupole MS at mass R’tdrift : reaction time (105 μs)frag : fraction of compound R at m/z R’+ (fragmentation ratio)
Influenced parameters (influenced by the settings of PTR-MS):
Where to get these values from?
Nestlé Research Center
0
0.5
1
Tran
s M
x
Compound 1 Compound 2
Tran
s M
y
PTR-MS analysis
0
5
10fra
gmen
t M
xCompound 1
Compound 2
fragm
ent
My
0.0
1.0
2.0
3.0 Ratio My / Mx
Change in fragmentation and in transmission
Inte
nsity
0
5
10
fragm
ent
Mx
Compound 1 Compound 2
fragm
ent
My
Inte
nsity
0.0
1.0
2.0
3.0 Ratio My / Mx
Inte
nsity
0.0
1.0
2.0
3.0 Ratio My / Mx
Wrongprediction
sensory profile
Problems with changing transmission of MS and changings in fragmentation.
predictionsensory profile
PTR-MS Conference 2005
Nestlé Research Center
AgendaOverview about PTR-MS application at Nestle NRC
On-line coffee headspaceOn-line monitoring of maillard reactionsOff-line identification using GC-MS/PTR-MS
Outstanding problems using PTR-MS for these applications
Quantification: transmission, fragment-pattern
Standardization procedure
Characterizing the fragmentation-energy for reproducible measurementsEasy measurement of the transmission
PTR-MS Conference 2005
Nestlé Research Center
Standardization procedure
50 50Inlet He ating Drift Tube Heating
+
_CL
U
LNT200-10
+
_CL
LNT200-10
CL
LNT200-10
CL
U
LNT200-10
CL
U
LNT200-10
CL
LNT200-10
CL
U
LNT200-10
CL
U
LNT200-10
CL
U
LNT200-10
CL
LNT200-10
4
10U
I
SNT600-1012V/2A± 15V/2AISO-AI ISO-AO
V1V2V3V4V5V6
VALVE-CTRL
powe rI
O
QMG 422
309: Act rotspd1200 Hz
DCU
309: Act rotspd1200 Hz
DCU
CHPARA
1.955E-1 mBar
SP 4SP 3SP 1 SP 21 ON
2 ON
DualGauge
PTR-MS IONICON ANALYTIK
50 50Inlet He ating Drift Tube Heating
+
_CL
U
LNT200-10
+
_CL
LNT200-10
CL
LNT200-10
CL
U
LNT200-10
CL
U
LNT200-10
CL
LNT200-10
CL
U
LNT200-10
CL
U
LNT200-10
CL
U
LNT200-10
CL
LNT200-10
4
10U
I
SNT600-1012V/2A± 15V/2AISO-AI ISO-AO
V1V2V3V4V5V6
VALVE-CTRL
powe r I
O
QMG 422
309: Act rotspd1200 Hz
DCU
309: Act rotspd1200 Hz
DCU
CHPARA
1.955E-1 mBar
SP 4SP 3SP 1 SP 21 ON
2 ON
DualGauge
PTR-MS IONICON ANALYTIK
Different PTR-MS obtaines same results
PTR-MS Conference 2005
Nestlé Research Center
Standardization procedure
50 50Inlet He ating Drift Tube Heating
+
_CL
U
LNT200-10
+
_CL
LNT200-10
CL
LNT200-10
CL
U
LNT200-10
CL
U
LNT200-10
CL
LNT200-10
CL
U
LNT200-10
CL
U
LNT200-10
CL
U
LNT200-10
CL
LNT200-10
4
10U
I
SNT600-1012V/2A± 15V/2AISO-AI ISO-AO
V1V2V3V4V5V6
VALVE-CTRL
powe rI
O
QMG 422
309: Act rotspd1200 Hz
DCU
309: Act rotspd1200 Hz
DCU
CHPARA
1.955E-1 mBar
SP 4SP 3SP 1 SP 21 ON
2 ON
DualGauge
PTR-MS IONICON ANALYTIK
Over time same results
PTR-MS Conference 2005
time
Nestlé Research Center
0
1
0 2000
2.5
0
0
80
70100
SA=1.1
SB=1.8
SC=2.1
00
Primery Ion (m/z=21)
Compound (m/z= M+1)
Transmission measurement
MFC
Compound(e.g. Acetone)
PTR-MS
MFC
Purge gas
Dilution gasSetup for controlled VOS’s flow
Increasing concentration
to PTR-MS
Time
Inte
nsity
With variouscompoundsA, B, C….
