05-03-02 04:12
No 304428
After going through the search engine and rhod's site, I realized there was no easy faq or work up for TLC, even ghetto variety.
What I'd like to request is that folks list their experience/research/cites for TLC workup. Please post commentary elsewhere and we'll keep this on track. I'll assemble all of this into an easy to use guide for refinement and experimentation. Here's the suggested format.
Target Compound:
Media: (paper/cellulose/silica/etc. )
Elution Solvents: (EtAc,MeOH etc w/ ratios)
Visualization: reageants if any or U.V.
rF: for target compounds and any secondaries or unreacted
secondary/precursor compounds
Infinite Radiant Light - THKRA
(Moderator)
05-03-02 11:55
No 304549
After going through the search engine and rhod's site, I realized there was no easy faq or work up for TLC, even ghetto variety.
This is nonsense, see ../rhodium
/psilo-t
Use of Ethanol-Water Adsorbent Slurries in Coating of Thin-Layer Chromatographic Plates
An Inexpensive Thin-Layer Chromatographic Spreader
Devices for Thin-Layer Chromatography
Transfer Tool for Thin-Layer Chromatography
Technic and Enclosure for Rapid Chromatographic Spotting
Technic for Separation and Solution of Zones in Thin Layer Chromatography
Desiccation Box for Thin-Layer Chromatographic Plates
From equipment fabrication to simple how to's, it's in that post 
Further information not available on Rhod's page and that post would be welcome 
(Pioneer Researcher)
05-03-02 17:53
No 304596
There's litlle information about TLC in the Hive, Osmium and other bee (Ritter?) posted rf of iso, ketone and glycol with hexane:ethyl acetate and toluene:ethyl acetate system, that are very good for this purpose. Methanol:NH3 ,10:1 or so is also good for amines, but we have not an extensive work showing how to make TLC and some common rf of interesting products. Anyway the topic has been discussed, the use of UV plates and the appropiate lengthwave etc...
(Chief Bee)
05-03-02 18:14
No 304601
(Rated as: excellent)
Here is the TLC chapter from Zubrick, in DejaVu format: ../rhodium /equipme
You need the DejaVu browser plugin to be able to read it: http://www.lizardtech.com/includes/downl
(Hive Bee)
05-03-02 19:17
No 304608
No lugh, your full of shit... I have used the search engine, if you had bothered to do it, you would see that this is all that there is...Ymir's stuff doesn't resolve with a "TLC" search, and it's nice that he copied all of that stuff right out of the same book I have, but if it was so fucking great and easy to use, then why isn't it happening... because it's TOO obtuse... you have to downsize it for less tech minds, that is unless your happy over in Methods explaining for the umpteenth time why the benzowacker didn't work and folks can't tell what intermediates they got because they did even know how to do simple TLC!
<----------- SEARCH ENGINE RESULTS TLC ------------------------------------->
Isosafrole
TLC plate was silica gel, mobile phase 97:3 toluene/ethyl acetate.
anethole
GC of the anise oil showed three peaks. one of these is about 90area% of all peaks. otto assumes that this is anethole. on TLC there was only one spot visible under UV-
light as well as with permanganate (RF 0.8 - 0.9 with Hexane/EtOAc 4:1).
(11) anethole is very active in UV. TLC is thus a good proof of proper separation.
RF: anethole 0.8 - 0.9, PMP2P 0.3 in Hexane/EtOAc 4:1.
That Pd(OAc)2 / tBuOH-H202 Wacker does not produce MDP2P with safrole. It produces a damned near perfect yield of the aldehyde which is useless for our purposes. This was proved by TLC. The sample was tested against safrole, isosafrole, 3,4MD propiophenone and MDP2P on whatman MK6F silicagel plates using 97:3 toluene/ethyl acetate mobile phase. The rf of the product produced by that oxidation was different than all of the mentioned compounds and also aminated w/ MeAM perfectly leaving me to conclude it was the aldehyde.
IR absorption information
,4,5-Trimethoxybenzaldehyde Synthesis
by Hest
5-Bromovanillin
Add 15,2g vanilin and 17,6g Br2 to 75ml AcOH, let the solution stir 1 h. Pour out the solution in 250mL ice-water. filter off the product. Dry and recrystallise from ethanol. mp. 162?C. TLC Rf 0,47 EtOAC:P 1:1
TLC Rf 0,35 EtOAc:P 1:1
<---------------------------------END
That is hardly sufficient for a MDMA visualization wouldn't you agree??
as to the psilocybin post on rhodiums site, it's very weak. I have the paper that gives 160 color points on every imaginable tryptamine using Erlich's, compared to a flower color scale... Nothing like that yet for PEA's though...
So before you go off like your flaming a newbee, take a look at exactly what I asked for. There is NOTHING in the hive that says anything about a visualization agent for MDMA for example all though most in the know realize that a Marquis test can do it for your ( dance safe etc. ) Is that anywhere here???
And is there anything that tells people how to roll their own plates easily??? NO! ( Nice wash info and spreading)
So I think someone should dump some karma points on you and you should CHILL out...maybe your just having a BAD DAY...
And then contribute something to this thread... you know, I really don't have to bother doing this if it is just a waste of time...
Infinite Radiant Light - THKRA
(Hive Bee)
05-03-02 19:22
No 304610
Thanks rhodium, that was exactly what I was considering writing up on the methods, now we just need the elutents and the visualization stuff...
btw a TLC search on your site, Thin-Layer Chromotography and Thin Layer Chromotography, only resolve to the psilo.txt file, not this info in zubrick...
Infinite Radiant Light - THKRA
(Chief Bee)
05-03-02 22:50
No 304654
That is because I scanned/uploaded this article today because you asked for TLC info, I haven't yet linked it from my main chemistry page.
(Moderator)
05-04-02 01:37
No 304707
No lugh, your full of shit... I have used the search engine, if you had bothered to do it, you would see that this is all that there is...Ymir's stuff doesn't resolve with a "TLC" search, and it's nice that he copied all of that stuff right out of the same book I have, but if it was so fucking great and easy to use, then why isn't it happening... because it's TOO obtuse... you have to downsize it for less tech minds, that is unless your happy over in Methods explaining for the umpteenth time why the benzowacker didn't work and folks can't tell what intermediates they got because they did even know how to do simple TLC!
I guess using the search terms "thin", "layer" & "chromatography" is too advanced for some newbees Would you care to share the title of that book that thread was copied from with us, or is that too much to ask?
