What are the Properties of Liquid Chromatography Columns?
The liquid chromatograph is divided into liquid-liquid chromatography and liquid-solid chromatography depending on whether the stationary phase is liquid or solid. The modern liquid chromatograph consists of a high-pressure infusion pump, a sample introduction system, a temperature control system, a column, a detector, and a signal recording system. Compared with classical liquid chromatography equipment, it is characterized by high efficiency, rapidity and sensitivity. The mixture of high boiling, hard gas compounds is passed through the chromatographic core eluent and is separated. Used in biochemistry, biomedicine, environmental chemistry, petrochemical and other sectors.
The liquid chromatograph packing may be directly composed of a matrix such as silica gel, alumina, styrene-divinylbenzene or methacrylate having a high degree of crosslinking, etc., or may be coated or chemically bonded on the basis of these substrates. Liquid to form.
The performance of the LC column is as follows:
Di-alumina is similar to silica gel, but is more unstable to aqueous solutions and acidic alkaline aqueous solutions. Therefore, it is rarely used as a matrix for the bonded stationary phase, and it is also suitable for separating polar, weakly polar, non-strongly dissociated compounds dissolved in an organic solvent, especially for separating aromatic hydrocarbons. Acidic acid-dissociable compounds in liquid chromatography tend to form dead adsorption on alumina. In addition, the ability of alumina to separate geometric isomers is superior to that of silica gel.
Silica gel is a ceramic matrix of inorganic nature, which is rigid and not easily deformed. The chemical properties are relatively stable, but it is still unstable for aqueous solutions, especially alkaline aqueous solutions. Even if the surface is subjected to good chemical bonding and covers the fixing solution, it is necessary to pay attention to the dissolution of silica gel by water, alkaline solution and acidic solution, matrix or It is said that the effect of column bed dissolution on the column is fatal. Silica-based fillers constitute the vast majority of liquid chromatography column packings. The liquid chromatograph pure silica gel packing is suitable for separating polar, weakly polar non-strongly dissociated compounds dissolved in organic solvents. Silica gel can also be used for gel chromatography but has low column efficiency. The high-pressure liquid phase filler of the silica matrix-bonded stationary phase has high separation efficiency unmatched by other fillers.
3. Polymer filler
The polymer matrix deforms under pressure, with low pressure limits but a wide pH range. The liquid chromatograph styrene-divinyl phenyl is highly hydrophobic and uses any mobile phase to stabilize over the entire pH range. The column can be cleaned with strong acids and bases. The liquid chromatograph methacrylate matrix is more hydrophobic than styrene-divinylbenzene, but can be rendered hydrophilic by appropriate functional group modifications. Due to its non-compression and swellability, the polymer filler is suitable for use in macromolecular-like proteins or synthetic polymers, and can also be used as a molecular exclusion or ion exchange column. The macroporous resin which has developed rapidly in recent years is actually a styrene-divinylbenzene polymer or a similar synthetic polymer.