Polyamide is widely used for the separation of botanical extracts (natural products) with phenolic and polyphenolic groups.
Polyamide has a high adsorption capacity due to its swelling properties – much higher than silica gel, alumina, PSDVB, and most other sorbents currently available. This swelling property makes best suited for preparative chromatography. It can also be used for the analysis of phenolic and polyphenolic substances in natural products.
As has been mentioned, Polyamide chromatography is commonly used for the isolation and identification of natural substances with phenolic and polyphenolic functional groups such as flavonoids, anthocyanins, anthoxanthines, anthraquinones, flavones, flavonols, isoflavones, and the like. Through modification of adsorption and partition effects, the retention characteristics of polyamide can be varied substantially.
Due to the medium polarity of polyamide the stationary phase (polyamide swollen with eluent) can be used with mobile phase that is more polar or less polar. It is possible to develop in two dimensions with normal and reversed phase chromatography using the same stationary phase. Adsorption depends on: (1) the number of the polar groups, (2) the degree of the H-bonding activities, (3) size of the analytes, and (4) shape of the analytes. Thus, structural isomers can be well separated on polyamide.

Catalog #/DescriptionAdd to Cart/List Price
26520-025 - Polyamide for CC, <70um, 250gAdd to Cart  226.50
26530-025 - Polyamide for CC, 50-160um, 250gAdd to Cart  226.50
26540-1 - Polyamide for CC, 100-300um, 1kgAdd to Cart  744.15
Cat. #ProductPart. Dist.Size
26500-025Polyamide for TLC2-20 µm250 g
26500-1Polyamide for TLC2-20 µm1 kg
26520-01Polyamide for Flash Chromatography<70 µm100 g
26520-025Polyamide for Flash Chromatography<70 µm250 g
26520-1Polyamide for Flash Chromatography<70 µm1 kg
26530-01Polyamide for Classic Column Chromatography50-160 µm100 g
26530-025Polyamide for Classic Column Chromatography50-160 µm250 g
26530-1Polyamide For Classic Column Chromatography50-160 µm1 kg
26530-5Polyamide For Classic Column Chromatography50-160 µm5 kg
26540-01Polyamide for Process100-300 µm100 g
26540-1Polyamide for Process100-300 µm1 kg

Typical Applications:
Phenols, Aromatic Nitro and Amino Compounds
Chalcones, Chinones, Flavones, and Anthraquinones
Anthocyanins, Anthoxanthines
DNP-Amino Acids
Carbonic Acids and their Amides
Sulfonic Acids and their Amides

Polyamide is often used for thin layer chromatography (TLC) due its well established track history in separation of phenols and phenolic compounds. Polyamide chromatography of phenols and carboxylic acids is possible due to the reversible formation of strong hydrogen bonding between substances and eluents and the peptide groups of the polyamide. The eluents and substances compete for the hydrogen bonds, and this phenomenon creates a situation where the substances can act as an eluent once a hydrogen bond between substrate and adsorbent is established. The elution is a simple displacement process: for phenols the following absolute series was found: water > methanol > acetone > dilute sodium hydroxide solution > formamide > DMF. The high elution strength of dimethylformamide (DMF) may be partially due to the presence of an amide (-CO-N) groups which can form strong hydrogen bonds with the phenolic substances in the form as polyamide.

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For More information about Polyamide for TLC, see our TLC Adsorbents Page

The affinity for polyamide increases in the series phenol, resorcinol, phloroglucinol, however, it decreases in the series phenol, pyrocatechol, pyrogallol. As a rule of thumb, one can say that a second or third hydroxyl group in m or p position of an aromatic hydrocarbon increases the adhesion to polyamide, while in o position it decreases the bonding. In resorcinol and hydroquinone obviously both hydroxyl groups can simultaneously interact with two different amide bonds of the polyamide resulting in a stronger retention of the compounds compared to phenol. The hydroxyl groups of the pyrocatechol on the contrary have to compete for the same amide group.

The second hydroxyl group strengthens the affinity for the usual aqueous eluent and thus additionally increases the migration speed. A partial saturation by intramolecular hydrogen bonds also may be important. Besides the number and position of the hydroxyl groups of an aromatic compound, the eluent has an important effect on the affinity of a phenol for polyamide. Depending on the ability of a solvent, it may compete with the hydrogen bonds between polyamide and phenol, or, develop its own interactions with the compound in question and then rapid desorption will occur.

The desorption ability increases in the following sequence: water < methanol < acetone < diluted sodium hydroxide solution < formamide < dimethylformamide. The high elution strength of the dimethylformamide is probably due to the fact, that it possesses a -CO-N group itself and can thus form the same interactions with phenolic substances as the polyamide, i.e. it is the strongest hydrogen acceptor.

The chromatography of phenolic compounds on polyamide has been frequently applied for the isolation and structure determination of different natural products. Carboxylic acids are also bonded to polyamide via hydrogen bonds. The affinity for monocarboxylic is still low. Dicarboxylic acids and aromatic acids are retained stronger, especially if the aromatic part of the molecule is larger.

Strong affinity for polyamide is found with numerous aromatic nitro compounds. The interaction between the nitro compound and polyamide corresponds to a reaction of a Lewis acid with a base. This is why separations of aromatic nitro compounds on polyamide can be considered as ion exchange. For this reason elution in sharp bands requires an eluent with good buffering properties. This principle has been successfully applied for the separation of dinitrophenylamino acids-which are formed in the determination of amino terminals of peptides and proteins-on polyamide columns.

Quinones are irreversibly bonded to polyamide due to the free amino groups of the adsorbent.

The hydrophilic adsorbent polyamide 6 (Nylon 6 = Perlon = Σ- aminopolycaprolactame) is available with or without fluorescent indicator.