As far as Post 304549 (lugh: "USTFSE!!!", Methods Discourse); Post 304428 (ClearLight: "TLC Time", Methods Discourse) suggests that there is no information on the Hive already, which isn't the case
And is there anything that tells people how to roll their own plates easily??? NO! ( Nice wash info and spreading)
So I think someone should dump some karma points on you and you should CHILL out...maybe your just having a BAD DAY...
And then contribute something to this thread... you know, I really don't have to bother doing this if it is just a waste of time...
It appears you weren't aware of that thread (despite what was said earlier), so a contribution has already been made (albeit not one that floats your boat). As far as the bad karma points, flaming such as this is one way to get them, be glad you haven't received such
What I'd like to request is that folks list their experience/research/cites for TLC workup. Please post commentary elsewhere and we'll keep this on track.
Post 108792 (dormouse: "Lab Suggestions -ymir", Novel Discourse) is the most thorough collection of TLC info currently on the Hive, thus fulfilling the requested criteria. As far as keeping the thread on track, there's no quicker way to go astray than to light up the flamethrowers 
Understanding the language of science is necessary for advancement in this field
(Daddy)
05-04-02 11:04
No 304827
(Rated as: excellent)
Post 211877 (wirewound: "Distillation: How to Set Up a Distillation", Methods Discourse),
""In one of the links ( http://orgchem.colorado.edu/hndbksupport
http://orgchem.colorado.edu/hndbksupport
http://www.indiana.edu/~orgchem/movies/c
This is an animated graphics movie on TLC procedure. LT/""
That one I just did from memory. Nobody seems to read, and I mean really READ, (and click the links), my sticky threads in Newbee and Methods..
Then I used the FSE, and guess what I found using my brain, the provided instructions at the bottom of the Search page, and thus filling in: "TLC" observe the use of the "..." !!! :
Search results
Matches 1 to 25 of 480
So, who's full of shit here? You've got a long way to go ClearLight!
Btw, I'm also curious what book you have with those Ymir articles in it, BECAUSE it doesn't come from a BOOK! It comes from a non published anymore, monthly magazine. LT/
PS: Why don't you copy and paste here that TLC info you have there at home (when you bought the sci-am Amateur Scientist CD Rom) f.ex. how to roll your own tlc plates out of microscope slides.
WISDOMwillWIN
(Hive Bee)
05-04-02 19:43
No 304919
Lugh gets a formal apology, he is NOT full of shit. Post 281214 (lugh: "Re: Thin Layer Chromatography", Chemistry Discourse) is an excellent site with all the methodology explained...
re: Labtop Book. The sci-am article was apparently taken from Zubrick and rhodium has done a great service and scanned it in on the link in the prior post.
I believe this answers all the methodology issues...
I did btw use the search engine and it did not pop up Lugh's prior post. It did pop the 423 TLC references that lab top came up with prior to this thread, and going through that was how I got the prior listing... maybe I misspelled it, maybe I didn't quote it or I did quote it... anyway, I did do the search, but my results were not as good as others...
Infinite Radiant Light - THKRA
(Pioneer Researcher)
05-05-02 00:46
No 304992
If can buy commercial UV TLC silica gel plates and micropippetes, that's definitive the solution. You can find short 254 nm UV lamps that can be armed in a fake money decetor, not really expensive, it's what we are actually using, and it gives you the light you need in research.
(Hive Bee)
05-06-02 20:53
No 305484
(Rated as: excellent)
Your Tax Dollars at work...
Here is a complete list of all various honey's, limits of detection, visualization reagant, reagent preparation, elutent/solute and color scale values for returned color...
http://www.ncjrs.org/pdffiles1/nij/18325
Enjoy!
( someone may wish to archive this in case it is made to disappear )
Infinite Radiant Light - THKRA
(Chief Bee)
05-06-02 21:06
No 305490
Great! I archived it right away to ../rhodium/pdf /colortestrefe
13 minutes from ClearLight posting it to me having it on my page!
(Daddy)
05-06-02 23:44
No 305540
I see very limited use for underground chemists for this, and they state that the chance of various false positives and negatives is quite big. It can in my humble opinion just give a VERY rough indication for very illiterate law enforcement officers to give them a reason to arrest an allready strange looking, acting or known abusive individual.
The real tests have to be done in a well equiped laboratorium, specialised on testing substances of abuse.
See for better tests:
Post 190939 (LaBTop: "Re: Ecstasy testing kits", Chemistry Discourse) Ecstasy testing kits (Damm nearly the same reagents as these guys use, ain't it? This was already published in 1977!)
Post 189956 (Chromic: "Ecstasy testing kits", Chemistry Discourse) Better read the whole thread with the above post and the PATENT in it, and then the last post is very usefull for street vendors and cooks alike:
lunatic_asylum (Stranger) 08-27-01 05:19
No 207690
Re: Ecstasy testing kits
Yes this should be the Simons Reagent!
There are three important reagents, which are very useful for testing pills.
1. Marquis-Reagent:
Into 50ml conz. H2SO4 there are dropped in, with ice cooling, 50 drops of formaline (35% in H2O!)
2. Simons-Reagent (this consists normally of three separate solutions):
1) 2% of Sodiumcarbonat in H2O
2) 4% sodium nitroprusside in MeOH
3) 10% Acetaldehyde in MeOH
(Maybe in this EZ-test there are two of them mixed together)
You have to drop one single drop of the reagents (in the mentioned order! 1., then 2.) onto your substance.
A blue colour indicates a N-substituted compound like MDMA, MDE, Meth or PMMA
4. Gallic Reagent
0,5% Gallic acid in conz. H2SO4
This reagent is very interesting, because is shows you methylendioxygroups!!!
In the literature it should turn into blue/green (in my experience it turned into yellow and after one minute into yellow/green to green).
It reacts in this way with MDA, MDMA, MDE, MMDA, BDB and MBDB. With other substances there is no reaction!!!
I have worked with this three reagents many times and I think, in combination, they are very useful (and cheap!!!).
Post 123336 (LaBTop: "Re: Seperating MDMA?", Newbee Forum) Seperating MDMA?
Post 123318 (EBOMB: "Seperating MDMA?", Newbee Forum) For a good laugh, and some good info, read this whole thread, that's better. LT/
WISDOMwillWIN
(Hive Bee)
05-07-02 01:04
No 305567
Oh well, my motiviation on this was to develop visualization agents for the TLC analysis, so you have "SOME" idea of what it was, and of course, what reagents to start with... nice that they give you the formulations... none of it will ever = a GC/MS or NMR, but then I don't have one handy...
I always had a fantasy about the ghetto variety quantitative spectrophotometer analysis, where you tlc'd the sample and the shot a digital image of the spot, that when compared to a reference in photoshop you could get some idea of how much you had... nice for plant sources at least..
