Transcript Presentation Title Arial 28pt Bold Agilent Blue

Troubleshooting Capillary GC
Systems
Paul Barton
Product Specialist
Consumables Division
Agilent Technologies
GC Troubleshooting
18 July 2015
“Everything was just fine and then
this happened!”
Logic = Something changed (slowly or sudden) =
Something is different
Track Events – log book
-Changed column, liner, septum, syringe, etc.
-Injected samples, other method, etc.
-Did maintenance, cut column, inlet flush, etc.
GC Troubleshooting
18 July 2015
Logical Troubleshooting

Troubleshooting Starts with Isolating the problem
There are 5 basic areas from where the problem arises
INJECTOR
FLOW
COLUMN
DETECTOR
ELECTRONICS

But of course it can always be some COMBINATION


Knowing what can & can’t cause the symptom is the key
GC Troubleshooting
18 July 2015
Isolate the Components
Put in a known good column
Move column to a different GC, inlet or
detector
Simplify the system:
- example - Direct injection instead of P&T
sample introduction
GC Troubleshooting
18 July 2015
Jumper Tube Test
Purpose
Helps to locate the source of
contamination or noise
Isolates GC components
GC Troubleshooting
18 July 2015
Jumper Tube Test
Isolate the Detector
Remove column from the detector
Cap detector and turn on
Blank run
GC Troubleshooting
18 July 2015
Jumper Tube Test
Isolation of Detector - Results
Detector OK
Detector is the problem
GC Troubleshooting
18 July 2015
Jumper Tube Test
Isolate the Injector
Connect the injector and detector
- 1-2 meters deactivated fused silica tubing
Turn on carrier gas
Blank run
GC Troubleshooting
18 July 2015
Jumper Tube Test
Isolate the Injector - Results
Injector OK
Injector, lines or carrier
gas contaminated
GC Troubleshooting
18 July 2015
Rinsing Injector
Carrier gas line
GC Oven
Injector body
MeCl2
C6
GC Troubleshooting
18 July 2015
Jumper Tube Test
Isolate the Column
Reinstall the column
Setup as before
Blank Run
GC Troubleshooting
18 July 2015
Jumper Tube Test
Isolate the Column - Results
Problem returns: It’s the column
Problem gone: Previous leak, solid debris,
or installation problem
GC Troubleshooting
18 July 2015
Typical Problems of Optimized Methods becoming
Unoptimized…and the Reason Why.
• Peak Tailing – Flow Path or Activity
• Peak Fronting – Overload or Solubility Mismatch, Injector Problems
• Split Peaks – Injector Problems, Mixed Solvent
• Ghost Peaks – In Sample or Back Flash (Carry Over)
• No Peaks – Wasn’t Introduced, Wasn’t Detected
• Response Changes – Activity, Injector Discrimination, Detector Problem
• Shifting Retention – Leaks, Column Aging, Contamination or Damage
• Loss of Resolution – Separation Decreasing, Peak Broadening
• Baseline Disturbances – Column Bleed, Contamination, Electronics
• Noisy or Spiking Baseline – Electronics or Contaminated Detector
• Quantitation Problems – Activity, Injector or Detector Problems
Tip – Don’t panic. Change one thing at a time
GC Troubleshooting
18 July 2015
No Peaks
DETECTOR (not on or not operational)
INJECTOR (not working)
-Plugged syringe/plunger not moving
-Wrong injector (or detector)
-Huge leak (older systems)
-No carrier gas flow
NOT the COLUMN Unless…
-Broken column or No column
GC Troubleshooting
18 July 2015
Peak Tailing
INJECTOR or COLUMN is Active
-Reversible adsorption of active compounds
(-OH, -NH, -SH)
