Chromatography Forum

What about your TLC chamber?

I still have this thought about the predators being attracted to volatiles released from the damaged leaf caused by the prey.

How do they arrive (taxi )

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Hi Joe

I wouldn't necessarily worry about not finding alkanes, or anything else on their list and not on yours. All that matters is that you get a positive response in a contact bioassay - then you know that your extract has the active compound(s) no matter how long or short your list of components is.

I might even suggest not doing any analyses until you have the bioassay sorted - but that's the biologist in me talking, not the analytical chemist.

Peter

Sounds good, perhaps for starters use the same time as used for the mites.

I had an infestation of mites on my cherry tree this year but that might be from overwintering eggs. For a new annual broad bean plant where do they come from?

Peter's idea of sorting out the contact bioassay on your extracts first sounds a much more sensible logical approach -

All that matters is that you get a positive response in a contact bioassay - then you know that your extract has the active compound(s) no matter how long or short your list of components is.

I might even suggest not doing any analyses until you have the bioassay sorted -

I have to admit I had lost sight of that

It is a good reminder for me to refocus on what is important . I have allowed myself to diverge and introduced work that can be carried out later. I apologise for that.



Regards

Ralph

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The glass bead bioassay sounds like a good plan.

Dead pigs eh - the things we do for science ! Have fun !!

Peter

Hello,

I must say I haven't had the time to catch up reading the entire tread, so my answer might come to late, or might already been posted.
To prevent silica to be sucked up in the pipet you might try and centrifuge it. if the particals are that small, centrifuging them will get them nice and compact at the bottem of your vial.
The recovery rate of your solvent will be higher and when working gently you will not stir the silica up when pipetting.
We use this technique to dry CH2Cl2 extracts with Na2SO4 and it works really well.

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First of all I must say, this must be the most interesting post on the forum so far. The perfect combination between biology and chemistry. I LOVE IT !!

3. Any Green colour is likely to be chlorophyll

3. That was my initial thought, but it appears to be on the exterior of the mite. This seems a little strange to me.

Might be a really silly thought, but can mites get nauseous?
I can imagine that they are not happy when being solvent washed or tubled in silica for several hours. They might trow up or get diarrhea ? This would explain chlorophyl and the presence of chemicals you would expect to be comming from inside the mite.

I'm not sure if the small amout of supernatant would contain enough analytes to obtain a decent chromatogram?

5-10µl should be enought to have one GC-run. if this is a 200µl vial it should work out just fine.

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Do you have access to dry ice or liquid nitrogen? Would that help to avoid some of the possible vomit issues?

Hi Joe

I like BMU_VMW suggestion of centrifugation.

From the helpful images that you posted it looks like you are getting settlement.

Centrifugation isn't only about the speed - it is also about the rotor size and time

So, the fact that you are getting settlement should mean that it is just a case of running for a lot longer.

I am fairly sure that I have managed to get a pellet out of 20 micron silica suspended in water at the the same speed as you are using and most importantly probably the same rotor diameter.

Interestingly (? haha) you already have 1G acting on it - centrifugation just adds some more Gs to reduce the settlement time. The 1G is how your diatomaceous earth was compacted originally from diatoms floating in the seas but you don't have a few million years

Regards

Ralph

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Hi Joe

It won't be an issue.

Try 1 hour to begin with.

Regards

Ralph

Do you have access to dry ice or liquid nitrogen? Would that help to avoid some of the possible vomit issues?

Hi itspip,

I have access to both. Do you think this rapid freezing method would prevent vomitting? I have heard of carbon dioxide being used to anesthetise insects.

Cheers,

Joe

Joe,

My thoughts are that the liquid nitrogen/dry ice freezing would be quicker and possibly avoid some vomiting. I have heard of different alcohols and some other organics being used to anesthetize insects and small mammals. Not too sure if flash freezing them would help or not.

Good luck,
Philip