They do have your favorite formulations listed...3
Looks like the same reagents as the old ex kits as well...although now dancesafe is marketing A10 mecke reagent that discriminates between dxm and x, gives a nice color for 2-ct-7 as well.
Thanks for the gallic acid, didn't know about that one..
Infinite Radiant Light - THKRA
(Moderator)
05-21-02 22:35
No 312076
(Rated as: excellent)
At alchemy_bee's request, from Analytical Chemistry 26 960-3 (1954)
Prepare a mixture of 28.5 g of silicic acid, 1.5 g of corn starch, 0.0011 g of Rhodamine 6G, and 54 g of water. Stir the mixture while it is heating on a water bath at 85°. After the mixture thickens, remove it from the water bath and add 20 ml of water. Spread the mixture to give a layer 0.02 in. thick on glass plates 5 in. x 7 in. Dry the plates for 20 minutes in an oven at 105° and, then, for 30 minutes at a pressure of 2 mm over potassium hydroxide.
Apply 1 to 2 mg of each sample or mixture dissolved in a low-boiling hydrocarbon in small spots along a line 2 cm from a short edge of the plate. Place the plate (with the samples near the bottom edge) in a covered battery jar. The bottom of the jar should be covered well with a solution of 10 to 15% ethyl acetate in hexane. Allow the solvent front to move 12 to 14 cm from the initial line. Remove the plate from the battery jar and allow it to dry in the air.
Observe the plate under ultraviolet light, and draw with a pencil a ring about each spot found. Spray the plate with a solution of 0.4 g of 2,4 dinitrophenylhydrazine in 100 ml of 2N hydrochloric acid to detect carbonyl derivatives, and again mark the spots. Use ultraviolet light to locate traces of ketones. Place the plate in an oven at 105° for 10 minutes to cause heat- and acid-sensitive components to appear. Compare the locations and appearances of the spots with those caused by known compounds. If a permanent record is desired, trace the edges of the spots on a piece of transparent paper.
(Hive Bee)
05-28-02 07:09
No 315073
(Rated as: good read)
Don't have access to full text, maybe someone will post the articles...
from: J Chromatogr Sci 1994 Jul;32(7):253-8
SFE with GC and MS determination of safrole and related allylbenzenes in sassafras teas.
Heikes DL.
Total Diet Research Center, Food and Drug Administration, Lenexa, Kansas 66285-5905.
Safrole (4-allyl-1,2-methylenedioxybenzene), a natural plant component of the aromatic oil of sassafras root bark, possesses carcinogenic and mutagenic activity. Legal restrictions have been placed on safrole as a food additive. However, sassafras teas continue to be accessible from health food establishments in the United States. Supercritical fluid extraction (SFE) with gas chromatographic-mass spectrometric (GC-MS) determination is utilized in the formulation of a rapid, accurate, and specific method for the determination of safrole and related allylbenzenes in unbrewed sassafras teas. Samples are extracted in a static-dynamic mode with CO2 at 690 bar and 80 degrees C with methanol as an extractor-added modifier. Levels of safrole exceeding 10,000 mg/kg (1.0%) are commonly encountered. Lesser amounts of other allylbenzenes, including eugenol and 4-allyl-1,2-dimethoxybenzene, are also reported. Recoveries of safrole and related compounds from previously extracted tea samples fortified at 100 and 1000 mg/kg ranged from 96 to 101%.
http://www.ncbi.nlm.nih.gov/entrez/query
and...
J AOAC Int 1997 Sep-Oct;80(5):1023-8
Liquid chromatographic determination of safrole in sassafras-derived herbal products
Carlson M, Thompson RD.
U.S. Food and Drug Administration, Minneapolis, MN 55401, USA.
A liquid chromatographic (LC) method was developed for determining safrole in herbal products derived from sassafras (Sassafras albidum), as well as related compounds such as isosafrole and dihydrosafrole. The procedure involves solvent extraction and isolation of analyte by reversed-phase LC with UV detection at 235 nm. Safrole is resolved from related compounds and other sample constituents including thymol, a component of thyme. A linear concentration range of 0.003-0.200 mg/mL was obtained for safrole, isosafrole, and dihydrosafrole. Limits of detection (LOD) and quantitation (LOQ) were e0.0015 and 0.0051 micrograms/mL for safrole, 0.0018 and 0.0061 micrograms/mL for isosafrole, and 0.0038 and 0.0125 micrograms/mL for dihydrosafrole, respectively. Intraday relative standard deviations (RSDs) for safrole (n = 5) from various samples ranged from 1.30 to 5.39% at analyte levels of 0.01-1.5%. Safrole contents of 26 samples including root bark powder, leaves, oils, tea concentrate, herbal extract tinctures, and herbal powder capsules ranged from < LOD for most leaf samples to 92.4% for an oil. Recoveries of safrole from fortified samples ranged from 83.6% for an oil to 117.2% for a tincture preparation. Safrole contents of 0.09-4.66 mg/cup were found for brewed teas prepared from sassafras root bark powders and tinctures.
http://www.ncbi.nlm.nih.gov/entrez/query
Infinite Radiant Light - THKRA
(Hive Bee)
07-14-02 04:25
No 332278
(Rated as: excellent)
Journal of Chromatography, 132(1977) 267-276
... A sensitive and specific chromogenic reagent for silica gel thin-layer chrmoatogrpahic detection and identification of indole derivatives
Summary: The chromogenic reagent described has been teseted with seventy-nine indole derivatives and found to be very sensitive and indole-specific. The lower limit of dectection on silica gel TLC was between 25 and 50 ng for most indoles.... The procedure was simple and required only 10 minutest from the time of spraying the TLC plate until full color development was reached. The colors had a wide spectral range from the yellow of the indole-3-glyoxylamide chromophore to the blue of the melatonin chromophore and were extremely stable.
page 268 "... The Erlich and van Urk reagenst are, to date the most specific chrmogenic reagents for indole derivatives, but color development is slow ( 3-8h) and the colos are not stable due to mineral acid retained on the silica gel layer. ... Color development with the salkowski reagent is rapid (15-30)min but the colors change quickly to non-diagnostic brown tones. ....
A spray reagent has now been developed that has a high sensitivity and specificity for indole compounds, gives rapid color development and color stability of the indole condensation products."
pg 269:
Solvents and Reagents:
(A) Van Urk Reagent: 1 g p-dimethlyaminobenzaldehyde...dissolved in 50 ml Conc. HCL (s.g. 1.190) and 50ml Absolute ethanol was added. This reagent is stable for several months at room temperature when stored in a brown glass bottle.
