Chromatography Forum

Hello All,

I am supposed to be working on neonicotinoids (imidacloprid, dinotefuran, imidacloprid, thiacloprid, thiamethoxam, clothianidin) by GC/MS but am having trouble with low response. I have also had an issue finding articles detailing methods by GC, most seem to be using an LC/MS.

I have 3 Aginlent 7890s each equipped with 5975C, 5977A, and 7000 MS/MS. I am considering NCI or derivatization but without some guidance its just a shot in the dark.

Does anyone have any experience with these compounds on a GC?

We will eventually need to extract these compounds out of water with a DCM shakeout if anyone has tips on that too.

There's a good reason people measure them on LCMS. If they don't decompose in your inlet they will show plenty of tailing. It's a GC problem, switching from EI to NCI-MS will not give a difference.

The only thing you can if you insist on GCMS is derivatize. There are probably derivatization methods for neonicotinoids if you look around.

Clothianidin is especially poor by GC-MS. You are much better off using LC-MS/MS for this class of compounds. We have run them both ways, and the difference in the results is pretty stunning. Even on older LC-MS/MS equipment (I run an old Waters Quattro Micro) the sensitivity blow GC-MS away.

Rndirk wrote:
There's a good reason people measure them on LCMS. If they don't decompose in your inlet they will show plenty of tailing. It's a GC problem, switching from EI to NCI-MS will not give a difference.

The only thing you can if you insist on GCMS is derivatize. There are probably derivatization methods for neonicotinoids if you look around.

The peak tailing is not so much a GC problem as an problem of injection. Most people don't care about the inlet, but a fresh liner with a good heat-shield and a proper installed column can get rid of most of the peak tailing. I understand if you don't want to switch to LC-MS/MS, then you should try to max out the 7000...you got a triple quad there so make the most of it and you will be able to get near the LC-MS sensitivity. Just don't be afraid to change specially in the injection part, maybe a PTV would be beneficial? or Head-Space?

Thank you all for the responses. I am aware LC-MS/MS is the preferred method, but my bosses refuse to buy one and want everything done by GC/MS.

Derivatization is something I plan to try if I can find a good method online somewhere. I do not think these compounds are volatile enough for headspace but PTV is a possibility.

I ran them on NCI over the weekend and some of the results are decent. It looks as if my sensitivity problems are with Dinotefuran and Imidacloprid with almost 0 counts. Clothianidin is giving me split peaks but I should be able to work with that

With the 7890/7000 you may want to look at the MMI injector and do large volume injections with solvent venting, you can increase sensitivity quite a bit that way. Also peak shapes can be improved by using a short guard column of the correct polarity and letting the solvent focus in the guard column to give tighter elution bands.

The problem is going to be the very high boiling points and low vapor pressures keeping them from doing well in GC.

If anyone is interested I have developed a decent acquisition method using MRM.

These compounds do have very high boiling points so I increased the inlet temp to about 360C and that really boosted my transfer onto the column. Then, using the selectivity of MRM I have decent sensitivity for these compounds.

It may not be as good as LC/MS/MS but it does seem to work

I occasionally work with various neonics and would certainly be interested in your methodology - like you we only have a GC/MS so we routinely will either send samples out or do what we can via HPLC.

Honestly, a regular GCMS was not sufficient to achieve the detection limits I needed (ppt in water). I have seen methods with higher detection limits using a GCMS but if you need to go to low levels you will probably need an MS/MS or as you stated an HPLC

Some of the compounds (clothianidin, acetamiprid, thiacloprid, thiamethoxam) work quite nicely in NCI. Imidacloprid and dinotefuran did not seem to ionize that way so we went back to trying EI and MRM. If MRM had not worked I was going to try PCI so that may be worth a shot for you.