Com
poun
ds in
tens
ity
Primery Ion intensitym/z
Slop
e
Relative transmission
m/z
Transmission
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Fitting the transmission function
0 50 100 150 200 250
0.2
0.4
0.6
0.8
1.0
Equation: ((1-(1/(1+exp((x-P3)/P4))))*((1/(1+(P1^(x-P2))))^0.25)/P5) Chi^2/DoF = 0.00071 R^2 = 0.99118 P1 1.086 ±0 P2 126.19492 ±1.4018 P3 46.77031 ±1.50389 P4 37.26908 ±2.29123 P5 0.8 ±0
Tran
smis
sion
Mass [m/z]
PTR-MS 2
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New way to measure the transmission
Compoundwith many fragments
PTR-MSdirect inlet
valve
Trans-2-dodecenylacetate
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m/z
=227
[M
H]+
m/z
=167
m/z
=125m
/z=1
11m
/z=9
7m
/z=8
3m
/z=6
9m
/z=5
5m
/z=4
1
Nestlé Research Center
Measured fragmentation
0
5
10
15
20
1
41 (1
0%) 69
(15%
)
83 (5
%)
97 (6
%)
111
(12%
)12
5 (4
%)
167
(7%
)
227
(4%
)
Frag
men
tatio
n %
m/z
Example for the fragmentation pattern of Trans-2-dodecenylacetate
PTR-MS Conference 2005
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Result for Transmission
0.4
0.6
0.8
1
1
But problem….– Fragmentation is not constant
41 X
100
% /
10%
Tran
smis
sion
227
X 1
00%
/ 4%
m/z
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Fragmentation changesPTR-MS1
05
101520253035
400 450 500 550 600drift voltage [V]
rela
tive
ambu
ndan
ce [%
] m/z 41m/z 55 m/z 69m/z 83m/z 97m/z 111m/z 125m/z 167m/z 227
PTR-MS2
05
101520253035
400 450 500 550 600drift voltage [V]
rela
tive
ambu
ndan
ce [%
] m/z 41m/z 55 m/z 69m/z 83m/z 97m/z 111m/z 125m/z 167m/z 227
Δ ~ 30V
Trans-2-dodecenylacetate
PTR-MS
changing drift voltage during the measurement
400V – 600V
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How to measure the fragmentation energy
1. Compound:
Ratio of fragments independent on [H3O+] but depended on
transmission
[MY]C1* TMy
[MX]C1* TMx
2. Compound:
Compound 1 and 2 has fragments on the same masses
[MY]C2* TMy
[MX]C2* TMx
Eliminating the transmission factor
[MY]C1
[MX]C1[MY]C2
[MX]C2
FC1=
FC2=
FC1
FC2=
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Measuring the fragment-pattern
1. Compound: Trans-2-dodecenylacetate2. Compound: 3-methylbutanal
Same fragments: m/z 41 and m/z 69
cps m/z 69 / cps m/z 41
0
100
200
300
400
500
600
300 350 400 450 500 550 600drift voltage [V]
inte
nsity
3-methylbutanal
Trans-2-dodecenylacetate
PTR-MS Conference 2005
Nestlé Research Center
Fragments of Trans-2-dodecenylacetate
O
O
HO
O
+
OH
O
+
+
+
H3O+
m/z 69m/z 41
m/z 167
m/z 227
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acetic acid
Nestlé Research Center
Fragments of 3-Methylbutanal
O OH+
+
+H3O+
- H2O - C2H4
m/z 69 m/z 41m/z 87
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Eliminating the transmission
PTR-MS2 U9=6V H=2°C P=1.9mbar
00.20.40.60.8
11.21.41.6
300 350 400 450 500 550 600drift voltage [V]
inte
nsity
[MY]C1
[MX]C1[MY]C2
[MX]C2
FC1
FC2=
1.27
397 V
• Peak amplitude• Drift voltage at peak Independent from transmission
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Peak amplitude and voltage depending on U9, P-drift, humidity
1.7 1.8 1.9 2.0 2.1 2.2 2.3 2.4
360
380
400
420
440
460
480
500
Voltage at peak depending on drift pressure
PTR-MS 1 PTR-MS 2
drift
vol
tage
[V]
drift pressure [mbar]1.8 1.9 2.0 2.1 2.2 2.3
1.10
1.15
1.20
1.25
1.30
1.35
1.40
Dependence on drift pressure (P-drift):
Peak amplitude depending on drift pressure
PTR-MS 1 PTR-MS 2
inte
nsity
drift pressure [mbar]
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Peak amplitude and voltage depending on U9, P-drift, humidity
Dependence on U9 (noscone):
4 5 6 7 8 9 10 11 12 13
360
380
400
420
Voltage of peak depending on U9
PTR-MS 1 PTR-MS 2
drift
vol
tage
[V]
U9 [V]4 5 6 7 8 9 10 11 12 13
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
Peak amplitude depending on U9
PTR-MS 1 PTR-MS 2
ampl
itude
U9 [V]
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Conclusion
PTR-MS Conference 2005
Automatic standardization procedure:• Setting the U9 to optimum fragmentation pattern• Set U-drift or P-drift to defined fragmentation pattern of
Trans-2-dodecenylacetate• Measuring the transmission using the fitting function
Transfer of a characteristic value to optimize different PTR-MS (normal, HS, compact) to same fragmentation pattern
Compound 2
PTR-MSdirect inlet
valve
Compound 1 Auto optimization software
+capillaries