FLOW problem
-dead volume, obstruction, poor installation, or
severe column contamination
Tip = Inject a light hydrocarbon, should not tail
unless flow path problem
Miscellaneous - overloading of PLOT columns, co-elution, polarity mismatch
between phase, solute or solvent, and some compounds always tail
GC Troubleshooting
18 July 2015
Peak Fronting
Shark Fin Shaped or Just Slight
COLUMN (contaminated)
-Overload (More pronounced with large
solute and phase polarity differences)
INJECTOR
-Column installation
-Compound very soluble in injection
solvent (need retention gap)
-Mixed sample solvent
OTHER
-Co-elution
-Breakdown
GC Troubleshooting
18 July 2015
Effect of Sample Overload on
Retention Time and Peak Shape
1400 ng
7 ng
8
9
10
11
min
GC Troubleshooting
18 July 2015
Ghost Peaks
Column:
DB-5
30 m x 0.53 mm I.D., 1.5 µm
125-5032
60°C for 1 min
60-300°C at 20°/min
300°C for 3 min
Helium at 36 cm/sec
Split 1:100, 250°C
sample C7 - C20
FID, 250°C
J&W P/N:
Oven:
Wh = 0.106
Carrier Gas:
Injector:
Detector:
Wh = 0.029
1.00
2.00
3.00
4.00
5.00
6.00
7.00
8.00
Wh = 0.030
9.00
10.00
11.00
12.00
13.00
14.00
GC Troubleshooting
18 July 2015
15.00
Bonus Peaks or Ghost Peaks
Contamination in INJECTOR, COLUMN or FLOW (carrier gas)
-Carry-over from a backflash or previous sample
-Bad tank of gas or traps have expired
-Septum bleed
*TIP = Run a blank run…it should be blank!
GC Troubleshooting
18 July 2015
Condensation Test
Used* to isolate the cause of:
- Erratic baselines
- Ghost peaks or carryover
*Use when problems are worse after periods of GC non-use
GC Troubleshooting
18 July 2015
Condensation Test
Procedure
Leave GC at 40-50°C for > 8 hours
Blank run
Repeat a blank run immediately after the first blank
run is complete
Compare the two blank runs
GC Troubleshooting
18 July 2015
Condensation Test
Results
First blank run is worse:
- Contaminants (from injector, lines, traps or carrier gas)
carried into the column
Blank runs the same: contaminants are not strongly
focused on the front of the column
GC Troubleshooting
18 July 2015
Split Peaks
INJECTOR (poor sample introduction)
-Injecting the sample twice (some how?)
VOLATILITY
-Sample solvent (polarity mismatch)
High boilers dropping out
on Cold Spots
-Sample in syringe needle (manual injection)
INJECTOR (activity)
-Breakdown (not really a split peak, 2 peaks)
-Transfer line temps
-Unions or fittings not
tracking column temp
-Sample degradation in injector
GC Troubleshooting
18 July 2015
PAHs in Toluene - DB-1ms
Splitting Peaks Immediately After Installation
Column:
DB-1ms
30 m x 0.25 mm I.D., 0.25 µm
123-1522
80°C for 0.8 min
80-325°C at 15°/min
325°C for 2 min
Helium at 40 cm/sec
Splitless, purge on
at .8 min, 300°C
6
Transfer line 325°C
Source 200°C
5,6
Quad 150°C
J&W P/N:
Test Temperature:
Carrier Gas:
Injector:
Detector:
1,2
8
9
7,8
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
Phenanthrene
Anthracene
Fluoranthene
Pyrene
Benzo(a)anthracene
Chrysene
Benzo(b)fluoranthene
Benzo(k)fluoranthene
Benzo(a)pyrene
Dibenz(a,h)anthracene
Benzo(g,h,I)perylene
3
10 11
4
2
1
3
4
7
9
5
11
10
7.5 8.00
8
7.50
8.5
8.50
9
9.00
9.5 10.00
10 10.50
10.5 11.00
11
11.5 12.00
12
12.5 13.00
13
13.5
14
14.5
15
15.5
9.50
11.50
12.50
13.50 14.00
14.50 15.00
15.50 16
16.00
GC Troubleshooting
18 July 2015
What can Cause all of the Peaks to Split?
