Micro screening method for blends/accords

FragOz

Active member
Jan 8, 2022
Use case: testing multiple chemicals against each other or a pre-mix to find good blends or potential accords

Material

0,5 ml vials | pipettes | styrofoam board | packaging tape | ruler | marker | coffeefilter | scissors | tweezer | AC's you want to test. The vials are used in microbiology and can be cheaply bought on Aliexpress or the like.

Procedure
Preparation:
Think of the amount of AC's you want to test as a table, useful formats can be eg. 5 * 10 or 7 * 7. Draw the outlines of the table on the styrofoam, using 3 cm (1.2") distance between the points. Cut the styrofoam with 4-5 cm (1.6-2") margin to the table outline. Tape the outer sides with the packaging tape so no styrofoam 'bubbles' can come off. Now draw the full table and mark columns like in Excel, A-Z for columns and numbers for rows. Label the vials according to their cell, like 'A1' or 'C5'. Push them at the line crossings in the styrofoam at the right position. You can reuse the styrofoam board for later experiments. Cut tiny pointy wedges from the coffeefilter with a length of about 75% of the heigth of the vials.

Testing: pre-dilute the AC's in order to have roughly the same odor strength (or use more drops later on).
You will need rows * colums disposable pipettes (or glass if you work with that). Place 1 drop of each chemical in each vial and closely keep track of what you are doing in a notebook. You can fill 1 row or 1 column using only 1 pipette. You'll end up with only 2 (or more) drops of chemicals per vial. It is advised to pre-dilute to 10% but not necessary for this procedure. Wait for an hour and check the vials for balance in odor strength, otherwise adjust.
IMPORTANT: leave for 24 hrs at room temperature. These vials are to small to properly mix, so the AC's in it will mix by natural diffusion. Pre-diluting in DPG will enhance this process. Do not add AC's after the insertion of the coffeefilter wedges (next step). They'll stick to the wedge and will not mix.

Next use the tweezers to drop a coffeefilter wedge in each vial. Do not get your tweezers contaminated! Close the vial and gently bump it to your worktable surface to get the wedge into the mixture if necessary. The wedges will absorb the mixture and allow for enhanced evaporation within the vial. Leave for an hour at room temperature and you are ready to smell for the first time. Make notes and smell another time (using the guidelines for proper smelling elsewhere on BN). Coffeefilter is advised because it has a very open structure, allowing for rapid liquid movement and evaporation.
IMPORTANT: If you plan to add more AC's to the vials over time then skip the wedges. The use of the wedges allows for good smelling with only a minimum amount of AC's used but they are not absolutely essential.

Pro's: you can now easily test series of AC's against each other or a pre-mix of your choice. If you want you can test with less AC's but eg. in different concentrations. The materials are cheap and mostly easily available. Using only 1 or a few drops of AC-solution is also quite cheap, making this a very cost effective method of screening. You can keep the vials for repeated smelling and eventually add new AC's. In that case do not add the paper wedges, they are not absolutely essential as mentioned.

Con's: you will have to order the vials and they are quite small to handle. They exist in other sizes as well, like 1.5 ml. This method uses disposable materials, but in quite an effective way. The method is less useful for viscous materials. This method will give an indication of potentially useful combinations, which can be selected for further investigation and finetuning. The method can also be used for Jean Carles style finetuning of proportions in a second step, but you can also use your own preferred method.

Microscreening.jpg
Picture: in the background you can see the prepared sytrofoamboard with tape-lined edges and the table with vials inserted. A shows the unbleached coffeefilter of which the wedges are cut, B shows dropping of the wedges into the vials using tweezers and C shows how the wedge absorbs the liquid in the vial, working as evaporation enhancer.

Tube.jpg
Tip: use a tube as a smelling aid to create distance between your hands and your nose. For 0,5 ml vials a ballpen casing has a good chance to fit.

I hope you can use the suggested method to your advantage!
 
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Big L

Well-known member
Nov 23, 2019
I appreciate your systematic approach and like your style!

Still, I am asking myself if it's not a bit over complected rather than efficient.

If all you are after are "rough indication of potentially useful combinations" careful use of paper smelling strips (using accurate pipets to ensure exact volumes of prediluted stock solutions, etc.) might be all you need.

