Chromatography Forum

Can someone how to do the calculations using the Luke Method in the Pesticide Analytical Manual of the USFDA?

We are being pressured to use this method but I have never done it before or have any calculations for it.

We have to use E1 or E5 (depending on sugar content) for extraction and also C1 for clean-up. But I have no calculations to apply to the reading from the MS or UV. So I am not sure if I get a reading of 2ppm from the instrument what that really means.

I would really appreciate some assistance.

You're probably better off, depending upon the pesticide(s) you're interested in, using AOAC 2007.01 rather than the Luke MRMs. There are certain compounds where Quechers would not be the method of choice, but for most pesticides residues it is infinitely easier and faster than Luke.

You're probably better off, depending upon the pesticide(s) you're interested in, using AOAC 2007.01 rather than the Luke MRMs. There are certain compounds where Quechers would not be the method of choice, but for most pesticides residues it is infinitely easier and faster than Luke.

Thanks mckrause. Can you enlightening me what types of pesticides would not be good for QuEChERS. Also what exactly are polar pesticides?

Hi Luci!

Polar pesticides are pesticides that are soluble in water. Polar pesticides and quats like paraquat and diquat, ethephon, glyphosate, fosetyl-al won't extract using QuEChERS.

Best Regards,
Don

Hi Don...Hope all is well with you...Thanks for the reply..I made a mistake I meant planar pesticides...I read some where about planar pesticides...I think...

I'm doing well Lusi! How are you?

Planar pesticides are compounds with ring structures, like DDT. They extract just fine, however they can be lost in the clean-up step if you use graphitized carbon black (GCB).

Don

Dear Don. Thanks so much, I must have read it while looking at some QuEChERS kits. I am doing ok. Still waiting that training.
Thanks a whole lot for the info one the compounds that do not do too well with the QuEChERS method.