kilomentor

Treatment of a solution of a chemical product is a trivial matter if you are working in an Erlenmeyer in the laboratory, but much more problematic for a chemical process engineer at-scale in the plant. Charcoaling as a means of removing small (<2%) amounts of contaminating substances from an organic preparation has long been known. Use of a plug of a solid adsorbant (such as silica or alumina) through which a solution of the slightly impure substance is passed for the purpose of purification is also long known.

There are other similar techniques. The use of these methods has been empirical and a matter of one at a time testing trial and error. In particular the selection of a solvent to be used in combination with these solid adsorbants was empirical and this was a very real problem because it is often the combination of the correct choice of solvent and the correct choice of solid adsorbant, which produces the acceptable desired purification.

I now propose the use of statistical methods and /or combinatorial chemistry to solve the problem. Thus although the problem has been long in existence, such a method has not been described and is not part of the common knowledge of those skilled in the art of purification.

The basis for the method---taking several reagents and mixing together—is normally very limited because as often as the reagents will react with the substrate, they will react with each other. It has long been known however that polymeric reagent do not have this problem. This has been shown most clearly with organic functionalized polymers (used in Wolf/lamb reactions) but it can be inferred to be equally true with inorganic polymers such as carbon, silica, fluorisil and alumina) for example. As a consequence the effects of polymers on the removal of impurities from a dissolved sample should be purely additive. The dissolved substrate will move around between the two insoluble adsorbants with each adsorbant removing what it has attraction for from the solution. Since the one polymers cannot one invade the pores of the other, they cannot interact with each other.

This being so, it should be possible to perform a trial separation to purify an organic chemical dissolved in a solvent by mixing the sample with a mechanical mixture of adsorbents such as( Norit A, Sarco KB, Celite, silica gel, alumina, reverse phase silica, clay, strong acid ion exchange resin, strong base ion exchange resin, macroreticular resin, florisil, EDTA salts, unfunctionalized DEG cellulose, calcium chloride, manganese chloride, lithium bromide or calcium bromide to name a few. Obviously certain simpler combinations would be better to test. If upon filtration of the sample and reanalysis of the residue the offending impurity has been removed or substantial reduced in a relative sense the job is simply to deconvolute to discover the element or simple combination of adsorbant elements that has the effective action. If there is no appreciable effect, there is a good likelihood that none of the members of the combination are excellent at the impurity removal. Another combination of candidate adsorbants and another condition of solvent, temperature and time is tried until a useful positive result is identified.

It should be realized that macroscopic properties of the solvent medium such as pH will have their own interactions with each of the adsorbents.

For many years my research teams have combined Norit A and Darco KB for the purpose of checking on the ability of these carbons to decolorize slightly impure products. This is my only experimental evidence that this methodology will work. Just theoretically it makes sense.

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• Pamoates or Embonates: crystalline Pharmaceutical Salts or Derivatives for Isolation and Purification
• Symmetrical Bis-N,N-(3-nitrophenyl)urea: A Super Co-crystal Former that might have applications in Product Purification.
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• Sulfate Pharmaceutical Salts
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• Kilomentor weighs in as “Pharmaceutical Manufacturing Goes Green”.
• Another Way to Separate Phenolics by Crystallizing of Co-crystals?
• The Complete Blog for the Preparation of Pharmaceutical Salts
• Inverted Filtration: A chemical synthesis laboratory technique particularly helpful at 5-10 litre scales.
• Recovering More Product by Crystallization in Organic Synthesis:Trituration with a Modified Water Phase as a Potential Chemical Process Development Method
• Kilomentor moves the discussion from Steam Distillation to other Co-distillations

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