(B) Salkowski reagent (as modified by Tand and Bonner), 2.03g FeCl3*6H2O dissolved in 500 ml H2O and 300 ml H2SO4 (s.g. 1.840). This reagent is stable indefinitely.
Spray Reagent: The new TLC spray reagent used, was made up of Reagent A + Reagent B(1:3). The spray reagent may be kept at room temperature for several weeks.
TLC Solvent Systems:
1) Butanone-ethyl actectate-ethanol-water (3:5:1:1)
2) Propanol-Water(8:2)
3) Propanol-water-28%NH4OH (8:1:1)
4) Chloroform-MeOH-H2O ( 84:14:1)
Methods:
Visualization of indoles
After 1 or 2 dimensional TLC of indole standards or extracts... the plate was dried at 45°C until all traces of solvent had evaporated. ... Spraying was done in a fume hood... until the silica gel layer became transparent...
The plate was heated in a 100° oven for 5 minutes and allowed to cool to room temperature. The place wsa immersed in distilled H2O... agitated periodically for 1 min. (repeat 2x for non yellowing permanent gel record -CL)
The plate was removed from the last water wash and blotted with a dry paper towel. At this time the colors of the indole condensation products were evaluated (table 1: wet-plate color reading). The plates were then dried at 45°C (20-30min). the colors of the indole condensation products were evaluated once more (table 1; dry-plate reading). The colors of the indole condensation products are extremely stable and fade resistent. We have kept TLC plates at room temperature in the dark for more than two years wiht little of no faing of the original dry plate colors.
( partial list of colors )
Compound color region color name
Indole-3-acetic acid bluish violet Aconite Blue(180)
Tryptamine Blue Princess Blue(98)
5-HTP Violet Blue Sea Blue(119)
5-MEOTryptamine blue Princess Blue(98
(dry) Bluish Green langite Green(53)
( unfortunately 5meo-dmt, nn-dmt are not included in this table, -CL)
Infinite Radiant Light - THKRA
(Hive Bee)
07-15-02 08:53
No 332727
(Rated as: excellent)
So, after whipping up the above reagents, I tested it against 5HTP. I put a microscopic amount on a watch glass, added 4 drops of reagent, and then heated slightly on the flame...within 30 sec's it colorized! Sucess!
Anyway I got so inspired I pulled out my stash and did every indole I had... ( the dmt was left over from an extraction and failed to colorize...hmmm must still be in that emulsion
)I considered getting a color wheel and putting that up with the images, but how many of you have color wheels, so I grabbed the arm and hammer box for the red and yellow and the good ole' VM Naptha can for the blues... This should allow color correction for the purists, although the colors were different enough I wouldn't have any problem using them as they appear...
Anyway, for your viewing pleasure, here are the images...
This shows all of the tests in one shot...
This shows the psilocybin, as a reddish brown and the 5meo-DIPT as a greenish blue... These test are really sensitive...
Here is the lsd as a beautiful clear blue...this is 50 mics of pharmaceutical grade LSD-25 gc'd and mspec'd.
The DPT or DipropyTryptamine is a much deeper slate/blue green...
Here is the 5HTP, a cheap, legal way to test your solution, with another shot of the LSD-25
Here is a reference shot of the 5meo-DMT. It has a much more green tint to it, than the 5meo-DIPT, which has more blue... I may try another image if folks have any questions... and finally...
In this shot, you can see the 5meoDMT having more green in the color and the 5meoDIPT having a bit more blue green...
I hope this inspires folks to do more TLC, as you can see, it is a very useful and satisfying way to validate your results as you go through the experiments...
One thing I would like to point out, is that if you have isolated your DMT, 5meo-DMT, or LSD... you can make your self a standard solution of your compound. Use this visualization reagent with your standard and your compound to test ( extract from your last psychotria order, mh root bark etc.) and by shooting a digital image and comparing the density of the standard against the unknown, you can get ( if your careful ) a fairly good indication of the amount of "active ingredient" in your unknown materials...
Enjoy, and thx to all who make this possible!!!
Infinite Radiant Light - THKRA
(Stoni's sexual toy)
07-15-02 10:52
No 332762
Nice!
But it's still way too concentrated. On a TLC plate you have much smaller amounts present, so the colours will be lighter. Same when doing testing of biological material. When the concentration is too high it all seems to turn dark blue eventually. Have you tried diluting the coloured samples with water?
I'm not fat just horizontally disproportionate.
(Hive Bee)
07-15-02 18:07
No 332844
I'll dilute and check it, and also run a plate so the rf's can be seen... this was the initial testing for the chromophores...
extremely small amounts of material with this intensity...
Infinite Radiant Light - THKRA
(Distinctive Doe)
07-15-02 19:57
No 332884
The LSD looks right and I'm guessing its 1 hit of blotter.
So try to scale the others accordingly
Good work by the way!
foxy
Those who give up essential liberties for temporary safety deserve neither liberty nor safety
(Hive Bee)
07-15-02 20:37
No 332902
the acid is 50 micrograms... I can't scale the others as such since the tests are so sensitive... I probably put 1 milligram of the dpt and 5meodmt on each dish and they are really intense... the tests work down to 25-50 nanograms, so I'll try different dilutions and see what gives a clearer color indication... probably should make up some standards and give the formulation... any suggestions on standards folks?
Infinite Radiant Light - THKRA
(Hive Bee)
08-22-02 06:44
No 347588
(Rated as: excellent)
This web site details rolling your own tlc plates, by using the same materials you will use in your column. It gives % of binder and preparation methods.
Making TLC Plates from Bulk TLC Silica Gels
Many TLC users prefer to use pre-coated TLC plates, but others because of their special needs, or because they need special additives or a special thickness, coat their own TLC plates. This paper is a quick review of what is needed for the process.
Making TLC Plates from Bulk TLC Silica Gels
Many TLC users prefer to use pre-coated TLC plates, but others because of their special needs, or because they need special additives or a special thickness, coat their own TLC plates. This paper is a quick review of what is needed for the process.
http://www.emscience.com/chromsite/06100
Infinite Radiant Light - THKRA
(Hive Addict)
11-04-02 04:36
No 376220
In the Journal of Chemical Education, oct 96, #73, pg 979
Josef G. Krause writes:
"A recent suggestion to visualize spots on thin layer plates by applying phosphomolybdic acid reagent with a cotton ball (1) may not be suitable for all visualization reagents especially concentrated sulfuric acid. If spraying a reagent with a power pac type device is preferred for this or some other reason, we suggest spraying the reagent inside of a twist tie-sealed, clear-plastic kitchen garbage bag. In this way, spray reagents are completely contained obviating the need for spraying the plates in a fume hood, and cleanup is simple. "
So all you have to do is put your plates and your sprayer inside a clear trash bag, spray them, pull out your gear and toss the bag... this avoids the need for a fume hood and allow you to get a good mist on the plates.