The key seems to be that these compounds have very low vapor pressure and boiling points. Eventually, we determined we were just not getting much onto the column from the inlet set at 285C. I started to try higher temps and could see my abundances rise dramatically. I think I ended up at 360C for the inlet but I'm sure you increase the temp even higher. Then the collision cell does the filtering work for you so one can be confident even with low area counts

Feel free to message me if that did not answer your question

PhysisGC wrote:
If anyone is interested I have developed a decent acquisition method using MRM.

These compounds do have very high boiling points so I increased the inlet temp to about 360C and that really boosted my transfer onto the column. Then, using the selectivity of MRM I have decent sensitivity for these compounds.

It may not be as good as LC/MS/MS but it does seem to work

Hi!
I'm trying to do simultaneous analysis of neonicotinoids with other pesticides using GCMS. Did you do derivatization for the analysis? What kind of derivative agents did you use in the analysis?
i'd tried to reach you out through your contact in this forum but i couldn't send you message.
kindly help me with further information. Thank you

Here is one of the LC approaches you can use for analysis of basic, acidic and neutral pesticides:

https://helixchrom.com/applications/bas ... de-column/

Contact me if you have questions.

wandereranalyst wrote:

PhysisGC wrote:
If anyone is interested I have developed a decent acquisition method using MRM.

These compounds do have very high boiling points so I increased the inlet temp to about 360C and that really boosted my transfer onto the column. Then, using the selectivity of MRM I have decent sensitivity for these compounds.

It may not be as good as LC/MS/MS but it does seem to work

Hi!
I'm trying to do simultaneous analysis of neonicotinoids with other pesticides using GCMS. Did you do derivatization for the analysis? What kind of derivative agents did you use in the analysis?
i'd tried to reach you out through your contact in this forum but i couldn't send you message.
kindly help me with further information. Thank you

Hello, sorry you were unable to reach me.

No we did not derivatize any of our neonicotinoid compounds. We are only doing 6 at the moment so i can only speak for those 6. These compounds do not work super well on GC so depending on what your detection limits need to be you may need to use a GC/MS/MS, a single quad just doesn't have enough sensitivity.

What has been the issue you've been having with neonicotinoids?

PhysisGC wrote:
Hello All,

I am supposed to be working on neonicotinoids (imidacloprid, dinotefuran, imidacloprid, thiacloprid, thiamethoxam, clothianidin) by GC/MS but am having trouble with low response. I have also had an issue finding articles detailing methods by GC, most seem to be using an LC/MS.

I have 3 Aginlent 7890s each equipped with 5975C, 5977A, and 7000 MS/MS. I am considering NCI or derivatization but without some guidance its just a shot in the dark.

Does anyone have any experience with these compounds on a GC?

We will eventually need to extract these compounds out of water with a DCM shakeout if anyone has tips on that too.

I had to come up with an identity test for imidacloprid on GC/MS, so I'll be happy to share the methodology:

Sample solvent: Acetonitrile
Oven Program: 50ºC for 2min then ramp to 250ºC at 10ºC/min and hold for 5min then ramp to 325ºC at 10ºC/min and hold for 10min
Run time: 44.5min
Inlet temperature: 325ºC
Injection volume: 1uL
Split flow: 100mL/min
Flow velocity: Helium at 45cm/s
Column: Agilent HP-5ms: 30m x 250um x 0.25um
MSD Transfer line: 335ºC
MS Source: 230ºC
MS Quad: 150ºC
Solvent delay: 5min

My sample concentration was roughly 0.75mg/mL. I never did any quantification of Imidacloprid via GC/MS but it's clear that these parameters provide the ability to detect it. Your mileage may vary on recovery or the ability to quantify, but this might be a good starting point for you. Hopefully this helps.

Here are some chromatograms of the formulation with and without Imidacloprid present so you can see that it does in fact show up:

Here is our imidacloprid standard:


Here is the formulation:


Here is the blank of my formulation and as you can see it is missing the peak at 20.2min where Imidacloprid was shown found.


*Edit for grammar/typo*