Column installation
Injection technique
Sample in syringe needle
Mixed sample solvent
Sample not focusing properly
GC Troubleshooting
18 July 2015
Reinstalled the Column
Adjust the Injector Installation Distance
(previously installed too far)
Improved but still splitting
Not splitting
GC Troubleshooting
18 July 2015
Check the Flowpath
Inject Methane
GC Troubleshooting
18 July 2015
Improve Sample Focusing?
Lowered oven temperature from 80° to 50°C
Yuck!
It’s worse
8
8.00
8.50
9
9.00
9.50
10
11
12
13
14
15
16
17
10.00 10.50 11.00 11.50 12.00 12.50 13.00 13.50 14.00 14.50 15.00 15.50 16.00 16.50 17.00
Oven: 50°C for 0.8 min, 50-325°C at 15°/min, 325°C for 2 min
Carrier Gas:
Helium at 40 cm/sec
GC Troubleshooting
18 July 2015
What Could Make the Focusing Problem Worse at
a Lower Oven Temperature?
BP of Toluene = 111°C
GC Troubleshooting
18 July 2015
Improve Sample Focusing?
Increase oven temperature from 50° to 100°C
7.5
7.50
8
8.00
8.5
8.50
9
9.00
9.5
9.50
10
10.00
10.5
10.50
11
11.00
11.5
11.50
12
12.00
12.5
12.50
13
13.00
13.5
13.50
14
14.00
14.5
14.50
15
15.00
Oven: 100°C for 0.8 min, 100-325°C at 15°/min, 325°C for 2 min
Carrier Gas:
Helium at 40 cm/sec
GC Troubleshooting
18 July 2015
15.5
15.50
Peak Response
All Change in Size
INJECTOR
-Leaky syringe
-Split ratio set incorrectly
-Wrong purge activation time
-Septum purge flow too high
-Injector temperature too low
DETECTOR (response problem)
-Settings or flows changed
-Electronics failing
Tip = Ask is it all of them or some of them, if all then injector or detector
GC Troubleshooting
18 July 2015
Peak Response
Some Change in Size
INJECTOR or COLUMN is active/contaminated
-Irreversible adsorption of active compounds (-OH, -NH, -SH)
-Decomposition of sample
-Temperature Change – Discrimination
-Evaporation from sample
*Tip = If only some change, then ask which ones? If active compounds
then activity. If tracks volatility then cold spots or inlet discrimination.
GC Troubleshooting
18 July 2015
Needle Discrimination – Manual Injection
GC Troubleshooting
18 July 2015
Column Activity
FID1 A, (COLUMN_COMP\COMP000017.D)
5
pA
2
22
ZB-5MS
3
30m x 0.25mm x 0.25um
All highlighted peaks have poor peak
shape with obvious lost of responses.
20
8
18
16
11
14
10
12
9
4
10
8
6, 7
1
0
2
4
6
8
10
min
1.
Propionic acid
2. 1-Octene
3. n-Octane
4. 4-Picoline
5.
n-Nonane
6. Trimethyl phosphate
7. 1,2-Pentanediol
8. n-Propylbenzene
9.