Infinite Radiant Light - THKRA
(Hive Adickt)
11-05-02 01:08
No 376497
In my lab we just have the development regent (DNPH,PMo,Sulfuric ect.) in a glass(mason actual) , and then just dip the plate into the glass. No nasty sprayin and fine result's.
(Hive Bee)
11-11-02 03:18
No 378543
I thought that TLC might be more useful if applied in the synthesis process. One would get a known and spot against that ot verify one has the right stuff then as the procedur goes on one can check if the starting material is all used up and so on and always keep a sample of the material from each step so next time one can spot agains a known step material. By soing this one can check one's synthesis as one progresses through a reaction. Depending on the solvent used to wet the plates, I've always used a small Iodine crystals to develop my slide type TLC plates to visualize my progress, and if a step is not pure on can see various spots on the run of the slide. No spray nothing fancy just two jars where your slides can fit standing. I also suggest keeping notes and rf distance for future refrence because slides fade after a while . I prefer the NH3OH-chloroform -methanol solvent for my particular use in the synthesis of Methamphetamine I look for the chlorephedrine and starting material marks in my finish product spot.............this method is easy and although its not so colorful its effective and keeps me on track.
(Hive Addict)
11-11-02 09:39
No 378632
Hmm... when you roll your own on sg gf, sometimes it tends to fall off on the dip...+ the visualization reagent shouldn't dissolve the target material...
Infinite Radiant Light - THKRA
(Chief Bee)
06-01-03 19:45
No 437025
(Rated as: good read)
Here is the Journal of Chromatography article mentioned earlier in the thread (Thanks ClearLight!):
The Van Urk-Salkowski Reagent - A Sensitive And Specific Chromogenic Reagent For Silica Gel Thin-Layer Chromatographic Detection And Identification Of Indole Derivatives
Axel Ehmann
Journal of Chromatography 132, 267-276 (1977) (../rhodium/pdf /van.urk.indo
(Chief Bee)
08-16-03 21:51
No 453957
(Rated as: excellent)
Stains for Developing TLC Plates
Once a TLC has been developed, it is frequently necessary to aid in the visualization of the components of a reaction mixture. This is true primarily because most organic compounds are colorless. Frequently, the organic compounds of interest contain a chromophore which may be visualized by employing either a short or a long wave UV lamp. These lamps may be found as part of a standard organic chemistry research or teaching lab. Typical examples of functional groups which may be visualized through this method are: aromatic groups, a,b-unsat- urated carbonyl groups, and any organic compound containing other extensively p-conjugated systems. While exposing these TLC plates to UV light, you will notice that the silica gel will fluoresce while any organic molecule which absorbs UV light will appear as a dark blue spot. Circling these spots gently with a dull pencil will permit an initial method for visualization. Fortunately, there are a number of permanent or semi-permanent methods for visualization which will not only allow one to see these compounds but also provide a method for determining what functional groups are contained within the molecule. This method is referred to as staining the TLC plate, and experience will allow you to determine what functional groups will appear as what color upon visualization. Here are the most commonly employed stains, along with a typical preparation:
Iodine
The staining of a TLC plate with iodine vapor is among the oldest methods for the visualization of organic compounds. It is based upon the observation that iodine has a high affinity for both unsaturated and aromatic compounds.
Preparation
An chamber may be assembled as follows: To 100 mL wide mouth jar (with cap) is added a piece of filter paper and few crystals of iodine. Iodine has a high vapor pressure for a solid and the chamber will rapidly become saturated with iodine vapor. Insert your TLC plate and allow it to remain within the chamber until it develops a light brown color over the entire plate. Commonly, if your compound has an affinity for iodine, it will appear as a dark brown spot on a lighter brown background. Carefully remove the TLC plate at this point and gently circle the spots with a dull pencil. The iodine will not remain on the TLC plate for long periods of time so circling these spots is necessary if one wishes to refer to these TLC's at a later date.
Potassium Permanganate
This particular stain is excellent for functional groups which are sensitive to oxidation. Alkenes and alkynes will appear readily on a TLC plate following immersion into the stain and will appear as a bright yellow spot on a bright purple background. Alcohols, amines, sulfides, mercaptans and other oxidizable functional groups may also be visualized, however it will be necessary to gently heat the TLC plate following immersion into the stain. These spots will appear as either yellow or light brown on a light purple or pink background. Again it would be advantageous to circle such spots following visualization as eventually the TLC will take on a light brown color upon standing for prolonged periods of time.
Preparation
Dissolve 1 g of KMnO4 and 2 g Na2CO3 into 100 mL of distilled water. Ideally, these stains may be stored in 100 mL wide mouth jars. A typical lifetime for this stain is approximately 3 months.
Bromocresol Green Stain
This particular stain is excellent for functional groups whose pKa is approximately 5.0 and lower. Thus, this stain provides an excellent means of selectively visualizing carboxylic acids. These will appear as bright yellow spots on either a dark or light blue background and typically, it is not necessary to heat the TLC plate following immersion. This TLC visualization method has a fairly long lifetime (usually weeks) thus, it is not often necessary to circle such spots following activation by staining.
Preparation
To 100 ml of absolute ethanol is added 0.04 g of bromocresol green. Then a 0.1 M solution of aqueous NaOH is added dropwise until a blue color just appears in solution (the solution should be colorless prior to addition). Ideally, these stains may be stored in 100 mL wide mouth jars. The lifetime of such a solution typically depends upon solvent evaporation. Thus, it would be advantageous to tightly seal such jars in-between uses.
Cerium Molybdate Stain
This stain is a highly sensitive, multipurpose (multifunctional group stain). One word of caution, very minor constituents may appear as significant impurities by employing this stain. To ensure accurate results when employing this stain, it is necessary to heat the treated TLC plate vigorously. Thus, this may not be a stain to employ if your sample is somewhat volatile. The TLC plate itself will appear as either light blue or light green upon treatment, while the color of the spots may vary (although they usually appear as a dark blue spot). Typically, functional groups will not be distinguishable based upon the color of their spots; however, it would be worth while to make a list of potential colors of various functional groups as you experience variations in colors. This may permit future correlations which may prove beneficial when performing similar chemistry on related substrates.
