Pesticides in Oil

Discussions about sample preparation: extraction, cleanup, derivatization, etc.

16 posts Page 1 of 2
Good morning everyone,
I am developing a multiresident method of agrotoxics in cordia oil, and I have difficulty extracting certain compounds from the oil (which is rich in terpenes, such as alpha pinene). Some compounds just do not leave the matrix, has anyone ever worked with oil pesticides, or do you have any ideas?

Sorry for my English,
Thank you
Generally, I have had no problem with oils. Just dilute in IPA or DMSO and 'shoot'.
And you analyze by GC MS?
debora.ferreira wrote:
And you analyze by GC MS?


I have done what HPLC Chemist has suggested. When I work with oils I will usually just dilute in a miscible solvent that's compatible with GC-MS and analyze this way. I will optimize column and oven temperature from that point.
Thank you all!
I`ll try to optimize the method with ethyl acetate!
HPLC chemist wrote:
Generally, I have had no problem with oils. Just dilute in IPA or DMSO and 'shoot'.


What happens when a client asks for the detection limits in ppb or lower?

Dilute and shoot is what I would do myself, but then trying to explain why I can't deliver the same detection limit in the oil that I can in a water or soil sample becomes the headache :roll:
The past is there to guide us into the future, not to dwell in.
Debbie,

My experience with edible oils is not in the ppb range. Therefore, review and adapt the information from this page.

https://www.agilent.com/search/?Ntt=pesticides
Good afternoon!

I dilute in ethyl acetate, acetone and hexane, and get the best results in acetone.

I fortified my sample at 10 ppb and diluted 4x, I was able to read with a concentration of 2.5 ppb (GC MS / MS, MRM)

But there are some compounds that do not appear at all, which are the chlorinated compounds (BHC, Bioaletrin, Chlorprofam ...) :cry:
debora.ferreira wrote:
Good afternoon!

I dilute in ethyl acetate, acetone and hexane, and get the best results in acetone.

I fortified my sample at 10 ppb and diluted 4x, I was able to read with a concentration of 2.5 ppb (GC MS / MS, MRM)

But there are some compounds that do not appear at all, which are the chlorinated compounds (BHC, Bioaletrin, Chlorprofam ...) :cry:


Bioallethrin and Chlorprofam should both show up in GC/MS analysis. Depending on the concentration of these molecules and the array of pesticides present, it may require some more optimization. Bioallethrin in particular as many pyrethroids are very similar in structure.

Have you tried a solution of only bioallethrin or chlorprofam at higher concentrations to ensure you can find these individual molecules alone, before finding them in a matrix?
How does the liner looks like after injecting a couple of those samples? You might be losing a lot of sensitivity during the very first injection already. I think that diluting an oil only 4 times, injecting it in GCMS and looking at ppb levels of pesticides is not a very robust analysis. There is plenty of stuff in this matrix that isn't volatile and provides dirty spots for your analytes to stick to.

If you want to look at a cleaner approach, but still relatively simple, there are quechers methodes for pesticides in oil/fat samples. The trick is here to find the right disperse SPE medium, to extract as much as possible matrix from the extracts, without comprimising the recovery of the analytes. Here's an example application note.

Alternatively, sample preparation protocols based on size exclusion can yield very clean extracts of fatty samples. This requires a GPC setup though.
Bioallethrin and chlorpropham come out in my method in the solvent (acetone), but when I add in the matrix, they do not show a signal. My pesticides are all in the form of a mix (https://www.restek.com/catalog/view/41952), so I can not inject them individually.

Zoraku wrote:
debora.ferreira wrote:
Good afternoon!

I dilute in ethyl acetate, acetone and hexane, and get the best results in acetone.

I fortified my sample at 10 ppb and diluted 4x, I was able to read with a concentration of 2.5 ppb (GC MS / MS, MRM)

But there are some compounds that do not appear at all, which are the chlorinated compounds (BHC, Bioaletrin, Chlorprofam ...) :cry:


Bioallethrin and Chlorprofam should both show up in GC/MS analysis. Depending on the concentration of these molecules and the array of pesticides present, it may require some more optimization. Bioallethrin in particular as many pyrethroids are very similar in structure.