1-Heptanol
10. 3-Octanone
11. n-Decane
Tip – Could also be liner activity
GC Troubleshooting
18 July 2015
Splitless Inlet Liners Tested
5062-3587 Single-taper, deactivated, with glass wool
5181-3316 Single-taper, deactivated (open top)
5181-3315 Dual-taper, deactivated (closed top)
G1544-80730 Direct Connect, single-taper, deactivated
G1544-80700 Direct Connect, Dual-taper, deactivated
Vendor X Unknown proprietary deactivation
Hole for EPC
GC Troubleshooting
18 July 2015
Liner Comparsion
2,4-Dinitrophenol Response Factors
160
80
20
5
ng injected
Experimental:
•
•
•
•
•
•
Agilent 6890 with FID
Column = HP-5MS 30m x 0.25mm x 0.5mm
Compared COC to various liners
0.75 min Splitless time, 3mL/min column flow
Oven: Temp programmed per 8270 method
Inj. 250°C, Det. 300°C, Sample: 1mL 8270 mix
1.400
Avg RF, RSD
0.310, 7%
0.280, 18%
1.200
0.263, 9%
0.260, 12%
Response Factor
0.229
0.216
0.191, 22%
0.800
0.167, 38%
0.280
0.125
0.253
0.316
0.332
0.318
0.328
0.328
0.331
0.261
0.072
0.170
0.214
0.303
0.284
0.400
0.197
0.218
0.228
0.207
0.200
0.000
0.311
0.278
0.207
1.000
0.600
0.325, 3%
5062-3587 5181-3316
Single-taper
(with wool)
Single-taper
(no wool)
0.277
0.287
0.328
5181-3315
Vendor X
Dual-taper
0.285
G1544-80730 G1544-80700
Direct Connect
Single-taper
Direct Connect
Dual-taper
Cool OnColumn
GC Troubleshooting
18 July 2015
Retention Time Shift
1.75
4.50
INJECTOR
-Leak in the septum
2.00
-Change in injection solvent
4.75
-Large change in sample
concentration
FLOW
3.25
3.00
2.75
-Change in gas velocity
COLUMN
5.50
-Contamination
-Damaged stationary phase
4.00
-Loss of stationary phase
-Change in temperature
GC Troubleshooting
18 July 2015
Loss of Resolution - Peak Broadening
FLOW
-Change in carrier gas velocity
-Make-up gas
COLUMN
-Contamination
-Phase degradation
INJECTOR (efficiency)
-Settings, Liner, Installation, etc.
GC Troubleshooting
18 July 2015
Loss of Resolution - Separation Decrease
COLUMN
Separation
-Different column temperature
-Contamination
-Matrix components co-eluting
-Different column phase?
Peak Width
FLOW
-Change in carrier gas velocity /
column dimensions
GC Troubleshooting
18 July 2015
Quantifying possible impact of
changing columns
Column length tolerance ±0.5 m
Tubing I.D. is normally distributed
Range = approximately 6 x Standard Deviation.
Range is ±6 µm, so 1SD = 2 µm
•1SD of 100 µm +/- 2 µm  68.3%
•2SD of 100 µm +/- 4 µm  95.5%
•3SD of 100 µm < +/- 4 µm  4.5%
GC Troubleshooting
18 July 2015
Lavender Oil, Original Method Conditions, Nominal
Dimensions
Linaly l Acetate
Method Conditions
Column: 20 m x 0.1 mm x 0.2 µm
DB-Wax
Injector: 250°C. 1:650 split, 0.5 µL
injection volume
11.610
Linalool
10.882
Lavender Oil
10.685
FID1 A, (072701A\002B0901.D)
Norm.
120
100
Carrier Gas: H2, 32 psi, 0.33 min,
5 psi/min to 45 psi, hold
10
10.5
11.5
12
12.510
12.570
12.5
12.987
12.374
11.776
11.276
11.313
11.113
11
Detector: FID, 250°C, column +
make-up (N2)n constant flow.
12.934
12.706
9.5
9.732
9.617
9
Camphre (Cam phor)
10.522
9.319
11.185
40
20
Oven: 50°C, 0.33 min
10°C/min to 200°C
200C hold until last peak elutes
12.827
60
12.217
11.463
11.542
80
min
GC Troubleshooting
18 July 2015
Lavender Oil, Camphor Spike, Original Method
Conditions, Nominal Dimensions
Lavender Oil, Spiked
10.876
10.681
FID1 A, (072701A\005B0201.D)
Norm.
120
Linaly l Acetate
11.606
Linalool
10.530
100
Camphre (Cam phor)
9.5
10
10.5
11
12
12.508
12.567
12.5
12.985
12.371
11.876
11.773
11.5
12.933
12.704
9
11.274
11.310
9.730
20
11.109
9.318
11.181
40
12.824
60
12.214
11.461
11.538
80
min
GC Troubleshooting
18 July 2015
Effects of Head Pressure on Elution Order, Same
Oven Conditions, 38 psi Head Pressure
80
11.096
Lavender Oil, Spiked, 38 psi, Constant Pressure
100
12.182
11.400
11.187
FID1 A, (072701A\005B0501.D)
Norm.