Preparation
To 235 mL of distilled water was added 12 g of ammonium Molybdate, 0.5 g of ceric ammonium molybdate, and 15 mL of concentrated sulfuric acid. Storage is possible in a 250 mL wide mouth jar. This stain has a long shelf-life so long as solvent evaporation is limited. It may also prove worth while to surround the jar with aluminum foil as the stain may be somewhat photo-sensitive and exposure to direct light may shorten the shelf-life of this reagent. It is worth while to also mention that it would be beneficial to circle the observed spots with a dull pencil following heating as this stain will eventually fade on the TLC plate after a few days.
p-Anisaldehyde Stain
This stain is an excellent multipurpose visualization method for examining TLC plates. It is sensitive to most functional groups, especially those which are strongly and weakly nucleophilic. It tends to be insensitive to alkenes, alkynes, and aromatic compounds unless other functional groups are present in the molecules which are being analyzed. It tends to stain the TLC plate itself, upon mild heating, to a light pink color, while other functional groups tend to vary with respect to coloration. It is recommended that a record is kept of which functional group stains which color for future reference, although these types of comparisons may be misleading when attempting to ascertain which functional groups are present in a molecule (especially in complex molecules). The shelf-life of this stain tends to be quite long except when exposed to direct light or solvent is allowed to evaporate. It is recommended that the stain be stored in a 100 mL wide mouth jar wrapped with aluminum foil to ensure a long life time.
Preparation
To 135 mL of absolute ethanol was added 5 mL of concentrated sulfuric acid, 1.5 mL of glacial acetic acid and 3.7 mL of p-anisaldehyde. The solution is then stirred vigorously to ensure homogeneity. The resulting staining solution is ideally stored in a 100 mL wide mouth jar covered with aluminum foil.
Phosphomolybdic Acid (PMA) Stain
Phosphomolybdic acid stain is a good "universal" stain which is fairly sensitive to low concentrated solutions. It will stain most functional groups, however it does not distinguish between different functional groups based upon the coloration of the spots on the TLC plate. Most often, TLC's treated with this stain will appear as a light green color, while compounds of interest will appear as much darker green spots. It is necessary to heat TLC plates treated with this solution in order to activate the stain for visualization. The shelf life of these solutions are typically quite long, provided solvent evaporation is kept to a minimum.
Preparation
Dissolve 10 g of Phosphomolybdic acid in 100 mL of absolute ethanol.
Occasionally, you may find it necessary to develop or investigate other staining techniques; the following references may be helpful:
* Handbook of Thin-Layer Chromatography J. Sherman and B. Fried, Eds., Marcel Dekker, New York, NY, 1991.
* Thin-Layer Chromatography 2nd ed. E. Stahl, Springer-Verlag, New York, NY, 1969.
* Thin-Layer Chromatography Reagents and Detection Methods, Vol. 1a: Physical and Chemical Detection Methods: Fundamentals, Reagents I H. H. Jork, W. Funk, W. Fischer, and H. Wimmer, VHC, Weinheim, Germany, 1990.
* Thin-Layer Chromatography: Techniques of Chemistry, Vol. XIV, 2nd ed. J. G. Kirchner and E. S. Perry, Eds., John Wiley and Sons, 1978.
Source: http://www.ux1.eiu.edu/~cfthb/research/h
(Hive Bee)
08-17-03 05:05
No 454012
I'm surprised ninhydrin was not mentioned- it is a good stain for compounds containing amines or Boc-protecting groups, among others. Simply dissolve "a couple spatula-tip's worth" (what, maybe 10g? I always just eyeball it) in 95% ethanol. To visualize TLC plates, first circle UV-visible spots, then dip the plate in the ninhydrin solution. Lightly blot dry and heat with a heat-gun (hardcore hair dryer) until the plate takes on a brownish color/spots form.
Not sure about the lifetime of ninhydrin solutions- they always last long enough in lab to be used up, which may take a couple of months depending.
-SpicyBrown
(Chief Bee)
08-17-03 05:19
No 454015
It might be a cost issue, or because of the Carcinogenity of Ninhydrin.
(Moderator)
08-20-03 01:35
No 454586
(Rated as: excellent)
From Post 453943 (not existing)
Containment of Spray Reagents in TLC Spot Detection
Krause, Josef G.
J. Chem. Educ. 73, 979 (1996)
A recent suggestion to visualize spots on thin layer plates by applying phosphomolybdic acid reagent with a cotton ball may not be suitable for all visualization reagents especially concentrated sulfuric acid. If spraying a reagent with a power pac type device is preferred for this or some other reason, we suggest spraying the reagent inside of a twist tie-sealed, clear-plastic kitchen garbage bag. In this way, spray reagents are completely contained obviating the need for spraying the plates in a fume hood, and cleanup is simple.
Staining TLC Plate Using a Cotton Ball
Albert W. M. Lee and Zhong Zengpei
J. Chem. Educ. 73, 358 (1996)
Thin layer chromatography (TLC) is a simple but yet a very powerful analytical tool. It is widely used in unknown identification. Synthetic chemists routinely use TLC to monitor reactions and to check the collected fractions after column chromatography. After the TLC plate is developed, spot detection can be carried out under a ultraviolet lamp if the compounds are UV active, otherwise, some staining reagents have to be applied. Among many staining reagents, phosphomolybic acid (PMA) is widely used by organic chemists because most organic compounds can be visualized with PMA followed by heating. There are two common ways to apply the staining reagents, dipping and spraying. Dipping the TLC plate into the staining reagent may contaminate the reagent solution and may cause some diffusion of the spots. Spraying the TLC plate has to be carried in a fume hood and the mist generated can be very annoying.
We found that using a cotton ball to apply the staining reagent is a very convenient alternative. A cotton ball held by a pair of tweezers is dipped into the PMA ethanol solution. After the excess solution is squeezed out, the cotton ball is lightly wiped onto the TLC plate, followed by heating with a heat gun to visualize the spots.
Removing Silicone Greases from Round Bottom Flasks
Thomas J. Reilly
J. Chem. Educ. 73, 381 (1996)
If silicone greases are used on the standard taper joints of round bottom flasks they will eventually get inside the flask, contaminating the contents and introducing spurious peaks into the IR. and NM. spectra of samples. Removal of these deposits with solvents or conventional cleaning solutions is difficult, but the following method is fast and efficient: The flask to be cleaned is supported in a rubber ring and filled to the bottom of the joint surface with 5% aqueous hydrofluoric acid.