Have you tried a solution of only bioallethrin or chlorprofam at higher concentrations to ensure you can find these individual molecules alone, before finding them in a matrix?
The EMR cartridge, which is widely used for oils, whose mechanism is size exclusion, was not very efficient for my sample because my matrix is composed of small terpenes.
The liner is not very dirty.

Rndirk wrote:
How does the liner looks like after injecting a couple of those samples? You might be losing a lot of sensitivity during the very first injection already. I think that diluting an oil only 4 times, injecting it in GCMS and looking at ppb levels of pesticides is not a very robust analysis. There is plenty of stuff in this matrix that isn't volatile and provides dirty spots for your analytes to stick to.

If you want to look at a cleaner approach, but still relatively simple, there are quechers methodes for pesticides in oil/fat samples. The trick is here to find the right disperse SPE medium, to extract as much as possible matrix from the extracts, without comprimising the recovery of the analytes. Here's an example application note.

Alternatively, sample preparation protocols based on size exclusion can yield very clean extracts of fatty samples. This requires a GPC setup though.
debora.ferreira wrote:
The EMR cartridge, which is widely used for oils, whose mechanism is size exclusion, was not very efficient for my sample because my matrix is composed of small terpenes.
The liner is not very dirty.

Rndirk wrote:
How does the liner looks like after injecting a couple of those samples? You might be losing a lot of sensitivity during the very first injection already. I think that diluting an oil only 4 times, injecting it in GCMS and looking at ppb levels of pesticides is not a very robust analysis. There is plenty of stuff in this matrix that isn't volatile and provides dirty spots for your analytes to stick to.

If you want to look at a cleaner approach, but still relatively simple, there are quechers methodes for pesticides in oil/fat samples. The trick is here to find the right disperse SPE medium, to extract as much as possible matrix from the extracts, without comprimising the recovery of the analytes. Here's an example application note.

Alternatively, sample preparation protocols based on size exclusion can yield very clean extracts of fatty samples. This requires a GPC setup though.


Do the problem analytes recover well if you inject a standard in acetone following the analysis of a few samples? If the do then the problem isn't in the liner, if they don't, then matrix residues could be the problem.

I have heard Waters is developing cleanup cartridges to remove terpenes from hemp extracts, I don't know the exact part number but a co-worker who attended a conference on hemp we telling me about their presentation there.
The past is there to guide us into the future, not to dwell in.
James_Ball wrote:
debora.ferreira wrote:
The EMR cartridge, which is widely used for oils, whose mechanism is size exclusion, was not very efficient for my sample because my matrix is composed of small terpenes.
The liner is not very dirty.

Rndirk wrote:
How does the liner looks like after injecting a couple of those samples? You might be losing a lot of sensitivity during the very first injection already. I think that diluting an oil only 4 times, injecting it in GCMS and looking at ppb levels of pesticides is not a very robust analysis. There is plenty of stuff in this matrix that isn't volatile and provides dirty spots for your analytes to stick to.

If you want to look at a cleaner approach, but still relatively simple, there are quechers methodes for pesticides in oil/fat samples. The trick is here to find the right disperse SPE medium, to extract as much as possible matrix from the extracts, without comprimising the recovery of the analytes. Here's an example application note.

Alternatively, sample preparation protocols based on size exclusion can yield very clean extracts of fatty samples. This requires a GPC setup though.


Do the problem analytes recover well if you inject a standard in acetone following the analysis of a few samples? If the do then the problem isn't in the liner, if they don't, then matrix residues could be the problem.

I have heard Waters is developing cleanup cartridges to remove terpenes from hemp extracts, I don't know the exact part number but a co-worker who attended a conference on hemp we telling me about their presentation there.


I'm going to look for this Waters cartridge! See if there is anything here in Brazil!

Thanks!!
Can I suggest GPC - being the old school chemist?

Best regards,


AICMM
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