Hi All,
We have a py-GC-MS. Thy pyrolyzer is Frontier 3030D, GC is Agilent 7890B, and MS is Agilent 5977. We recently switched pyrolyzer to Agilent auto-sampler because we'd like to analyze liquid samples. However, since we switched from pyrolyzer back to auto-sampler, the signal of peaks is significantly reduced. The column used is a UA5 metallic column.
We suspect that this is related to a selective sampler that comes with the pyrolyzer. Even when we turn off the sampler, there might be He back flushed to the GC injector (please see more details here, https://www.frontier-lab.com/assets/file/technical-note/PYT-036E.pdf)
I wonder if anyone could give us some suggestions? Would increasing the gain factor be a good idea?
Below is the method we used:
GC
GC Summary
Run Time 65 min
Post Run Time 20 min
Oven
Temperature
Setpoint On
(Initial) 50 °C
Hold Time 5 min
Post Run 350 °C
Program
#1 Rate 5 °C/min
#1 Value 350 °C
#1 Hold Time 0 min
Equilibration Time 3 min
Max Temperature 350 °C
Maximum Temperature Override Disabled
Slow Fan Disabled
ALS
Front Injector
Syringe Size 10 μL
Injection Volume 1 μL
Solvent A Washes (PreInj) 3
Solvent A Washes (PostInj) 3
Solvent A Volume 8 μL
Solvent B Washes (PreInj) 3
Solvent B Washes (PostInj) 3
Solvent B Volume 8 μL
Sample Washes 3
Sample Wash Volume 8 μL
Sample Pumps 3
Dwell Time (PreInj) 0 min
Dwell Time (PostInj) 0 min
Solvent Wash Draw Speed 300 μL/min
Solvent Wash Dispense Speed 3000 μL/min
Sample Wash Draw Speed 300 μL/min
Sample Wash Dispense Speed 3000 μL/min
Injection Dispense Speed 6000 μL/min
Viscosity Delay 0 sec
Sample Depth Disabled
Injection Type Standard
L1 Airgap 0.2 μL
Solvent Wash Mode A, B
Sample Overlap
Mode Sample overlap is not enabled
ALS Errors Pause for user interaction
Front SS Inlet He
Mode Split
Heater On 250 °C
Pressure On 12.024 psi
Total Flow On 147.39 mL/min
Septum Purge Flow On 3 mL/min
Gas Saver Off
Split Ratio 100 :1
Split Flow 142.96 mL/min
Liner A Liner has not been selected.
Thermal Aux 2 (MSD Transfer Line)
Temperature
Setpoint On
(Initial) 250 °C
Column
Column #1
Pressure
Setpoint On
(Initial) 12.024 psi
Post Run 12.024 psi
Temperature Range -60 °C—360 °C (380 °C)
Dimensions 30 m x 250 μm x 0.25 μm
Column lock Unlocked
In Front SS Inlet He
Out MSD
(Initial) 50 °C
Pressure 12.024 psi
Flow 1.4296 mL/min
Average Velocity 43.575 cm/sec
Holdup Time 1.1475 min
Control Mode Constant Pressure
Column Outlet Pressure 0 psi
Signals
Signal #1: Test Plot
Description Test Plot
Save Off
Data Rate 50 Hz
Signal #2:
Description None
Signal #3:
Description None
Signal #4:
Description None
MS Information
-- -----------
General Information
------- -----------
Acquisition Mode : Scan
Solvent Delay (minutes) : 4
Tune file : D:\MassHunter\GCMS\1\5977\ATUNE.U
EM Setting mode Gain : 1.000000
Normal or Fast Scanning : Normal Scanning
Trace Ion Detection : Off
Run Time (if MS only) : 45 minutes
[Scan Parameters]
Start Time : 4
Low Mass : 30
High Mass : 800
Threshold : 150
A/D Samples: : 4
[MSZones]
MS Source : 230 C maximum 250 C
MS Quad : 150 C maximum 200 C
Timed Events
----- ------
Number Events= 0
END OF MS ACQUISITION PARAMETERS
TUNE PARAMETERS for SN: US1513L405
---------------------------------
Trace Ion Detection is OFF.
34.593 : EMISSION
70.007 : ENERGY
31.911 : REPELLER
90.331 : IONFOCUS
15.136 : ENTRANCE_LENS
1266.252 : EMVOLTS
1335.1 : Actual EMV
1.00 : GAIN FACTOR
993.000 : AMUGAIN
100.250 : AMUOFFSET
1.000 : FILAMENT
0.000 : DCPOLARITY
13.566 : ENTLENSOFFSET
0.000 : Ion_Body
0.000 : EXTLENS
-756.000 : MASSGAIN
-43.000 : MASSOFFSET
Thank you so much for your help in advance!
You may need to flush out the column, reboot/re-install the program, and re-validate the performance with standard validated samples. Hope that works.
Follow up: We found out that the syringe was slightly crooked. After changing the syringe on the auto-sampler, the intensity resumes normal now.
Sounds about right. There seemed to be less sample mass loading on the column. Glad to see that you figured it out.
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