Wood vinegar preparation

[GOM]

rb6banjo made some good points.

I think that I covered those off in my previous post - hope so anyway

I forgot to add blanks of

1ml water
1ml water + 300mg salt

Sometimes I found it beneficial to run a vial blank between each sample injection to ensure that the fibre was fully desorbed and that there was no carryover. And/Or using a splitless injection time of 1 minute before venting, leave the fibre in the injection port for another 4 minutes before removal to thoroughly clean it - does that make sense?

Ralph

[EntoJoe]

HI Joe

Saturate it with salt - with salt and vinegar flavour you can't go wrong !

As a fun exercise compare the aroma of unsalted and salted vinegars, that will tell you is your are getting an effect.

Peter

Hi Peter,

Salt 'n' vinegar does happen to be my preffered chrisp choice!

I will certainly compare both the salted and unsalted wood vinegars.

Cheers,

Joe

Salt and vinegar flavoured wood chips - love it - made me smile

As usual you have had some good suggestions - I particularly like the 2 for one effect from neutralisation of the acetic acid.

Since it is just out of curiosity and working with what you have why not try for a start

Headspace sampling for 1 min at ambient temp of

a) 1ml sample
b) 1 ml sample + 300mg of salt
c) 1ml of sample after neutralisation with sodium carbonate or bicarbonate
d) 1 ml water + the amount of sodium carbonate required in c) above as a blank in case it contains adsorbed volatiles

Don't spend too much time on it - you are looking at volatiles in a wide range of concentrations.

It will be an interesting learning curve for you

From experience the volatiles at a lower concentration may require 5 mins sampling at 65°C to capture and identify

Ralph

rb6banjo made some good points.

I think that I covered those off in my previous post - hope so anyway

I forgot to add blanks of

1ml water
1ml water + 300mg salt

Sometimes I found it beneficial to run a vial blank between each sample injection to ensure that the fibre was fully desorbed and that there was no carryover. And/Or using a splitless injection time of 1 minute before venting, leave the fibre in the injection port for another 4 minutes before removal to thoroughly clean it - does that make sense?

Ralph

Hi Ralph,

Thanks for the sample suggestions, I think I will have time to run these tomorrow in between my other jobs.

Your fibre cleaning method makes perfect sense! I already do something very similar as I desorb the fibre in the injection port for 5 minutes, but after 1 minute it purges to the split vent.

What sort of GC conditions should I be using for this? (oven temp, injection port temp, temp ramp, etc)

Cheers,

Joe

Know that the addition of the carbonate salt will titrate all of the acidic species (carboxylic acids, phenols, maybe thiols, etc.) in the solution so you likely won't see them anymore. Some things may also react at high pH - ester hydrolysis for instance. My philosophy on this sort of thing is do as little "harm" to the sample as possible until you realize that conventional means are not going to get you where you want to go. I would analyze the wood vinegar straight at first and then see what I get. If you find that the acidic species are of little interest, then add the carbonate salt to go after the neutral species and the basic species. A salt like sodium chloride is the best way to create high ionic strength yet not change the reactivity of the medium a great deal.

Hi rb6banjo,

I agree with your philosophy of doing no harm, so will progress using Ralph's suggestion above.

Cheers,

Joe

[GOM]

Your technique sounds good

For your column HP5

Initial temp 40°C hold for 1 min
Final temp 260°C - you can go higher on this phase but probably won't need it
Ramp 3°C/min
Injection temp 270°C - max temp for your fibre but double check here
https://www.sigmaaldrich.com/content/da ... 794123.pdf

These are only suggestions but should give you a starting point for exploring what is just a curiosity exercise

Others may have a better suggestion for the temperatures

Ralph

[BMU_VMW]

definitly make sure you run a blank when using salt.
For my odor analysis (0.05ng/l for some of the analyts ) I bake the NaCl at 600°C for a few hours, if not I get some extra peaks for free
Don't know if it will make a lot of difference for your test, since you concentrations will be a lot higher.

btw: thanks anamariboyes for that Tip.

