A rapid analysis to check the organic or inorganic nature of a compound is to observe what happens on heating. Organic compounds will carbonize with characteristic smell or decompose with developing of gases. inorganic compounds may change their nature (e.g. from salt to oxides) but you have no carbonization. The problem remains if you have an organometallic compound.

thanks a lot for your answer I am going to check it , I appreciate your effort.

Just take some crystals on the end of a spatula and then introduce it in a flame, if it is melts or burns without white vapors then it is an inorganic compound and if you see white vapors or smoky vapors, it is organic. This is a very basic test which is used for this purpose.

Another test is to apply the compound on a TLC plate (no need to develop the plate). You can use any fresh plate for this purpose. Once applied a spot on the plate, spray the plate with conc. sulfuric acid. Organic compound will be charred and turn black in color.

Alternatively, you can also keep the plate in iodine chamber. Iodine vapors will give a dense spot with organic compounds.

thank @Dr.Alok Nahata, sounds great new suggestions , I will check them as well

Use different fuctional gp tests

Put in slightly hot concentrated sulfuric acid; if turn black you are moderately sure that it is an organic compound

Check Melting Point. organic compounds generally have lower melting point than inorganic compouds.

Alok's answer is going to solve most probably your problem.

May I add some proposal to do the rest if you are no convinced yet? Try to observe the crystals in a microscope or simply in the eyepiece of a microscope in the opposite direction. If any there is any right angle between two faces, it would tell you that its space group is a cubic one, thus speaking for a mineral stuff. Indeed, there is no way for an organic molecule (or for any association of them: two, four), to fit into an asymmetric "unit cell" and to form a cubic body or face-centered cubic system crystal !

Doing so, you would also be in the possibility of admiring the beauty of nature more closely!

Take your chance

Jo

By doing crystallography of the compound you can easily find what is. Another way is to burn the compound.

I guess you don't have much material but you could do some physico/spectrum analysis and characterization of the crystals and/or crystallography in a beam.

I think most suggestions were about considering them as natural organic compounds with high "calorie" yield when burning.

Some sugg. above are simple anyway so hope they work. If acetonitrile works to dissolve you could have analyzed the MW by HPLC too.

Check some links too such as:

https://www.youtube.com/watch?v=XQ24s3t9qxc

http://wwwchem.uwimona.edu.jm/lab_manuals/c10expt25.html

Put little crystals on porcelain spoon/cup and burn with fire, if turned into black charcoal, then your crystals are organic compound(s).

Thanks all. It's always been my pleasure to share the information with all of you. I really acknowledge the positive response received from all of you which encourages me to do my best.

Best Regards

thanks all I appreciate your valued answers.

I have tested the heating test for the crystals, I think it is inorganic compound! but some thing I have not experienced before happened! that when I have heated the crystal sample on the spatula it popped up from the spatula with a sound resemble to the sound of capillary tube break "very little tik" and when I heated it in a tube it made the same thing but this time it crumbled ! can any body share his knowledge regarding to this notes!

thank again and thanks in advance

Most probably, the crystals loose the water (or whatever the solvent is) molecules that are "co-crystallized" and that cannot resist at such high temperature. Thus a sudden decomposition appears that makes these noises !

@Joseph Vercauteren thanks a lot

@Joseph Vercauteren... Exactly .. I agree with you.

@Dr. Alok Nahata thank you, I appreciate your effort to help

Excellent answer by Dr. Alok Nahata-- very simple and practical solution

I have simple question to Helmi Yousif Alfarra, Sir will you please describe the primary objective of your experiment , the origin/ background of this research project? and the end user of your research work? Pls be kind to reply

Carry out and infrared (ir) spectrum and check the spectrum obtained. This will tell you if it is organic or inorganic. You need a few milligrams of the crystaaline substance you have to carry out an ir analysis.

If you take melting point, Organic crystals have low melting point about 300, where as inorganic crystals melt at much higher temperature.

Burn them

very nice question I faced the same problem while I was doing Ph.D

and I tested flame test, Iodine vapours test

Thus I dicided that is inorganic compound

ingenerally these types crystals will come with more polar solvent like alcohol extraction

and when you run the column with more polar solvents

Good answer from Dr. Alok Nahata. However, I think IR spectrum of the crystal can also be of immense help.

Break them with a neddle, if they break hadrly they are inorganic, if they disolve, they are organic; you can also ask for special color marker (blue) that colors only organic crystals in blue...