A possible advantage I cam imagine would be if you can close the vails and use them as refrence for a long time (days/weeks/months) without the odor profile changing much.

What in your experience is the main benefit of using this method over the standard smelling strips?
 

FragOz

Active member
Jan 8, 2022
Hi Big L, thanks for your kind compliments!

And a good question indeed. With a 'rough indication' I mean you're using drops which is not the most accurate way of working. You can use this method like a dropwise Jean Carles method however, which adds some accuracy. You made me think and I changed 'rough indication' to 'indication' in the original post.

There are 3 benefits IMHO:
1. being able to close and keep the vials for days to weeks,
2. being able to add more AC's over time and
3. have better mixing than on a smelling strip.

Ad 1. The key here is to find components that match as a first step. I need to mention that I like to work with synthetics, which are really suited for this method. The second step is finding the right proportions for an accord, which requires more precision and a scale. Many people here may like to use their own preferred methods for this step. So for me it is a 2 step process: 1. screening and 2. finetune potential matches. The presented procedure works a lot faster than weighing and as you noted the biggest benefit is that you can keep the mixtures, even for several weeks. This kind of vials is made for laboratory use in microbiology, they close very well and can even withstand centrifuging at 15.000 RPM.

Ad 2. Another important benefit is that you can easily add new AC's with minimal use of disposables. This is for me also an important benefit of the presented method. This is especially useful if you want to add the same AC to multiple rows/columns of vials, eg Hedione or a Salicylate to test which one (or combined) is the best booster for the mixture. In this case you should leave the paper wedges out, but to my experience these are not always essential for good smelling. I updated the post accordingly.

Ad 3. The last benefit comes from my experience that the odor of freshly mixed AC's can change after they have really mixed well, often the mixture becomes somewhat smoother so to say after 24 hrs in a vial. Putting them on a smelling strip does not allow for this, as the solvent probably evaporates too quickly.

Of course smelling strips are fine, its up to the user to decide which method fits best for a particular case. I certainly agree with you that things should not get overcomplicated!
 
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Big L

Well-known member
Nov 23, 2019
Thank you for sharing and further explaining your method. I totally get the benefit of keeping a mixture for a while, evaluating and comparing with other mixes over time.

Following are a few thoughts and suggestions off the top of my head:

With a 'rough indication' I mean you're using drops which is not the most accurate way of working.
If you are already going for a scientific lab-like technique, why stop at the microcentrifuge tubes? You can easily get very high accuracy by working with prediluted stock solutions prepared to a set value of mg/ml (or ug/ml) and a micropipette. (I am assuming this is straightforward enough, let me know if you would like me to elaborate on it.)

Ad 3. The last benefit comes from my experience that the odor of freshly mixed AC's can change after they have really mixed well, often the mixture becomes somewhat smoother so to say after 24 hrs in a vial. Putting them on a smelling strip does not allow for this, as the solvent probably evaporates too quickly.
I would hate to get to a religious-like argument over that, but as a side note, I think that for the most part (excluding the cases where there are obvious, known reactions), when working with ACs, they will not change their odor over time, or by mixing. What will change are the fatigue of your nose and the contamination of your working area. There are also benefits to allowing the solvent to completely evaporate before evaluating, for a more accurate perception of the odor profile.

Regardless of how long you would like to wait, etc., my suggestion is to skip the coffee filters. When you are ready to evaluate a mixture in one of the tubes, accurately pipette out a standard amount, say 20uL (20 microliters), put it on a strip, let it dry completely, and evaluate using recommended techniques (overtime, hopefully outside or in a well-vantilated area, etc.).

This will allow you a very accurate comparison between different formulas and make your formulated vails last for many such evaluations rounds.
 

mnitabach

Well-known member
Nov 13, 2020
If you are already going for a scientific lab-like technique, why stop at the microcentrifuge tubes? You can easily get very high accuracy by working with prediluted stock solutions prepared to a set value of mg/ml (or ug/ml) and a micropipette. (I am assuming this is straightforward enough, let me know if you would like me to elaborate on it.)