Caution: Hydrofluoric acid causes severe burns that may not become evident for several hours. This procedure should only be performed by an individual who is fully aware of the hazards involved and the safety precautions required. Hydrofluoric acid should never be handled by undergraduates.
After 20 minutes, the grease will separate from the glass surface in a thin film and can be removed from the hydroflouric acid by gravity filtration. The procedure can be repeated if necessary and will not cause visible etching unless the contact time exceeds 200 minutes. The hydrofluoric acid can be reused as long as it remains strongly acidic to pH paper.
Chemistry is our Covalent Bond
(Chief Bee)
08-23-03 00:39
No 455090
(Rated as: excellent)
Dip Reagents for Visualization in TLC
J. Chem. Educ. 73, A4-A6 (1996) (../rhodium /equipm
Thin-layer chromatography is used widely in the undergraduate organic laboratory (1-4). The technique often is illustrated with an early experiment involving the analysis of a mixture of colored substances such as those extracted from paprika or spinach. For colorless compounds, a step to make spots visible after development of the plate is needed.
Most Common Recommendations
* Commercially available plates can be used that incorporate a fluorescent dye in the adsorbent layer and make many substances visible when viewed with ultraviolet light.
* A TLC plate can be inserted into a jar containing iodine crystals to produce brown spots due to absorption of iodine from the vapor phase into the organic material.
Both methods, however, involve disadvantages. The UV method works only for UV active substances, and the iodine method is somewhat more general, but the spots produced tend to be fuzzy and indefinite, precluding fine resolution. We have found that these problems may be ameliorated largely by including "spray reagents" among the visualization methods available to students.
Reagents
* 2,4-Dinitrophenylhydrazine (used to detect aldehydes and ketones)
* Potassium permanganate (detection of alcohols, alkenes, and other oxidizable compounds)
* Phosphomolybdic acid (non-specialized reagent)
The spots resulting from the use of these solutions usually are well-defined and often appear in characteristic colors. These solutions are applied to the TLC plate with any of several types of spraying devices available from major chemical companies. This step, however, has several objectionable features that have discouraged the use of these reagents in most student laboratories.
Objectionable Features
* The process is wasteful. Only a small fraction of the solution ever reaches the plate.
* Unless scrupulously maintained, sprayers tend to clog and splatter, resulting in an uneven coating.
* Most serious is the fact that most of the reagent is released into the atmosphere to remain as a noxious contaminant.
Employing a Dipping Technique Avoids Disadvantages
We have avoided these disadvantages by employing a dipping technique with the reagents. The solutions are stored in plastic centrifuge tubes of proper size (a few centimeters longer and a few millimeters wider than the TLC plate). After development, the plate is held at the solvent front end with forceps, submerged in reagent up to the solvent front, and immediately removed. Contact time with the solution should be kept to a minimum. Spots usually begin to emerge almost immediately but become more definite over a period of up to one hour. In some cases (e.g., after the phosphomolybdic acid dip) spot development requires the application of mild heat such as hot air from a hair dryer. A large number of general and specialized visualization reagents are listed in an easily available chemical-biochemical catalog (5). Use of such reagents with the dip technique should lead to optimal results with a minimum of cost, mess, wastage, and environmental contamination.
Materials and Procedures
The TLC plates are 2.5x7.5-cm plastic sheets with a silica gel coating containing a fluorescent dye (J. T. Baker catalog number IB2-F). The dip solution containers are 50 mL polypropylene centrifuge tubes, 2.8 x 11.5 cm, with screw cap (Fisher Scientific Company catalog number 05-538-55). The phosphomolybdic acid reagent is purchased most economically as a 20% solution in ethanol (Aldrich Chemical Company, catalog number 31,927-9). The permanganate dip was prepared as an aqueous solution, 1% in KMnO4, and 2% in K2CO3. Brady's reagent (6) was employed for the 2,4-dinitrophenyhydrazine solution.
Literature Cited
1. Fessenden, R. A.; A, Fessenden, J. S., Organic Laboratory Techniques, Brooks/Cole: Pacific Grove, CA, 1993, p 188.
2. Mayo, D.W,; Pike, R. M.; Trumper, P. K. Microscale Organic Laboratory; 3rd Ed. John Wiley New York, 1994, p 103.
3. Wilcox, C. F. Jr,; Wilcox, M. F., Experimental Organic Chemistry, Prentice-Hall: Englewood Cliffs, NY, 1995, p 131.
4. Zanger, M.; McKee, J. R. Small Scale Syntheses: A Laboratory Textbook of Organic Chemistry; William C. Brown: Boston, 1995, p 52.
5. Sigma Chemical Company Catalog, 1995; p 941.
6. Shriner, R. L.; Fuson, R. C., Curtin, D. Y., Morrill, T. C., The Systematic Identification of Organic Compounds, 6th. Ed.; John Wiley; New York, 1980, p 162.
(Chief Bee)
08-23-03 15:10
No 455196
(Rated as: good read)
Thin-Layer Chromatography - Variations on a Theme
J. Anwar, S. A. Nagra, M. Nagi
J. Chem. Educ. 73(10), 977 (1996) (../rhodium/djvu /tlc-j.chem.
(Chief Bee)
11-27-03 09:57
No 473443
(Rated as: excellent)
TLC Developing Chamber for Screening Column Chromatography Fractions
Samuel G. Levine
J. Chem. Ed. 73(1), 77 (1996)
Column chromatography, in all of its varied forms, is the mainstay technique for preparative separations in the organic chemical laboratory. The subject was possibly first introduced to undergraduates by Fieser's 1955 laboratory manual that includes complete instructions for preparing and running a column as well as two experiments that result in the separation of colorless substances. By contrast, most of the current texts include only less ambitious column chromatography experiments involving the much easier task of separating colored substances such as dye mixtures, plant pigments, or ferrocene derivatives. Barring the use of very expensive automatic monitoring equipment, the successful separation of colorless substances requires some means of screening the eluate fractions so that those of like composition may be combined. This process is customarily accomplished by thin layer chromatography (TLC). We describe here a novel TLC development chamber that greatly enhances the efficiency of this task.
The chamber (see figure), designed for use with 25x75 mm plastic TLC plates, is constructed from a 100-mm length of 25-mm OD Pyrex tubing of standard wall thickness. After both ends are sealed, a narrow 80-mm long slit is cut* along the length of the tube, equidistant from the ends. The chamber may be mounted conveniently, slit facing up, on a short length of 2x4 lumber with the help of two small lumps of "Hold-It" or other putty-like material. Ten fractions may be spotted 7 mm apart along one edge of the plate. The plate is then lowered through the slit into the development chamber that has been charged previously with 2 mL of eluant. (Care must be taken to maintain a horizontal orientation of the plate while lowering it into position.) Note that the upper edge of the plate extends a short distance outside the chamber. After elution is complete (45 sec using EtOAc/hexanes 1:4 as eluant) the plate is removed, dried, and subjected to spot visualization by any appropriate means. Viewing the plate will then disclose a pattern of fraction composition as a function of fraction number. If greater resolution of low Rf spots is desired, this often can be achieved by extending the elution time, e.g., to two minutes.
