I have a picrate that is made alkaline by ammonia followed by extraction with dichloromethane until the base was exhausted. The required eluent for the silica gel column chromatography is acetone: water: ammonia (90:7:10). What other chemicals should I use for an alternative eluent? to further purify my sample?
It depends on the type of alkaloids. Some of them needs normal solvents and others need to change the PH
An alternative eluents for purifying alkaloids in column chromatography you can use chloroform or ethyl acetate.
Also check http://www.jocpr.com/articles/the-extraction-separation-and-purification-of-alkaloids-in-the-natural-medicine.pdf
The powder material is moistened with water and mixed with lime, which combined with acids, tannins and other phenolic substances and set free alkaloids (if they exist in the plant as salts). Extraction is then carried out with organic solvent such as ether or petroleum spirit. The concentrated organic liquid is then shaken with aqueous acid and allowed and to separate. Alkaloidal salt are now in the aqueous liquid, while many impurities remain behind in the organic liquid. https://www.yourarticlelibrary.com/biology/plants/the-process-of-extraction-of-alkaloids-from-plants/49418
Process-B: The powder material is extracted with water or aqueous alcohol containing dilute acid. Pigment and unsaturated materials are removed by shaking with chloroform or other organic solvents.
The free alkaloids are then precipitated by the addition of excess sodium bicarbonate or ammonia and separated by filtration or by extraction with organic solvent.
Large-scale extractions based on the above principles are sometime done in the field and the crude mixtures of alkaloids afterward sent to a factory for separation and purification.
This has been done for cinchona and coca alkaloid in South America and Indonesia, the crude alkaloid then being sent Europe, USA or Japan for purification.
The separation and final purification of a mixture of alkaloids may sometimes be done by fractional precipitation or by fractional crystallization of salt such as oxalate, tartrate or pirate. Chromatographic methods are particularly suitable if the mixture is a complex one and if small quantities of alkaloids will office.
https://www.yourarticlelibrary.com/biology/plants/the-process-of-extraction-of-alkaloids-from-plants/49418
Volatile liquid alkaloids such as nicotine and coniine are most conveniently isolated by distillation. An aqueous extract is made alkaline with caustic soda or sodium carbonate and alkaloid distilled off in steam. Nicotine is important insecticide, and large quantity of it are prepared those part of the tobacco plant which cannot be used for tobacco manufacture. https://www.yourarticlelibrary.com/biology/plants/the-process-of-extraction-of-alkaloids-from-plants/49418
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