Chromatography Forum

Hi joe

For the development of the artificial diet I think you need to concentrate on the short range attractant/trail compound(s), and especially on the contact cue. You will be giving the predators their food, so they don't need to go searching for it.

Reducing contact time in the extractions is a good idea - the easiest way to do it is to plug the stem of a glass Pasteur pipette with a tiny bit of packed glass wool, put the mites in the body of the pipette, and then percolate solvent through and catch the drips- like making filter coffee. You might see that the first few drops run clear and then the green colour appears.

Peter

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The peaks from a percolated sample extract being smaller might actually be a GOOD sign - it points to some selectivity in the extraction. You don't need much of a peak to pull a decent spectrum off it.

I've just checked that silica rubbing paper - it certainly worked for them.

Peter

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Hi Joe

Long. medium and short range - interesting.

Are the long/medium range resulting from volatiles released by the plant by damage to the plant membrane?

I recall from somewhere that when police dogs are tracking a suspect across grass that they are actually tracking the hexenal released from damage to the grass leaves. It is the odour associated with new mown grass

I have definitely found biological activity in the hexane solvent extract previously, but I need to find a way to optimise this extraction methods to minimise leeching of internal compounds. I think this will require freeze killing the mites, air drying them under desiccation for 48 hours and then solvent extracting them using a hexane:chloroform mixture for 2 minutes before evaporating to dryness and re-suspending in solvent.

I am concerned that this procedure will remove short range volatiles

Anhydrous Na2SO4 is commonly used to remove water - often from organic solvents

Regards

Ralph

Let me know if the tubing arrives OK -if not I can post some more out

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Hi Joe

Keep it as simple as you can - do the silica contact extraction and then extract the silica. The flash chromatography is a sample clean up that you might not need, and if you do not do the flash chromatography then there is probably no need to dry the extract. The less you do the less there is to go wrong, or to introduce variability.

Peter

Hi Joe

Interesting abstract - yes please send the pdf.

It confirms Peter's suggestion of using SPE or diatomaceous earth.

The silicaceous diatoms have a huge surface area



A purified version used as a GC stationary phase support for packed columns used to be sold under the name Chromosorb (AW - =acid washed)

http://www.sigmaaldrich.com/catalog/pro ... &region=GB

For your purposes 60-80 mesh particle size should be fine

Regards

Ralph

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Hi Joe

That sounds sensible

Regards

Ralph

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Hi Joe

The description high grade/purity sounds good, as does your particle (mesh) size choice.

Peter's idea has legs!

Regards

Ralph

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Hi Joe

OK thanks for the update - the tubing should have arrived by now

i will post out my remaining tubing sample tomorrow under recorded/signed for next day delivery

Would I be better mailing the tubing out next Monday rather than risking it arriving over the weekend at your University address?

Let's hope that delivery works

The diatomaceous earth idea sounds really promising ( better than the PDMS tubing idea) , especially with being able to sieve it to remove the mites

The more I think about it, the more I prefer the diatomaceous earth approach over the PDMS approach

You can solvent extract the diatomaceous earth ( best way) not forgetting a solvent extraction control blank or thermally desorb it - the crudest way of thermal desorption would be as in the presentation that I sent you using Tenax



Regards

Ralph

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