Chromatography Forum

Joe wrote


Sorry for the delayed response, I've been giving a talk to the WI about bee keeping this evening.

That's great - thank you. I think sending it out Monday would be the better option, especially as I'm still having issues locating the air leak on my GC-MS after the power failure last weekend. I'm more than happy to pay for the postage, just let me know how to send payment.

I think the diatomaceous earth method has some serious promise, particularly as it has been demonstrated to work on mites smaller than the ones I study. I'm assuming I will have to solvent clean my stainless steel sieves to ensure no contamination?

I'll be solvent extracting my diatomaceous earth with hexane! I also bought some aluminium backed TLC plates today so that I can cut down the area in which my predatory mites can traverse.


I'm more than happy to pay for the postage, just let me know how to send payment.

No worries - pay it forward when you are in the same position later on in life to help someone

I think the diatomaceous earth method has some serious promise, particularly as it has been demonstrated to work on mites smaller than the ones I study. I'm assuming I will have to solvent clean my stainless steel sieves to ensure no contamination?

I really agree - better than the PDMS tubing - yes to the sieve cleaning and wear gloves to prevent any skin sebum contamination at all stages

I'll be solvent extracting my diatomaceous earth with hexane!

Consider also chloroform /methanol as well as hexane .

Hexane is very non polar and will in general only extract non polar compounds. ( think like dissolves like) e.g. hydrocarbons in the main and fatty acid methyl esters just as general examples

Whereas CHCl3/MeOH is much more polar and should extract a wider variety of compounds including non polars plus fatty acids. waxes and wax esters, low and higher mol weight compounds etc much more efficiently

It would be very interesting to compare both extracts in your activity studies - it may lead to some clues

I also bought some aluminium backed TLC plates today so that I can cut down the area in which my predatory mites can traverse.

good thought


I've been giving a talk to the WI about bee keeping this evening.

Interesting, after training with a sugar solution dosed with a target chemical bees have also been used as a volatiles detector commercially for explosives at airports, and screening wine corks for 2,4,6 Trichloro anisole contamination which leads to the "cork taint in" wines

I knew the person involved with this approach and can give you more details if you are interested

.

I'm seriously considering moving into researching insect chemicals after I finish my PhD.

A wide, fascinating and intellectually rewarding field

Do you happen to know which solvents stainless steel is compatible with? I don't want to end up knackering my sieves!

Compatible with all common organic solvents

Is the silica gel compatible with methanol/chloroform? As we discussed previously, I have had bad experiences in dissolving tenax with dichloromethane!

Completely -

I had heard about bees being used in explosive detection, but I had no idea about wine taint. If you have any more information that would be great, it's a really fascinating concept.

I will formulate a reply to that in more detail when I have researched my old contacts over the next few days
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The bees detecting wine taint was a new one for me also, so I would be interested to hear more when you have a chance Ralph.

Peter

Hi Peter and Joe

I have emailed a more detailed reply to you both but an abbreviated version is shown below

I have reached out to my former colleagues to get some more information.

The basic principles are shown in the article and youtube video below

http://www.bbc.co.uk/newsbeat/article/3 ... egal-drugs

https://www.youtube.com/watch?v=_T7d0bze4kM

A former colleague set up a more commercial sophisticated device using the trained bees mounted on a carousel (all bees were treated responsibly and humanely) and optical sensors to detect the bee's tongue response.

The device was proved to work in detecting explosives and taint in cork bark in the factory before processing into wine corks. My memory recalls the taint being 246 TCA in cork

It would seem that the venture was not a commercial success

Regards

Ralph

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Hi Joe

Thank you for letting me know that the PDMS tubing second posting finally successfully arrived

That was my last remaining piece of tubing.

I still prefer Peter's SPE/diatomaceous earth tumbling idea

Looking forward to your updates when you have had time to conduct some experiments - a fascinating study

Regards

Ralph

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Thanks for the update Joe.

Probably a good plan to run a blank - the whole procedure but without any mites.

Methyl acaridate sounds promising for a mite compound, but Google claims it doesn't exist !

Fingers crossed for the TLC bioassay.

Peter

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Hi Joe

With the MW range you are seeing, and what makes sense for a contact cue on a mite's cuticle, evaporating some of the solvent can do no harm at all. Be very cautious about evaporating all of it though.

Excellent result from the blank - I was worrying that a lot of the compounds you are seeing are also on human skin.

Peter

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Hi Joe

The image link is busted, but you will always get some baseline drift with a temperature programme, so unless it obscures peaks I would not worry.

Peter

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Hi Joe,

That blank does look a bit odd, but workable.

To filter out the silica bits you could try a disposable pipette tip with a built in filter, they go down to very small volumes.

Peter