Rf values needed....

Alice · Fri Feb 11, 2005 9:53 pm

hehe
finaly lovely tryptamines forum is open :)

anyway l need little help finding Rf's of some chemicals

actualy i wonder about rf's for 3 different solvent systems

one would be hexane/chloroform 3:1
one would be methanol/dichloromethane 1:10
and the third would be methanol alone

matrix: silica gel or basic/neutral/acidic alumina

chemicals.....
1: ergocriptine
2: ergine
3: lsd
4: iso-lsd

10x in advnce Smile

bzzzzzzzzzzzzz

java · Consumer

Although not an answer to your request .........there is some added info using the search function ......tlc, I found this, could have some rf values,

..........indole tlc

moecat · Wed Feb 16, 2005 8:36 am

IndoleAmine · Dreamreader Deluxe

I don't know if this helps you - guess not...

(you know the trick with the small UV light to make the different elutions/fractions visible?)

wyndowlicker · Member of the Month

Hey now,

What is it exactly your looking for?Im not familiar with the abreviation RF.Could you please explain.

Question

The bus came by and I got on,thats when it all began.

moecat · Fri Feb 18, 2005 11:19 am

Alice · Fri Feb 18, 2005 7:46 pm

10x beez
some posts heplped alot....

still looking for rf for ergocriptine

btw is there any soft that can emulate chromotography?
like u set the solvents and matrix and needed chemical and it gives ya Rf?
would be realy nice one Smile

java · Consumer

Z. Anal. Chem. 294 (1979) 47
Szepesi G.

........source

Substances:
ergometrine, ergometrinine, ergotamine, ergocornine, ergocriptine, ergocristine, ergotaminine, ergocorninine, ergocriptinine, ergocristinine, dihydroergocornine, dihydroergocriptine, dihydroergocriptine, dihydroergocristine

Keywords:
alkaloids, ergotoxins

Chromatogram:
Legend: Alkoloid/Rf

Ergometrine
0.78
Ergometrinine
0.73
Ergotamine
0.65
Ergocornine
0.60
a-Ergocriptine
0.53
b-Ergocriptine
0.50
Ergocristine
0.45
Ergotaminine
0.38
Ergocorninine
0.33
Ergocriptinine
0.25
Ergocristinine
0.16
Dihydroergocornine
0.63
a-Dihydroergocriptine
0.58
b-Dihydroergocriptine
0.55
Dihydroergocristine
0.51

Concerning questions to literature applications please contact the cited author/s.

.

Alice · Sun Feb 20, 2005 1:36 am

wow man u own!!!!! Smile

10x alot

wyndowlicker · Member of the Month

Hey now,

I didnt realize you were refering to TLC rf values. My fault:lol:

-----------------------------------

The bus came by and I got on thats when it all began

wyndowlicker · Member of the Month

TLC - Retention Factor (Rf)
The retention factor, or Rf, is defined as the distance traveled by the compound divided by the distance traveled by the solvent.

For example, if a compound travels 2.1 cm and the solvent front travels 2.8 cm, the Rf is 0.75:

The Rf for a compound is a constant from one experiment to the next only if the chromatography conditions below are also constant:

solvent system
adsorbent
thickness of the adsorbent
amount of material spotted
temperature
Since these factors are difficult to keep constant from experiment to experiment, relative Rf values are generally considered. “Relative Rf” means that the values are reported relative to a standard, or it means that you compare the Rf values of compounds run on the same plate at the same time.

The larger an Rf of a compound, the larger the distance it travels on the TLC plate. When comparing two different compounds run under identical chromatography conditions, the compound with the larger Rf is less polar because it interacts less strongly with the polar adsorbent on the TLC plate. Conversely, if you know the structures of the compounds in a mixture, you can predict that a compound of low polarity will have a larger Rf value than a polar compound run on the same plate.

The Rf can provide corroborative evidence as to the identity of a compound. If the identity of a compound is suspected but not yet proven, an authentic sample of the compound, or standard, is spotted and run on a TLC plate side by side (or on top of each other) with the compound in question. If two substances have the same Rf value, they are likely (but not necessarily) the same compound. If they have different Rf values, they are definitely different compounds. Note that this identity check must be performed on a single plate, because it is difficult to duplicate all the factors which influence Rf exactly from experiment to experiment.

to view document photos:
http://orgchem.colorado.edu/hndbksupport/TLC/TLCrf.html

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The bus came by,and I got on thats when it all began.

methyl_ethyl · Riedel De Haen

As WyndowPane Wink

bee stated,

The Rf for a compound is a constant from one experiment to the next only if the chromatography conditions below are also constant:

solvent system
adsorbent
thickness of the adsorbent
amount of material spotted
temperature

So in other words, the RF's you read anywhere in literature will be irrelevent to you unless you are using the exact same solvent system, plate, load, temp etc. The best way to compensate for this within your own assay is to purchase analytical standards that you can run with your unknowns and from there you can determine the RF's of your unknown with that of a known standard.

For the rest of the world you will just have to replicate exactly the assay that was performed in the literature in order to use the relative RF's that correspond laterally to your own assay conditions. And even that is stretching it a bit.

Take this from someone that has never even seen a TLC plate before, or don't... 8)

much_love

methyl_ethyl