Sciencemadness Discussion Board

The Sciencemadness TLC Apparatus Challenge

Metacelsus - 27-4-2018 at 04:32

Introduction:
For many home scientists, TLC is the analytical method of choice for mixtures of organic compounds. Even in professional labs like the one I work in, TLC is used every day. However, often the results of TLC are annoyingly variable, due to lack of control over spotting and elution. (Just today, a thread was posted complaining about this.) Automated TLC systems exist, but these are prohibitively expensive for a home lab (and even for many professional labs). The goal of this challenge is to improve TLC by making devices to decrease the variability. The challenge is designed to be difficult but not impossible given a few months of time.

Rules:
The prize money goes to whoever submits an entry first, with sufficient proof that the criteria have been met for the prize. I am the final judge of such proof.
Device schematics, pictures, source code (if applicable, including .stl files for any 3D printed components), and statistical data must be publicly available.
Detailed instructions must be provided on device construction and use.
All challenge submissions will have a CC-BY-SA 4.0 license.

After an entry is submitted, there will be a one-week public comment period before the award becomes official.
Even after the main prize in a category has been awarded, users can still submit entries for bonus prizes.

Prize money will be sent via PayPal within one month of official award announcement. Alternate payment methods may be allowed upon request, but there are no guarantees.
The challenge closes September 1. No entries will be considered after then.

Note: It is quite likely that the prize money will be less than the cost of creating the devices, but remember that you will still have the device for your own use after you finish building it for the challenge. A working device is its own reward. Of course, other users are free to contribute additional money to the prize pool if they want.

Category 1: Spotting
Make a device to automatically spot a fixed volume of liquid (in the range of 1 to 5 µL) onto a TLC plate, with coefficient of variation less than 10% over at least 20 spots. Prize: $50
Note: Other than delivering a precise volume, there are no restrictions on the device. It could be a simple handheld mechanical device, or something more complicated.

Bonus: Have the amount of liquid spotted be adjustable by the user: $10
Bonus: Be able to spot multiple (at least 5) spots a fixed distance apart on the same plate: $10
Bonus: Quantify spot areas and retention factors using open-source image analysis software: $5

Category 2: Elution
Make a device to automatically elute TLC plates and stop elution when complete. Elution must be even (no wavy solvent fronts allowed!) The device must be tested with at least five plates, each of which having at least three spots. Coefficient of variation in retention factors must be less than 10%. Prize: $50

Bonus: Make your own TLC plates and successfully demonstrate their use in your system: $20
Bonus: Automatically apply stain to plates after elution is complete: $5

This thread is for discussion of the challenge. Submissions should be posted in their own threads. I would appreciate it if a mod could sticky this until the challenge is over.

Edit: Decreased upper volume range from 10 to 5 µL, since 10 µL is too much to spot on a TLC plate.

[Edited on 4-27-2018 by Metacelsus]

Texium - 27-4-2018 at 04:45

Sounds like an interesting challenge! It solves a problem that I didn't know existed, being as I've always spotted plates by hand, even at work, and I suppose I've just gotten used to preparing and eluting my plates very carefully. Reading how you describe the issue though, it does sound like it would be a convenient device to have.

Ubya - 27-4-2018 at 05:11

and here i am thinking about recycling used TLC plates taken from the university Organic chemistry lab hahahahaha
let's see what we can invent:D

Metacelsus - 27-4-2018 at 06:02

Quote: Originally posted by Texium (zts16)  
Sounds like an interesting challenge! It solves a problem that I didn't know existed, being as I've always spotted plates by hand, even at work, and I suppose I've just gotten used to preparing and eluting my plates very carefully. Reading how you describe the issue though, it does sound like it would be a convenient device to have.


I also do manual TLC a lot, and I have gotten to the point where it's generally pretty reliable for qualitative work. However, spotting consistent volumes is still a challenge. For example: is fraction 1 from a column more concentrated than fraction 2, or did I just spot a greater volume of fraction 1?

Dr.Bob - 27-4-2018 at 07:56

I had programmed a liquid handler robot to spot TLCs years ago, and it worked pretty well until that model was obsolete, but not a trivial issue. One hint is that if you put the TLC plate on a piece of open cell foam before spotting it, that makes any spotting system work better as if you press too hard by mistake the plate moves down some, thus avoiding breaking the sorbant layer. I still like really fine glass capillaries, but they are quite fragile and require a delicate touch. Small (20 ul) plastic pipette tips like for Gilson pipettors might also work. And remember that quantifying anything by TLC is nearly impossible due to variable UV absorption of compounds. Good luck.

Best thing ever for good TLC, a kitchen timer that you set to 4 or 5 (or X) minutes when you drop the plate in. That way they are all done the same time, which makes them much more reproducible.

[Edited on 27-4-2018 by Dr.Bob]

Vosoryx - 28-4-2018 at 18:25

This is a very interesting challenge indeed.
I have a lot of experience/tools with electronics, as well as a 3d printer. Come summertime, I might give this a shot... But I also might not. I will let you know if/when I do. It all depends on how much free time I end up having.... we'll see.

AvBaeyer - 28-4-2018 at 18:33

In terms of uniform spotting volumes, there is a commercial product called "Drummond Microcaps" which come in various volumes from 1 - 10 microliters that I know of. These are uniform capillaries which work very well. I use these all the time an though they are "disposable" they can easily be cleaned and reused over and over. I have been using a pack of 100 2 microliter caps for several years now. The 2 microliter caps are ideal for nearly all tlc spotting applications. I found mine on ebay at a reasonable price.