I do all of my blending experiments with w/v prediluted stocks & micropipettors, just like I used to run recombinant DNA enzymatic reactions as a grad student & post-doc!
 

FragOz

Active member
Jan 8, 2022
Thank you for sharing and further explaining your method. I totally get the benefit of keeping a mixture for a while, evaluating and comparing with other mixes over time.

Following are a few thoughts and suggestions off the top of my head:


If you are already going for a scientific lab-like technique, why stop at the microcentrifuge tubes? You can easily get very high accuracy by working with prediluted stock solutions prepared to a set value of mg/ml (or ug/ml) and a micropipette. (I am assuming this is straightforward enough, let me know if you would like me to elaborate on it.)


I would hate to get to a religious-like argument over that, but as a side note, I think that for the most part (excluding the cases where there are obvious, known reactions), when working with ACs, they will not change their odor over time, or by mixing. What will change are the fatigue of your nose and the contamination of your working area. There are also benefits to allowing the solvent to completely evaporate before evaluating, for a more accurate perception of the odor profile.

Regardless of how long you would like to wait, etc., my suggestion is to skip the coffee filters. When you are ready to evaluate a mixture in one of the tubes, accurately pipette out a standard amount, say 20uL (20 microliters), put it on a strip, let it dry completely, and evaluate using recommended techniques (overtime, hopefully outside or in a well-vantilated area, etc.).

This will allow you a very accurate comparison between different formulas and make your formulated vails last for many such evaluations rounds.
You are right, accuracy can certainly be extended. Remembering from college time (long time ago) micropipettes were instruments priced above USD 500, so I simply never thought about buying one now. But I am surprised to see that the prices have come down. The tips are readily available, so all together that is an interesting idea!

With respect to the mixing: it is indeed very valuable to experience the dry down over time, something that can't be done with the method I presented. A micropipette is a useful tool in this step, so another argument to go look for one :) And then the filters are not useful anymore.

Thanks for sharing your insights, I am happy to see that a useful thread is growing here!
 

Big L

Well-known member
Nov 23, 2019
I do all of my blending experiments with w/v prediluted stocks & micropipettors, just like I used to run recombinant DNA enzymatic reactions as a grad student & post-doc!
Same here, it is very convenient :geek:🤘
(Writing things like " made 10% stocks in EtOH & spotted 100 ul on the smelling strip" gave you away a long time ago...)
 

FragOz

Active member
Jan 8, 2022
I do all of my blending experiments with w/v prediluted stocks & micropipettors, just like I used to run recombinant DNA enzymatic reactions as a grad student & post-doc!
You're right, this works fine and you are still in that business so that's an obvious choice. (y):)
 

Big L

Well-known member
Nov 23, 2019
Thanks for sharing your insights, I am happy to see that a useful thread is growing here!
Same here #2!

I totally recommend the micropipettes, and as you noticed, if you don't go for one of the top lab brands, it's defiantly not going to be the expensive part of your hobby.
 

mnitabach

Well-known member
Nov 13, 2020
Same here #2!

I totally recommend the micropipettes, and as you noticed, if you don't go for one of the top lab brands, it's defiantly not going to be the expensive part of your hobby.

You can buy very cheap micropipettes (like 1/10 the price of genuine Eppendorf or Gilson) on Amazon. For perfumery experiments, you don't really need accuracy, just precision, and these seem fine. I'm sure they won't last nearly as long as the "real" lab quality stuff, but who cares. It's SOOO much faster to assemble complex experiments like this than with a scale. Knock-off tips on Amazon are also ridiculously cheaper than the real stuff & fine for perfumery (not for a forensic DNA lab tho, eg).
 

FragOz

Active member
Jan 8, 2022
Actually this thread was started to spot the molecular biologists on Basenotes - glad to have found you guys! :ROFLMAO::ROFLMAO:

Have you already spotted this nice upcoming piece of molecular literature? On pre-order now.
 

