Problem with liquid injections

Hi guys!

For quite a while, i've been having these issues when injecting liquid samples (solvent could be hexane or Dichloromethane) and the sample volume is set to fill the volume of the vial (about 1.4 ml). Also the syringe tip is fully inmersed when it picks up 1 uL from the vial. This problem happens randomly, it could happen every 3 or 4 injections. The first picture is the chromatogram from the sample (Wrong injection) and the second picture is the same sample, just reinyected once again under the same conditions and method (Correct injection). Does anyone have had this kind of issues before? Is there a solution I could apply to avoid this?

The instrument is an Agilent Chromatograph 7890B coupled to an Agilent 5977B Mass Spectrometer. The conditions are down below:

INSTRUMENT CONTROL PARAMETERS: CGMSDPAL
------------------------------------------

Control Information
------- -----------

Sample Inlet : GC
Injection Source : PAL Sampler
Injection Location: Front
Mass Spectrometer : Enabled


PAL3 Sampler
Installed Syringe
Name 8010-0163
Maximum Volume 10.00 µL
Minimum Volume 1.00 µL

Script Parameters
Basic
Wash Station Wash Station
Tool LS 1
Sample Volume 1 uL
Wait for System Ready At start
Wash Vial Depth 45 mm
Waste Port Depth 10 mm
Bottom Sense Off
Height From Bottom of Sample Vial 0.5 mm
Cooled Stack None
Cooled Stack Temperature 20 °C
GC Cycle Time 47 min

Pre Injection
Syringe Fill For Wash 80 %
Wash Aspirate Flow Rate 5 uL/s
Washes with Solvent 1 3
Washes with Solvent 2 3
Washes with Solvent 3 0
Washes with Solvent 4 0

Sample
Sample Vial Penetration Depth 30 mm
Sample Vial Penetration Speed 50 mm/s
Sample Washes 1
Sample Wash Volume 1 uL
Filling Strokes 4
Fill Strokes Volume 3 uL
Filling Strokes Aspirate Flow Rate 5 uL/s
Delay After Filling Strokes 0.5 s
Sample Aspirate Flow Rate 1 uL/s
Sample Post Aspirate Delay 2 s
Air Volume 1 uL
Injection Mode Normal
Injection Signal Mode Plunger Up
Inlet Penetration Depth 45 mm
Inlet Penetration Speed 100 mm/s
Pre Inject Time Delay 0 s
Injection Flow Rate 100 uL/s
Post Inject Time Delay 0 s

Post Injection
Syringe Fill For Wash 80 %
Wash Aspirate Flow 5 uL/s
Washes with Solvent 1 3
Washes with Solvent 2 3
Washes with Solvent 3 0
Washes with Solvent 4 0


Serial Number Robot
Script Name GC-LIQ-STD-V4.0

No Sample Prep method has been assigned to this method.


GC
GC Summary
Run Time 32 min
Post Run Time 10 min

Oven
Temperature
Setpoint On
(Initial) 40 °C
Hold Time 4 min
Post Run 240 °C
Program
#1 Rate 60 °C/min
#1 Value 100 °C
#1 Hold Time 0 min
#2 Rate 20 °C/min
#2 Value 120 °C
#2 Hold Time 0 min
#3 Rate 30 °C/min
#3 Value 150 °C
#3 Hold Time 0 min
#4 Rate 50 °C/min
#4 Value 200 °C
#4 Hold Time 6 min
#5 Rate 2.5 °C/min
#5 Value 230 °C
#5 Hold Time 6 min


Equilibration Time 1 min
Max Temperature 240 °C
Maximum Temperature Override Disabled
Slow Fan Disabled

Front SS Inlet He
Mode Split
Heater On 250 °C
Pressure On 7.0699 psi
Total Flow On 14 mL/min
Septum Purge Flow On 3 mL/min
Gas Saver On 20 After 1 min mL/min
Split Ratio 10 :1
Split Flow 10 mL/min
Liner Agilent 5190-2293: 900 μL (Splitless, single taper, wool, Ultra )

Thermal Aux 2 (MSD Transfer Line)
Temperature
Setpoint On
(Initial) 250 °C


Column
Column #1
Flow
Setpoint On
(Initial) 1 mL/min
Post Run 1 mL/min

DB-WAX
Temperature Range 20 °C—240 °C (240 °C)
Dimensions 30 m x 250 μm x 0.25 μm
Column lock Unlocked
In Front SS Inlet He
Out MSD
(Initial) 40 °C
Pressure 7.0699 psi
Flow 1 mL/min
Average Velocity 36.262 cm/sec
Holdup Time 1.3789 min
Control Mode Constant Flow

Column Outlet Pressure 0 psi

Signals
Signal #1:
Description None

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\etune.u
EM Setting mode Gain : 1.000000

Normal or Fast Scanning : Normal Scanning
Trace Ion Detection : Off
Run Time (if MS only) : 36 minutes

[Scan Parameters]
Start Time : 4
Low Mass : 50
High Mass : 400
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: US1828M031
---------------------------------

Trace Ion Detection is OFF.

34.593 : EMISSION
70.007 : ENERGY
4.985 : REPELLER
89.822 : IONFOCUS
20.181 : ENTRANCE_LENS
1007.142 : EMVOLTS
1029.8 : Actual EMV
1.00 : GAIN FACTOR
2724.000 : AMUGAIN
136.625 : AMUOFFSET
1.000 : FILAMENT
0.000 : DCPOLARITY
11.155 : ENTLENSOFFSET
7.252 : Ion_Body
0.203 : EXTLENS
277.000 : MASSGAIN
-23.000 : MASSOFFSET

END OF TUNE PARAMETERS
----------------------

END OF INSTRUMENT CONTROL PARAMETERS
------------------------------------

Parents
  • I assume you've already checked everything in the inlet?  Could there be little pieces of septa getting stuck in the syringe? Have you tried a new syringe? Different caps?  I feel like I've seen this before but can't remember what it was.

  • The syringe is ok, and I don't think this is the inlet since this happens only with liquid samples. I use the same liner for SPME samples and I don't have this issude.

    My first suspicion is that somehow the sample evaporates somewhere between when the syringe takes the volume from the vial and inject it into the inlet. Maybe it could be something related to the parameters set in the PAL configuration but I'm not sure.

Reply
  • The syringe is ok, and I don't think this is the inlet since this happens only with liquid samples. I use the same liner for SPME samples and I don't have this issude.

    My first suspicion is that somehow the sample evaporates somewhere between when the syringe takes the volume from the vial and inject it into the inlet. Maybe it could be something related to the parameters set in the PAL configuration but I'm not sure.

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