By the way, this is a very challenging challenge.

AvB

Doc B - 28-4-2018 at 18:54

Wouldn't a handheld multi channel micropipett (see link below), with low volume tips, set between 1-5µL deliver all the requirements of category 1?

https://www.thermofisher.com/au/en/home/life-science/lab-pla...

Metacelsus - 29-4-2018 at 07:30

Quote: Originally posted by AvBaeyer  
In terms of uniform spotting volumes, there is a commercial product called "Drummond Microcaps" which come in various volumes from 1 - 10 microliters that I know of. These are uniform capillaries which work very well. I use these all the time an though they are "disposable" they can easily be cleaned and reused over and over. I have been using a pack of 100 2 microliter caps for several years now. The 2 microliter caps are ideal for nearly all tlc spotting applications. I found mine on ebay at a reasonable price.


I didn't know these existed, but now I want to buy some. They look very useful for TLC, and if someone could make them, then that would certainly fulfill the challenge.
Quote: Originally posted by Doc B  
Wouldn't a handheld multi channel micropipett (see link below), with low volume tips, set between 1-5µL deliver all the requirements of category 1?

https://www.thermofisher.com/au/en/home/life-science/lab-pla...


Yes it would - provided you make it yourself.

[Edited on 4-29-2018 by Metacelsus]

weilawei - 30-4-2018 at 14:49

Would something rigged out of an inkjet printer count? I wouldn't build the print head myself, but perhaps custom templates to print off rows of spots on TLC plates plus modified reservoirs for easy loading might work.

Metacelsus - 1-5-2018 at 05:46

Yes it would. I suggest you take a look at these relevant papers:

https://pubs.acs.org/doi/abs/10.1021/ac902945t
https://www.sciencedirect.com/science/article/pii/S002196731...

Reboot - 1-5-2018 at 16:00

Neat!

Here's the first cited article (using printers and scanners for TLC.)

Attachment: morlock2010.pdf (1.6MB)
This file has been downloaded 1029 times

Dr.Bob - 2-5-2018 at 09:10

I am remembering when we used to make our own TLC spotters in the undergraduate research lab by heating a pipette in the middle and having two people grab the ends and run apart. We would get a 20-40 foot long capillary that we could break off 100+ spotters from. Now I just use the ones made from commercial glass capillary tubing, the are very fine, but spot tiny spots with ease.

The best simple TLC spotting technique I have seen is to just use a pencil to mark a line 1/4" from the bottom, then put a pencil mark below that line spliting it in half, then mark the center of each of those spots, until the bottom of the plate looks like this: (with the lines about 1/8" apart or more. This would be a 2" (50 mm) wide plate.

______________________________________
| | | | | | | | | | | | | | | | |

Then spot your material in each cell, so it looks like this: Each spot must be within the lines, the smaller the better.

_______________________________________
| o | o | o | o | o | o | o | o | o | o | o | o | o | o |

If you then put the plate in a TLC chamber (or beaker with a watch glass on top) with a piece of filter paper on the bottom to help keep it from sliding on the bottom, and 1/16" deep solvent in it, let it run 4-8 minutes, you will get a decent result.

Mush - 3-9-2019 at 11:44

DIGITALLY-ENHANCE THIN LAYER CHROMATOGRAPHY:
DEVELOP A NEW MEHOD OF TERBUTALINE SULPHATE IN BULK
DRUG

ABSTRACT
Digitally-Enhanced Thin-Layer Chromatography is An Inexpensive,
New Technique for Qualitative and Quantitative Analysis. Thin-layer
chromatography (TLC) is a widely used method for qualitative
analysis to determine the number of components in a mixture, to
determine the identity of two substances, or to monitor the progress of
a reaction. The more accurate high-performance TLC (HPTLC) is
better suited for quantitative analysis. If digital photography is
combined with regular TLC, it can perform highly improved. An
apparatus for digital imaging of TLC plates was prepared. The
equipment was made from wooden sheet. It consisted of three main
parts: A TLC development chamber, image acquisition cabinet and
image analysis software installed on a personal computer.


A Toolkit to Quantify Target Compounds in Thin-Layer-Chromatography Experiments
J. Chem. Educ.201895122191-2196

Abstract

Thin-layer chromatography (TLC) is one of the basic analytical procedures in chemistry and allows the demonstration of various chemical principles in an educational setting. An often-overlooked aspect of TLC is the capability to quantify isolated target compounds in an unknown sample. Here, we present a suitable route to implement quantitative analysis in a lesson plan. We provide both a stand-alone software and an online webapp that allow students to obtain quantitative information from a developed TLC plate and present two suitable experiments, namely, the absorbance-based quantification of the colorant Sudan IV and the fluorescence-based quantification of rhodamine 6G, a fluorophore widely used in biotechnology. Students conduct TLC experiments following established protocols, take pictures of their TLC plates with mobile phones, and subsequently quantify the different compounds in the separate bands they observe.


Attachment: acs.jchemed.8b00144.pdf (3.4MB)
This file has been downloaded 768 times

Attachment: article_wjpps_1496231913_Digitally-Enhanced Thin-Layer Chromatography.pdf (375kB)
This file has been downloaded 821 times