Separation by Partition

Halomycins. The halomycins are a group of four antibiotics produced by M.icromonospora halophjtica and separated by partition chromatography on Chromosorb W coated with formamide (19). Further purification was accompHshed using preparative dc (212). 

Liquid chromatography is complementary to gas chromatography because samples that cannot be easily handled in the gas phase, such as nonvolatile compounds or thermally unstable ones, eg, many natural products, pharmaceuticals, and biomacromolecules, are separable by partitioning between a Hquid mobile phase and a stationary phase, often at ambient temperature. Developments in the technology of Ic have led to many separations, done by gc in the past, to be carried out by Hquid chromatography. 

As a result, there is a growing trend to off-line clean reverse-pulse filters by using bags with multiple compartments. These sections allow the outlet-gas plenum serving a particular section to be closed off from the clean-gas exhaust, thereby stopping the flow of inlet gas. On the dirty-side of the tube sheet, the isolated section is separated by partitions from the neighboring sections where filtration continues. Sections of the filter are cleaned in rotation as with shaker and reverse-flow filters. 

These drugs are ionized at this high pH, and therefore the separation is obtained due to a combination of both partitioning and electrophoresis. It is also possible to use a microemulsion buffer at a low pH where the acids will be unionized and separated by partitioning only. Microemulsion at pH 12 was used to determine the log P value of acidic solutes in their unionized form (30). 

Among many methods proposed for hydrophobic partition, only the method of Shanbhag and Axelsson (1975) is described here. The principle of this method is phase separation by partitioning the hydrophobic upper phase (palmitate is used as it is the most abundant saturated fatty acid in food fat) and the hydrophilic lower phase of proteins. A protein will be separated more into the top layer when it is hydrophobic. The method used by Keshavarz and Nakai (1979), based on Shanbhag and Axelsson (1975), is described in this protocol. 

The nature of the chromophore was deduced by the Zurich group (102) by a careful study of the borohydride reduction of IVa-methylfluoro-curarine. Reduction of a very dilute solution of this quaternary salt in phosphate buffer at pH 8, with an excess of sodium borohydride, gives a substance (LXXXIII) with a pure a-methyleneindoline chromophore in acid solution, this product (LXXXIII) is rapidly and irreversibly converted into a second substance with a typical indoline UV-spectrum. The nature of these products and their relationship will be considered subsequently. When the same reduction is attempted on a preparative scale, with a higher concentration of reactants, the pH cannot be kept below 9, and the product contains both a-methyleneindoline and indoline components. Acidification of the reaction mixture gives a mixture of substances, all of which have the UV-spectrum of an indoline the mixture can be separated by partition chromatography into three crystalline quaternary compounds (LXXXIV, LXXXV, and LXXXVII). 

The capacity of carbon columns is high, and a wide range of substances, from unsubstituted to fully methylated sugars, can be fractionated successively in the same run. The separation of isomers can sometimes be improved by the addition of borate to the eluant, according to the method devised by Barker and coworkers. Mixtures that are difficult or impossible to separate by partition chromatography can often be resolved on carbon columns. Since the reverse is often true, the methods supplement each other. 

Razina, I. S., Viktorova, M. E. Determination of submictogram amounts of osmium and ruthenium after separation by partition paper-chromatography. Metody AnaL Redkometal. Mineral. Rud. Gom. Rorod. 1, 53 (1971) C. A. 80, 33 582w (1974)... 

In most cases, PGs or their derivatives are separated by partition chromatography on reversed-phase columns using gradients of organic solvents and water with in-... 

The differential distribution of solutes between two immiscible liquids is the basis for separation by partition chromatography (see Figure 6-3). Operationally, one of the... 

G. Protoberberbine Alkaloids.—Alkaloids from Fumaria officinalis which were difficult to separate by partition chromatography and counter-current distribution were separated by the dependable method of column chromatography.190... 

Carry out a rough polarity separation by partitioning the extract between hep-tane/methanol, CH2Cl2/water, or n-BuOH/water prior to VCC, or,... 

The methylated polymer is isolated and hydrolyzed, and the partially methylated monomers are characterized. Originally these derivatives were separated by partition chromatography on paper (Binkley, 1955), but this requires a relatively large amount of material. Subsequently the methylated monomers were separated by GLC as their methyl glycosides (Bishop, 1964), trimethylsilyl derivatives (Petersson and Samuelson,... 

In general, HPLG refers to liquid chromatography employing reversed-phase columns. It is most commonly used for the determination of hydrophobic compounds. After injection, compounds are separated by partitioning between the reversed-phase column surface and the eluent, usually a solvent buffer mixture. Separation is typically followed by UV or fluorescence detection. Numerous publications describe HPLG in theory and practice. 

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