A method for synthesis of a specific organic compound is investigated. Chromatographic separation and fraction collection procedures were performed for the resulting mixture (liquid) of the proposed reaction to obtain supposed pure compounds. Is it enough to rely on recrystallisation procedures to prove purity of compounds? Is instrumental analysis required (NMR, IR) to prove purity, and if so, how?
Check for its physical constants like N.P., M.P. and see how far they are in harmony with the reported values for pure ones. Any deviation in the values reflect upon purity level. Instrumental analysis like LC-MS, RTF, NMR etc.will help in identifying the unknown ones and it's qualitative and quantitative analysis precisely.
Yes. There are two ways - determine all impurities or determine the concentration of the main compound in this "pure compound". The determined conc. divided by the expected conc. (mass of comp. per volume of solvent) gives the purity. One thing- you need a high purity standard of that compound for calibration.
Regards
G
.Simple is good. Thin-Layer chromatography is vary adapatable in providing a clean sample: put spots on a standard plate (glass or even plastic slides of silica gel), develop in different solvent mixtures: (non-polar to polar) and visualize by charring. (sulfuric acid spray and heat). You should soon find your "spot of interest", extract it to get pure material (called "Preparative TLC").
You should check purity of the obtained residu via 13C and 1H NMR after coulmn chromatography using suitable solvent mixture. Coulmn chromatography is usually the best separation and purification technique in organic chemistry. If your residu is not pure, you may search a new suitable solvent mixture using Thin Layer Chromatography (TLC).
Hey Sam,
in organic compounds the water and salt content are often not included in the impuritys. This depends on the analytical method which was used. If there is no reference compound with known purity I think quantitative NMR is the best way.
There are many ways to get a "reference compound with known purity". We used to make our own, using our own chromatography systems. (Thin layer/ column/ liquid). That is where a "reference compound" comes from.
What is the target product? Preparative TLC is recomended or purification with sephadex
After recrystallization or distillation, Checking melting or boiling point pending on the nature of the compound. Instrumentally checking the absorbance, the function groups.
A samples way to check the purity of a compound is thin-layer chromatography (TLC)
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