Starting tips for newbie with QuEChERS

[Mr.Brown]

We are generally screening for about 120 pesticides in our samples right now

Sounds impressive hopefully one day I will also be able to screen that many
Any suggestions with which pesticides to start with?

we want to analyze honey samples
So I thought to go for the ones already reported for honey
and the ones where a MRL has been specified

[Don Shelly]

If you use internal standards it's not a big deal, but a 1 ml class A volumetric flask will work

[Don Shelly]

The pesticides are up to you. dilute your honey 1:1 with water before extracting

[Mr.Brown]

There is also some wax in honey so I should go for psa/c18/gcb clean up

I am definitely going for internal standards

[Don Shelly]

I would stay with PSA and C18, avoiding GCB when possible. GCB (and some poor quality C18s) can remove analytes.

[Mr.Brown]

I would stay with PSA and C18, avoiding GCB when possible. GCB (and some poor quality C18s) can remove analytes.

Thank you for the tip

[Camisotro]

Now a very stupid question
How are you measuring the 1mL

Graduated tubes, or if no markings, make a 1 mL mark before commencing.

[Mr.Brown]

In our lab it's 4 mL of QuEChERS exctract, add 1 mL toluene, evaporate under N2 to 0.3-0.5 mL, make up to 1 mL with toluene and add MgSO4. Mix, centrifuge, transfer for analysis.

It's also very slow evaporating that much ACN so we may see the method change further.

Hi Camisotro

Toluene seems to work to get rid of the ACN.
However I have the mass peak 91 all over the chromatogramm (splitless injecton, sampling time 0.75 min split 1:50)

Also I get some precipitation during evaporation when doing honey extraction.
I do not get the precipitation when using only blank standards in ACN.
I guess there is some stuff extracted from honey which is not that good soluble in Toluene.

Tested procedure
5g Honey
10 mL H2O
10 mL ACN
Buffered QuEChERs extraction kit
6 mL extract to QuEChERs dispersive SPE (MgSO4, PSA, C18E)
1 mL cleaned up extract + 0,5 mL Toluene
40°C, light N2 stream to roughly 0.3 mL
reconstituted to 0.5 mL

Any suggestions, thoughts?