120
60
12.750
11.986
12.086
Camhpre, 11.096 min
9
9.5
10
10.5
11
11.5
12.781
12.904
12
12.465
12.332
11.861
11.655
10.248
20
9.845
9.377
9.803
11.733
40
12.5
min
GC Troubleshooting
18 July 2015
Effects of Head Pressure on Elution Order, Same
Oven Conditions, 36 psi Head Pressure
11.572
11.355
FID1 A, (072701A\005B0401.D)
Norm.
120
Lavender Oil, Spiked, 36 psi Constant Pressure
80
12.268
Camhpre, 11.290 min
11.290
12.373
100
12.928
12.162
60
9
9.5
10
10.5
11
11.5
12
12.5
12.967
12.662
12.519
12.043
11.916
11.837
10.424
20
9.967
10.019
9.546
40
min
GC Troubleshooting
18 July 2015
Effects of Head Pressure on Elution Order, Same
Oven Conditions, 34 psi Head Pressure
11.756
11.535
FID1 A, (072701A\005B0301.D)
Norm.
120
Lavender Oil, Spiked, 34 psi Constant Pressure
12.577
100
12.465
80
12.350
60
Camphre co-elutes with Linalool
9
9.5
10
11
11.5
12
12.5
12.873
12.720
12.239
12.113
10.5
12.031
20
10.612
9.727
10.144
10.207
9.137
40
min
GC Troubleshooting
18 July 2015
Effects of Head Pressure on Elution Order, Same
Oven Conditions, 30 psi Head Pressure
12.187
11.954
FID1 A, (072701A\005B0601.D)
Norm.
120
Lavender Oil, Spiked, 30 psi Constant Pressure
100
60
12.782
Camphre, co-elutes with Linalool
12.916
80
9
9.5
10
10.5
11.5
12
12.5
12.694
12.568
11
12.481
11.045
20
10.550
10.637
10.143
9.543
40
min
GC Troubleshooting
18 July 2015
Effects of Head Pressure on Elution Order, Same
Oven Conditions, 28 psi Head Pressure
12.433
12.191
FID1 A, (072701A\005B0701.D)
Norm.
120
Lavender Oil, Spiked, 28 Psi Constant Pressure
100
Camphre, 12.236 min
13.028
60
12.235
80
9
9.5
10
10.5
12.827
11
11.5
12
12.5
12.951
12.738
11.291
10.781
10.378
20
10.881
9.772
40
min
GC Troubleshooting
18 July 2015
Effects of Head Pressure on Elution Order, Same
Oven Conditions, 26 psi Head Pressure
12.706
12.456
FID1 A, (072701A\005B0801.D)
Norm.
120
Lavender Oil, Spiked, 26 psi Constant Pressure
100
12.534
80
60
Camphre, 12.534 min
9
9.5
10
10.5
11
13.023
11.566
11.038
20
11.152
10.642
10.029
40
11.5
12
12.5
min
GC Troubleshooting
18 July 2015
Column Test Chromatogram
Correct average diameter (measured with laser micrometer)
Flow rate = 1.1mL/min
Hold up time = 1.328min
Column radius = 0.25/2 = 0.125mm = 0.0125cm
Column cross-sectional area = π x 0.01252 = 4.9 x 10-4 cm2
Hold up VOLUME = 1.328 x 1.1 = 1.4608 mL
Column length =
Hold up VOLUME
Column cross-sectional area
= 1.4608 / 4.9 x 10-4
= 2981cm
GC Troubleshooting
18 July 2015
Noisy Baseline
MILD
SEVERE
FLOW
DETECTOR
-Contaminated gas
- Contaminated FID jet
-Incorrect detector settings
- Air leak - ECD, TCD
COLUMN
-Bleed if at high temperature
-In detector flame (poor installation)
GC Troubleshooting
18 July 2015
Spiking Baseline
DETECTOR
-Particles entering the detector (PLOT columns)
-Random: poor connection
-Regular: nearby "cycling" equipment (electronics)
GC Troubleshooting
18 July 2015
Quantitation Problems
DETECTOR
-Poor stability (electronics) or Baseline disturbances (contamination)
-Outside detector's linear range or wrong settings
Activity (adsorption) in INJECTOR or COLUMN
INJECTOR
OTHER
-Technique, settings, conditions
-Co-elution
-Syringe worn
-Matrix effects
-Sample evaporation – leaky vials
- BACKFLASH
-Sample decomposition
GC Troubleshooting
18 July 2015
Backflash
GC Troubleshooting
18 July 2015
Backflash – Vapor Volume Calculator
GC Troubleshooting
18 July 2015
Normal Bleed Profile
1.3e4
ALL columns bleed.