The methodology described here is advantageous for several reasons.
• It is very rapid.
• Highly efficient use is made of the least expensive form of commercial TLC plates.
• The perfectly straight base of the chamber results in very even flow of solvent.
• Very little solvent is required.
TLC developing chamber.
* Cutting was performed with a 3/32-in. mounted diamond-point cylinder from Starlite Industries, P. O. Box 990 Rosemont, PA 19010-0911; Cat. #117045, $15.60.
(Chief Bee)
11-29-03 01:40
No 473703
(Rated as: good read)
I did not find any info regarding the determination of a solvent system for a given substance. How is this determined??
Trial and error. You test different solvent mixtures until you find one which makes most of your spots end up between Rf 0.2 and 0.8 (very approximate - just see this as your highest goal, often spots either have a strong tendency to run away (non-polar) or stay beind (polar) on the TLC slide.
First try with a medium polarity solvent mixture (like petroleum ether/ethyl acetate in a 1:1 ratio). To make the spots run higher, use a more polar solvent mixture (like petroleum ether/ethyl acetate in a 1:5, or even 1:10 ratio). To make the spots run lower, use a less polar solvent mixture (like petroleum ether/ethyl acetate in a 5:1, or even 10:1 ratio). If 100% ethyl acetate isn't polar enough, you can begin mixing in some methanol or isopropanol (10% or so).
If you run TLC on amines, and if they tend to streak (form long oval spots) it usually helps to add 1% triethylamine to the solvent system. To find suitable solvents to use, see the polarity index here (and you'll see if they are miscible too, which naturally is a prerequisite): ../rhodium/pdf /solvent.misci
Try to only mix solvents which have roughly the same evaporation rate or you will get inconsistent results, as one component will evaporate faster, changing the composition of the mixture over time.
(Moderator)
11-30-03 18:30
No 473922
(Rated as: good idea!)
Way better than triethylamine in the eluent is a vial with conc. aqueous ammonia in the chamber. This will not cause artifacts caused by the 'TEA-front' which might result in spot-doubling or smearing.
(Chief Bee)
11-30-03 21:56
No 473935
The latter.
(Chief Bee)
03-15-04 17:17
No 495296
(Rated as: excellent)
Cactus Alkaloids XXVII.
Use of Fluorescamine as a Thin-Layer Chromatographic Visualization Reagent for Alkaloids
R.L. Ranieri & J.L. McLaughlin
Journal of Chromatography 111, 234-237 (1975) (../rhodium/pdf /tlc.fluoresc
The Hive - Clandestine Chemists Without Borders
(Chief Bee)
05-01-04 22:17
No 504225
(Rated as: excellent)
Identification of Pharmaceuticals via Computer-Aided Thin Layer Chromatography
Macherone, Anthony J., Jr.; Siek, Theodore J.
J. Chem. Educ. 77, 366-367 (2000) (../rhodium /equipm
Supplementary Info(PDF) (../rhodium/equipme
Supplementary Data (ZIP) (../rhodium/equipme
Abstract
In toxicology laboratories, thin-layer chromatography (TLC) provides a quick and accurate method for qualitative identification of unknown biotoxins that may be present in a fluid or tissue sample. These varied samples are presented to the toxicologist for analysis on a routine basis and also during emergency situations or after a death. The ability of TLC to identify or rule out hundreds of compounds in a single analytical run makes it amenable to emergency toxicology and forensic chemistry. However, the ability to decipher the various reactions and elicit meaningful results from the raw data can take years of experience. It would be useful therefore, for analysts to obtain a firm background in TLC while still in academic training. This analytical laboratory experiment demonstrates the methodology of TLC in its relation to toxicology and forensic chemistry. It is easily adapted for high school seniors or undergraduates and employs experimental techniques associated with TLC and post-lab data analysis with concomitant introduction of concepts. The procedures are designed to introduce the student to the concepts, mechanisms, methodology, and reactions of TLC while building skills in record keeping, data analysis, and deductive reasoning.
____ ___ __ _
Rapid, Simple Quantitation in Thin-Layer Chromatography Using a Flatbed Scanner
Johnson, Mitchell E.
J. Chem. Educ. 77, 368-372 (2000) (../rhodium /equipm
Supplementary Info(PDF) (../rhodium/equipme
Supplementary Data (ZIP) (../rhodium/equipme
IGORPro 5 Software (http://www.wavemetrics.com/Products/IGO
Abstract
A standard flatbed scanner is shown to be a viable tool for quantitative thin-layer chromatography (TLC) plate analysis. Simply scanning a visibly stained TLC plate into a computer substitutes for much more expensive plate readers. With common image analysis software, "elution" profiles can be obtained. The resulting "chromatograms" can be analyzed in the same manner as other chromatograms. Iodine-stained cholesterol and cholesteryl esters are shown to yield nonlinear calibration curves, but the overall sensitivity is excellent for such a simple method. Detection limits are submicrogram for heavily stained spots. Spot intensity, and therefore detection limit, depends strongly on the amount of time the spot is exposed to iodine. Reproducibility is excellent for spots deposited by aspiration from a glass micropipet. Peak area and peak height relative standard deviations (RSDs) were generally below 5%, and retention factor precision was as low as 0.8% RSD.
The Hive - Clandestine Chemists Without Borders
(Chief Bee)
05-31-04 17:22
No 510539
(Rated as: excellent)
What solvent mixture has the most eluting power? Petroleum ether/ethyl acetate (1:3) or is it chloroform/ethyl acetate (1:1)?
Use the table below to find out.
The Hive - Clandestine Chemists Without Borders
(Chief Bee)
09-30-04 19:34
No 533925
(Rated as: good read)
The Rf Value As A Constant In Thin-Layer Chromatography
J.H. Dhont
Journal of Chromatography. 202, 15-20 (1980) (../rhodium/pdf /tlc.values.a
Summary
A comparison has been made of the results of a number of experiments concerning Rf values in thin-layer chromatography randomly chosen from the literature. The study led to the conclusion that in thin-layer chromatography a constant Rf value can be obtained.
The Hive - Clandestine Chemists Without Borders