[EntoJoe]

Your technique sounds good

For your column HP5

Initial temp 40°C hold for 1 min
Final temp 260°C - you can go higher on this phase but probably won't need it
Ramp 3°C/min
Injection temp 270°C - max temp for your fibre but double check here
https://www.sigmaaldrich.com/content/da ... 794123.pdf

These are only suggestions but should give you a starting point for exploring what is just a curiosity exercise

Others may have a better suggestion for the temperatures

Ralph

Hi Ralph,

Thanks for this advice, it seems to be working well. I am going to go through the data tomorrow, but I have a chromatogram at least!

The only issues I have now is that all of my Hamilton glass syringes smell of wood vinegar and cleaning with chloroform:methanol doesn't appear to make any difference. Do you have any tips on how to clean the syringes of contaminants?

Cheers,

Joe

definitly make sure you run a blank when using salt.
For my odor analysis (0.05ng/l for some of the analyts ) I bake the NaCl at 600°C for a few hours, if not I get some extra peaks for free
Don't know if it will make a lot of difference for your test, since you concentrations will be a lot higher.

btw: thanks anamariboyes for that Tip.

Hi BMU_VMW,

Thanks for the tip, I managed to do that before running my sample!

Cheers,

Joe

[GOM]

Try soaking in bicarbonate solution

[EntoJoe]

Try soaking in bicarbonate solution

Hi Ralph,

I assume this is a bicarbonate and water solution?

Cheers,

Joe

[GOM]

Hi Joe

Yes

Regards

Ralph

[EntoJoe]

Hi Joe

Yes

Regards

Ralph

Hi Ralph,

Thanks for the suggestion, however it didn't seem to help!

Cheers,

Joe

[GOM]

Hmmm

Is the odour acetic acid (vinegar)?

Is this a glass syringe with a steel plunger - no plastic involved?

Try 0.05M NaOH aqueous solution soaking

As an aside, if you can smell it then it must be volatile at room temp and therefore must eventually dissipate. If PTFE or any other plastic is involved it will take longer.

As a further aside

From experience any plastics( polymers) are essentially to be regarded as a solid liquid and you can get partitioning of an odour into them, which will take a long time to desorb.

I once had a 10uL Hamilton glass syringe that still smelt of a thiol after 2 years! But that is unusual

If it is acetic acid this shouldn't be a problem



Regards

Ralph

[EntoJoe]

Hmmm

Is the odour acetic acid (vinegar)?

Is this a glass syringe with a steel plunger - no plastic involved?

Try 0.05M NaOH aqueous solution soaking

As an aside, if you can smell it then it must be volatile at room temp and therefore must eventually dissipate. If PTFE or any other plastic is involved it will take longer.

As a further aside

From experience any plastics( polymers) are essentially to be regarded as a solid liquid and you can get partitioning of an odour into them, which will take a long time to desorb.

I once had a 10uL Hamilton glass syringe that still smelt of a thiol after 2 years! But that is unusual

If it is acetic acid this shouldn't be a problem

Regards

Ralph

Hi Ralph,

The smell isn't actually vinegar-y, rather more of a smokey smell. It's really quite unpleasant haha!

All of my syringes and plungers are stainless steel, although there are PTFE sealing rings.

I'm not sure I have two years to wait for this to dissipate naturally

Cheers,

Joe

[GOM]

aaah!

So, just to clarify

The odour isn't in fact vinegar?
The odour isn't wood vinegar?
The odour is smokey
You have plastic in your syringe

Regards

Ralph

[EntoJoe]

aaah!

So, just to clarify

The odour isn't in fact vinegar?
The odour isn't wood vinegar?
The odour is smokey
You have plastic in your syringe

Regards

Ralph

The odour originates from the wood vinegar, but the wood vinegar itself doesn't smell of vinegar. It has a really smokey smell associated with it.

There is minimal amounts of plastic, and it is the metal itself that smells. I have dismantled the syringes to clean, so smelt each part like a lunatic!

Cheers,

Joe

[GOM]

Interesting.

Sulphur containing molecules can latch onto stainless steel.

Phenolics may be source of the odour

https://c.ymcdn.com/sites/echocommunity ... inegar.pdf

Can't think of anything useful to help clean your syringe - elevated temperature or vacuum may help to increase the evaporation of the volatiles

Might be interesting to take an SPME headspace of the syringe plunger

Regards

Ralph

[BMU_VMW]

if it is just the metal parts that are smelling, why not simply put them in an oven at e.g; 150°C ?