Take the melting point if the value is < 300 you have a organic compound

I think Dr. Alok Nahatank has got the right simple answer

The low melting point is not enough. The solid organic substances are dissolved in water if it is due to their polarity and by the formation of hydrogen bonds with water, but also are poor conductors of electric current, in sequence one would help further measure the conductivity of the solution obtained, then the inorganic salts are good conductors in the molten state or in aqueous solution

IR spectrum can distinguish them well. But still learn something from Dr. Alok Nahata .

in anyways if you want to find out I think it might be inorganic as it is from ethanolic extract .you take AAS or if have more take xrf to find out which inorganic salt . I wasted time on one such comppound sening NMR again and agian .Most probably compound is inorganic

if it is soluble in water ,it should be inorganic, salts like NaCl, Na2SO4 ---- etc. are obtained from column ,U can take NMR in warer, it will be clear.

I agree with simple test recommended by Dr.Alok Nahata.

While doing my PhD I faced the same problem as Helmi, I synthesized few new compounds, got very good crystals, but they were its salt form, it was confirmed by determing their crystal structures. Dr Alok Nahata has recommended very good tests, but you should also go for IR, NMR and crystal structure.

YA, I am also agree with Dr. Alok ,

Just you can check your process; It may be salt presents in your crude product.

Or you can try more high polar solvent in your silica column and after that you hold your product more then one or two day, then you got some crystals

yes i am also agree with Dr.Alok Nahata and get nmr in h2o and xrd may help you ...

Elemental analysis would give you the empirical formula of the compound.

dear helmi yousif

presently i myself has encountered this problem while carrying out chromatograohy on crude methanolic extract of a plant... these were water soluble anh sparingly soluble in methanol... i dissolved these crystals in water and applied it on TLC... mobile phase used was chloroform-70:methanol-30:water-4... Rf value was round about0.20....after developing TLC with conc, sulfuric acid it produced dark grey spot.... it was suggested to be sugar.... further carbohydrate test confirmed it being sucrose...

i think it will be of some help...

Burn test will distinguish organic from inorganic compound.

Yes, Alok Nahata idea is good. It is the test for distinguishing Organic compounds from Inorganic compounds.

Sure. As Alok Nahata said, just burn it using a spatula. Few mg is enough for this. Black fume is Organic otherwise inorganic

Burn test will be very useful.Spot the sample in TLC plate and spray with con. sulphuric acid. Charring indicates presence of organic compound.

Many factors do play a role in column chromatography. It is usual experience that if the fraction eluded with methanol/alcohols with more than 10% amount of water, the in-organic compounds inherent with the silica gel get into the fraction. Over a period of time, say three to four days, lot of crystals appear giving the false impression that the compound of some interest is getting crystallized. Of all the tests mentioned, I think the burn test and thespot test on a TLC plate sprayed with sulphuric acid is very helpful. Iodine chamber is useful if the compound/crystal has at least one double bond. Otherwise no iodine would be absorbed. Sugars /glycosides usually do not easily yield crystals. One simple wild rule is if you have loaded a fraction of the herb extracted with hexane, benzene, chloroform, ethyl acetate, methanol, and if the crystals occured in fractions involving more organic solvents, then the crystal can be an organic one. If a 70 % or 50% alcoholic extract loaded on a column and the fractions eluting with mixtures of alcohol and water, then the crystals may be of in-organic in nature. Such in-organic crystals may in all probability be of the column material rather than from the plant in question.

your compound is almost not dissolved i nwide range of solvents with different polarity. So moslty, this could be an organic compound. you couldnt run TLC also, because your compound don't elute. So better do melting point analysis and possbile elemental anlysis

Dear Dr H. Alfarra,

You rose this point half a year ago, from now. Recurrently, some proposition is made to add an explanation to the phenomenon you saw, including both types of crystals (organic and inorganic). However, so far, it turns out that you revealed that most probably the crystals are "inorganic", but this is not sure yet. In order to close the discussion and to enrich every reader of this full explanation, could you confirm what type they are ? Did you finally discover what was the trick ?

Many thanks in advance.

Sincerely,

Joseph

Elemental analysis is best way to determine though it is destructive method and if you don't want to loose your crystal then do single crystal analysis

Do flame test with copper wire or platinum wire.

Mr.Alfarra,

usaully such kind of crystal appear in the plant extracts, due to the presence of inorganic impurities in organic solvents.The bio active compounds will be in needle shape crystal or powdery mass that too lightly coloured like brownish, yellowish or greenish.. if the crystal is in cube shape and is soluble in water, then it might be an inorganic compound. better take an IR spectrum, simple we can identify .

i also got three kinds from three plants in huge amount which proves it is not impurity but i am still studyng if its a complex of potassium and organic part.I am sure its potassium compound .I f you have got result please share with me. And if anyone has answer to these crystals please advice.