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- Posts: 15
- Joined: Thu Jan 25, 2018 1:55 pm
I work now with the GCxGC, had previously worked with LC. I try to read but unfortunately not get any further We are struggling with shifting RT (on the first column) of all analytes. The chromatogram looks every time as shifted by 0.x min. After several runs during the day, the RT stabilize somewhat but the next day they are different again and then stabilize at a different time.
This is an Agilent 7890B with a deans switch after the first column to the MS or to the purged splitter (which then leads either to the MS or to the FID). Depending on the method we can then do the heartcuts or do a dual measurement with FID and MS in parallel.
I would be very grateful for all hints!
The method is as follows:
GC
GC Summary
Run Time 90 min
Post Run Time 20 min
Oven
Temperature
Setpoint On
(Initial) 60 °C
Hold Time 1 min
Post Run 270 °C
Program
#1 Rate 2.5 °C/min
#1 Value 240 °C
#1 Hold Time 17 min
Equilibration Time 10 min
Max Temperature 325 °C
Maximum Temperature Override Disabled
Slow Fan Disabled
ALS
Front Injector
Syringe Size 10 μL
Injection Volume 1 μL
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 1 sec
Sample Depth Disabled
Injection Type Standard
L1 Airgap 0.1 μL
Front SS Inlet He
Mode Split
Heater On 290 °C
Pressure On 297 kPa
Total Flow On 50.636 mL/min
Septum Purge Flow On 3 mL/min
Gas Saver On 20 After 3 min mL/min
Split Ratio 20 :1
Split Flow 45.367 mL/min
Thermal Aux 2 (User Configurable)
Temperature
Setpoint On
(Initial) 250 °C
Post Run 0 °C
Column
Column #1
Pressure
Setpoint On
(Initial) 297 kPa
Post Run 157 kPa
0 °C—325 °C (325 °C): 60 m x 320 μm x 0.25 μm
Column lock Unlocked
In Front SS Inlet He
Out Aux PCM C
(Initial) 60 °C
Pressure 297 kPa
Flow 2.2684 mL/min
Average Velocity 14.408 cm/sec
Holdup Time 6.9407 min
Column #2
Pressure
Setpoint On
(Initial) 240 kPa
Post Run 0 kPa
HP Wax
0 °C—325 °C (325 °C): 25 m x 250 μm x 0.25 μm
Column lock Unlocked
In Aux PCM C He
Out MSD
(Initial) 60 °C
Pressure 240 kPa
Flow 5.5945 mL/min
Average Velocity 94.89 cm/sec
Holdup Time 0.43911 min
Column Outlet Pressure 0 kPa
Front Detector FID
Makeup N2
Signal is modified by Column Compensation Curve #2
Heater On 290 °C
H2 Flow On 45 mL/min
Air Flow On 300 mL/min
Makeup Flow On 5 mL/min
Carrier Gas Flow Correction Does not affect Makeup or Fuel Flow
Flame On
Electrometer On
Valve 1
Name Deansswitch
Other On
Valve 2
Name Stopflow MSD
Other Off
PCM C
PCM C He
Pressure
Setpoint On
(Initial) 63 kPa
Post Run 0 kPa
***Excluded from Affecting GC's Readiness State***
Aux PCM C He
***Excluded from Affecting GC's Readiness State***
Aux PCM C He Supplies Column 2
Valve Box
Heater On 220 °C