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FragOz

Active member
Jan 8, 2022
You can buy very cheap micropipettes (like 1/10 the price of genuine Eppendorf or Gilson) on Amazon. For perfumery experiments, you don't really need accuracy, just precision, and these seem fine. I'm sure they won't last nearly as long as the "real" lab quality stuff, but who cares. It's SOOO much faster to assemble complex experiments like this than with a scale. Knock-off tips on Amazon are also ridiculously cheaper than the real stuff & fine for perfumery (not for a forensic DNA lab tho, eg).
Ok now I am totally convinced! I'll go look for one!
 

mnitabach

Well-known member
Nov 13, 2020
Ok now I am totally convinced! I'll go look for one!

These were each less than $50, and the yellow disposable tips for 1-20 & 20-200 are just a few cents each (I use a shitton). The tips for the 200-1000 are I think more expensive (they certainly have a lot more plastic), but I use vastly fewer (pretty much only for distributing dilution alcohol in test vials).

PXL_20220113_213952349~2.jpg

I do all my trials in 2-3 ml sprayers (about $0.25 each), so I can spray on smelling strips and on skin:

PXL_20220113_214629680~2.jpg

This all costs money, but I value my time at a pretty high hourly rate, so it's much cheaper for me to do things this way.

And anyway, I'm sure you can back-of-the-envelope, but doing all my experimenting in predilution this way, in addition to saving enormous amounts of time per trial, saves enormous amounts of material (money) AND takes one away from the "witches brew" method of composition. IMO this "witches brew" business is disastrous for getting good at perfumery because (1) it means you almost never think about what to remove from a failed composition, just what to add to "fix" it & (2) it means that you are making vastly fewer different blends over time & thus learning perfumery vastly more slowly. IMO the only real way to learn is to iterate as many experimental blends as you possibly can, without being inhibited by fear of failure or of "ruining" anything or throwing blends out.
 

FragOz

Active member
Jan 8, 2022
These were each less than $50, and the yellow disposable tips for 1-20 & 20-200 are just a few cents each (I use a shitton). The tips for the 200-1000 are I think more expensive (they certainly have a lot more plastic), but I use vastly fewer (pretty much only for distributing dilution alcohol in test vials).
Very interesting, thank you for showing the details. Understand what you say, time is precious and this looks like a very efficient way of working. Very useful 👊👍
 

Casper_grassy

Well-known member
May 5, 2020
Just a few questions maybe someone can help, I’ve never used a micropipette before and have been interested in one. Really just the 2-20 ul, but my question is 1. How does one set the pipette to correlate with weighing in grams because uL is volume

Also because the tips at least for 2-20, does it work fine with thicker materials like suederal, aurantiol etc? Even diluted they are still pretty viscous
 
Dec 2, 2021
You can look up the Specific Gravity for each material at some place like TGSC then divide by that number to convert from weight to volume. If the material is diluted you get to do even more annoying calculations. It's more a tool for making many repeated transfers of the same volume to a lot of vials than for everyday use where you would use a scale.

 
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mnitabach

Well-known member
Nov 13, 2020
Just a few questions maybe someone can help, I’ve never used a micropipette before and have been interested in one. Really just the 2-20 ul, but my question is 1. How does one set the pipette to correlate with weighing in grams because uL is volume

Also because the tips at least for 2-20, does it work fine with thicker materials like suederal, aurantiol etc? Even diluted they are still pretty viscous

You need to make weight-by-volume (w/v) dilution stocks of your materials. Like a "10% w/v" stock of lyral means 1g lyral per 10ml of stock, which you make by adding 1g of lyral to a vessel & adding diluent to bring the final total volume to 10ml. Then by measuring a volume of this stock, you are measuring a weight of the material. And yes, it is more difficult to pipette more viscous liquids. You will get experience by doing.
 

Casper_grassy

Well-known member
May 5, 2020
You need to make weight-by-volume (w/v) dilution stocks of your materials. Like a "10% w/v" stock of lyral means 1g lyral per 10ml of stock, which you make by adding 1g of lyral to a vessel & adding diluent to bring the final total volume to 10ml. Then by measuring a volume of this stock, you are measuring a weight of the material. And yes, it is more difficult to pipette more viscous liquids. You will get experience by doing.
Ohh that’s simple enough. Thanks I think i’m gonna buy one.

Maybe i’ll buy different color bottles for the stock I make lol don’t wanna go messing everything up
 

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