Bleed is an elevated baseline at elevated temperature
It is NOT an elevated baseline at low temperature
It is NOT peaks
1.2e4
1.1e4
1.0e4
9000
8000
7000
6000
0
5
10
Time (min.)
15
20
25
*DB-1 30m x .32mm I.D., .25µm
Temperature program // 40°C, hold 1 min // 20°/min to 320°C, hold 10 min.
GC Troubleshooting
Page 55
18 July 2015
Bleed: Why Does It Happen?
“Back Biting” Mechanism of Product Formation
H3C
CH3
Si
HO O
CH3 CH3
CH3
CH3 CH3 CH3 CH3
Si O Si O Si O Si O Si O Si O Si OH
CH3 CH3 CH3 CH3 CH3 CH3 CH3
CH3 CH3 CH3 CH3
Si O Si O Si O Si OH
CH3 CH3 CH3 CH3
+
CH3 CH3 CH3 CH3
Si O Si O Si O Si O Si
CH3 CH3 CH3 CH
3
CH3
H3C CH3
Si
O
O
CH3
Si
H3C Si
O CH
3
H3C
CH3
Si
O
CH3
CH3
Cyclic products are
thermodynamically
more stable!
Repeat
GC Troubleshooting
18 July 2015
Molecular Structure of Fragments
(a) D3 , (b) D4 , and (c) D5
.
Hexamethylcyclotrisiloxane [541-05-9]
C6H18O3Si3
MW: 222.46 - CH3= 207
Octamethylcyclotetrasiloxane [556-67-2]
C8H24O4Si4
MW: 296.62
Decamethylcyclopentasiloxane [541-02-6]
C10H30O5Si5
MG: 370.774
GC Troubleshooting
18 July 2015
Mass Spectra Showing Stationary
Phase Bleed
For 30 m x 0.25 mm, 1.0 µm d (a) 5% phenylsiloxane and (b) phenylsilarylene columns. Temperature:
325°C
GC Troubleshooting
18 July 2015
HP-5ms Customer Claim High Column Bleed
GC Troubleshooting
18 July 2015
Compare the Spectra !
GC Troubleshooting
18 July 2015
Compare the Spectra ! Part 2
GC Troubleshooting
18 July 2015
Other Sources of “Bleed Ions”
Synthetic rubbers :
Septa
Vial Septa
Solvent bottle caps
Liner O-rings
Silanized surfaces :
Deactivated liners
Deactivated vials
Column connectors / splitters
GC Troubleshooting
18 July 2015
Troubleshooting “Tools”
Test Chromatogram : ACTUAL column dimensions
Bleed Profile: baseline problems
Inject a non-retained peak: peak shape problems
Test mix: all problems
Isolate the components: all problems
Condensation Test: baseline problems
Jumper Tube Test: baseline problems
GC Troubleshooting
18 July 2015
Troubleshooting Tips
1. Isolate the problem.
(Blank Run, Inject Un-retained Compound, Jumper Tube Test)
2. Change only one variable at a time.
3. Compare before/after chromatograms.
(Peak shape, response, retention, baseline rise, background, look for trends, etc.)
4. Utilize Technical Support.
GC Troubleshooting
18 July 2015
Remember
Complete system = Carrier Gas + Injector +
Column + Detector + Data System
Multiple cause and effect
Do not change too many variables at once
Keep the system as simple as possible
GC Troubleshooting
18 July 2015
Questions?
GC Troubleshooting
18 July 2015