High RSD with injections from same vial

Have you confirmed whether or not you get good precision from separate vials prepared with the same solution? If separate vials provide good precision, then I wouldn't think this issue is system related.

Another thing to consider is whether there is a trend in a particular direction when injecting from the single vial. Do the injections consistently decrease/increase, or does it random? Trending in one direction would lead me to believe there is a stability issue with the sample in the punctured vial. I have had an assay where subsequent injections from a single vial are always lower, so in that case I prepare a separate vial for each injection.

Thanks Bryan I have tried it with the same solution in different vials and still have the same issue, there is no consistency it is fairly random

Under your method's Windows ***.D subdirectory is a file called "acqmeth.txt" that has all of the GC parameters, please share it.  What is the injection solvent? What sample prep?  Autosampler or manual injection? When you change the liner was it clean or were there little red particles of septum inside that result from an overtightened septum?  What is the RSD for a known standard like one of the instrument checkout samples using a known good method?   

See: (+) Proving that an Agilent GC/MS system is fully functional - Files - GC/MS - Agilent Community

Hi Paul, it is an autosampler. The liner looks totally clean. Solvent is methanol.  I don't have a checkout sample, can you suggest anything else to use to assess precision? The analytes I am look at are MDMA and Diphenylamine. I have a feeling it might be method related as opposed to the instrument but I don't know how I can assess this as a new instrument and at method development stage so have nothing to compare it to  

INSTRUMENT CONTROL PARAMETERS: GCMS-1
----------------------------------------

D:\MassHunter\Methods\MDMA cunha 70_1.m
Fri Jan 10 14:12:51 2025

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

Sample Inlet : GC
Injection Source : GC ALS
Injection Location: Front
Mass Spectrometer : Enabled

No Sample Prep method has been assigned to this method.

GC
GC Summary
Run Time 8 min
Post Run Time 1 min

Oven
Temperature
Setpoint On
(Initial) 100 °C
Hold Time 2 min
Post Run 250 °C
Program
#1 Rate 20 °C/min
#1 Value 200 °C
#1 Hold Time 1 min

Equilibration Time 1 min
Max Temperature 320 °C
Maximum Temperature Override Disabled
Slow Fan Disabled

ALS
Front Injector
Syringe Size 10 μL
Syringe 10 μL
Agilent 5181-3354
Injection Volume 1 μL
Solvent A Washes (PreInj) 3
Solvent A Washes (PostInj) 0
Solvent A Volume 8 μL
Solvent B Washes (PreInj) 0
Solvent B Washes (PostInj) 3
Solvent B Volume 8 μL
Sample Washes 0
Sample Wash Volume 8 μL
Sample Pumps 6
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 0.2 μL
Solvent Wash Mode A, B

Tray
Tray Chiller/Heater
Enable readiness check Off

Barcode Symbology Enable all symbologies
Barcode Checksum Off
Vial Heater Disabled
Vial Mixer Disabled

Jodie Please reply with all the rest of the parameters listed in that file. It includes the inlet, oven, and MS, too.

Apologies Paul I thought I had copied it all, should all be there now

INSTRUMENT CONTROL PARAMETERS: GCMS-1
----------------------------------------

D:\MassHunter\Methods\MDMA cunha 70_1.m
Fri Jan 10 14:12:51 2025

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

Sample Inlet : GC
Injection Source : GC ALS
Injection Location: Front
Mass Spectrometer : Enabled

No Sample Prep method has been assigned to this method.

GC
GC Summary
Run Time 8 min
Post Run Time 1 min

Oven
Temperature
Setpoint On
(Initial) 100 °C
Hold Time 2 min
Post Run 250 °C
Program
#1 Rate 20 °C/min
#1 Value 200 °C
#1 Hold Time 1 min

Equilibration Time 1 min
Max Temperature 320 °C
Maximum Temperature Override Disabled
Slow Fan Disabled

ALS
Front Injector
Syringe Size 10 μL
Syringe 10 μL
Agilent 5181-3354
Injection Volume 1 μL
Solvent A Washes (PreInj) 3
Solvent A Washes (PostInj) 0
Solvent A Volume 8 μL
Solvent B Washes (PreInj) 0
Solvent B Washes (PostInj) 3
Solvent B Volume 8 μL
Sample Washes 0
Sample Wash Volume 8 μL
Sample Pumps 6
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 0.2 μL
Solvent Wash Mode A, B

Tray
Tray Chiller/Heater
Enable readiness check Off

Barcode Symbology Enable all symbologies
Barcode Checksum Off
Vial Heater Disabled
Vial Mixer Disabled

Sample Overlap
Mode Sample overlap is not enabled

ALS Errors Pause for user interaction

Front SS Inlet He
Mode Split
Heater On 280 °C
Pressure On 7.1442 psi
Total Flow On 109.5 mL/min
Septum Purge Flow On 3 mL/min
Pre-Run Flow Test Off
Gas Saver On 20 mL/min after 2 min
Split Ratio 70 :1
Split Flow 105 mL/min
Liner Agilent 5190-2295: 870 μL (Split, taper, wool, low pressure drop)

Column
Column #1
Flow
Setpoint On
(Initial) 1.5 mL/min
Post Run 1 mL/min

Column Information Agilent 122-5512UI
Description DB-5ms Ultra Inert
Temperature Range -60 °C—325 °C (350 °C)
Dimensions 15 m x 250 μm x 0.25 μm (Uncalibrated)
Heater Oven
Column lock Unlocked
In Front SS Inlet He
Out MSD
(Initial) 100 °C
Pressure 7.1442 psi
Flow 1.5 mL/min
Average Velocity 64.594 cm/sec
Holdup Time 0.38703 min
Control Mode Constant Flow

Column Outlet Pressure 0 psi

Detector Evaluation
Perform Detector Evaluation Test Off

MSD Transfer Line
Temperature
Setpoint On
(Initial) 280 °C

Collision Cell/Aux
Pressure
Setpoint Off
(Initial) 10 psi
Post Run 10 psi

Quench Gas He On 4 mL/min
Collision Gas N2 On 1.5 mL/min
Collision Cell Aux He (unused)

PSD 1
Pressure
Setpoint Off
(Initial) 4.3978 psi
Post Run 60.198 psi

PSD Purge Off
PSD 1 He (unused)

Signals
Signal #1:
Description None

Signal #2:
Description None

Signal #3:
Description None

Signal #4:
Description None

Signal #5:
Description None

Signal #6:
Description None

Signal #7:
Description None

Signal #8:
Description None

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