QuEChERS - high background after cleanup in GC-MS

[Mr.Brown]

After blank (only water) QuEChERS extraction & clean up I get a very high background in GC-MS scan Mode.

So it seems that I extract a lot of compounds out of the used plastic ware.
Is this normal?
Any recommendations?

I use the SampliQ QuEChERS kit from agilent.
Extraction Kits: contains 4 g MgSO4; 1 g NaCl; 1 g NaCitrate; 0.5 g disodium citrate sesquihydrate
Cleanup Kit 1: contains 150 mg PSA, 900 mg MgSO4
Cleanup Kit 2: contains 150 mg PSA, 150 mg C18E, 900 mg MgSO4

Cleanup Kit 2 gives less background.

In both kits "Sarstedt" Tubes are used.

GC: Shimadzu 2010plus
MS: Shimadzu QP2010 Ultra
LVI using ATAS Optic-4

Injection 50µL
Split 1:100
Split Ratio Program
0.01 0.0
2.00 50.0
Puge Flow 3.0 ml/min
Carrier Gas 1.2 mL/min He
Oven
60°C to 130°C at 10°C/min
to 230°C at 4°C/min
to 300°C at 10°C/min
hold for 10 min
MSD
Interface: 300°C
Ione Source. 250°C
Solvent Cut 5 min
Voltage 0.2 kV (relative)
SCAN:
45 – 500 m/z (0.2 sec)

Autosampler
Air Volume [µL]: 0
Pre Clean with Solvent 1: 0
Pre Clean with Solvent 2: 2
Pre Clean with Sample: 1
Filling Volume [µL]: 50
Filling Speed [µL/s]: 10
Filling Strokes: 5
Pullup Delay [ms]: 5000
Injection Speed [µL/s]: 75
Pre Injection Delay [ms]: 500
Post Injection Delay [ms]: 500
Post Clean with Solvent 1: 0
Post Clean with Solvent 2: 5

Optic-4
Hot Splitless
Equil.-time: 5 sec
End time: 960 sec
Initial T: 60°C
Delay: 5 sec
Ramp: 15°C/sec
Hold T1: 280°C
Hold time: 939 sec
Vent Mode: fixed time
vent Time: 50 sec

[Mr.Brown]

blind run (Injection 50µL pure ACN)


blank extract&cleanup2 (only ACN) (Injection 50 µL)
The pink line you nearly can't see is the blind run



extract&cleanup2 (injection 50 µL)
black: blank extract (only ACN)
pink: blind run
blue: blank extract (5 mL pure Water)
brown: Honey extract


The two highest peak seem to be "9-Octadecenamide" and/or "13-Docosenamide"

[Don Shelly]

Mr. Brown,

QuEChERS was designed for GC/MS/SIM, LC/MS/MS, GC/MS/MS, TOF, etc. It was not designed for GC/MS in scan mode. The artifacts that you are seeing are to be expected.

If you require cleaner extracts, I recommend contemporary SPE or a similar technology.

Best Regards,
Don

[christophe_j]

QuEChERS are not a clean method
we use Agilent SPE in the UK we buy these from Essex Scientific Labs as we find the Agilent (formally Varian) SPE to be the best

[Mr.Brown]

I will look into SPE

Thanks for your help