What are the main types of high performance liquid chromatography（HPLC）instruments?

Liquid-solid adsorption chromatography

1.1 Separation principle Liquid-solid chromatography is a mixture separation based on the difference in adsorption capacity of each component, and the stationary phase is a solid adsorbent.

1.2 stationary phase; adsorption chromatography stationary phase can be divided into two major categories of polar and non-polar.

1.3 mobile phase; mobile phase requirements:

1.3.1 The solvent selected should be incompatible with the fixation and maintain the stability of the column.

1.3.2 The solvent selected should have high purity to prevent the accumulation of trace impurities in the column, causing changes in column performance.

1.3.3 The selected solvent properties should be matched with the detector used. If an ultraviolet absorption detector is used, the solvent with UV absorption at the detection wavelength cannot be used. If a refractive index detector is used, gradient elution cannot be used. .

1.3.4 The solvent selected should have sufficient solubility in the sample to improve the sensitivity of the measurement.

1.3.5 The solvent chosen should have a low viscosity and a suitably low boiling point.

1.3.6 Avoid using solvents with significant toxicity to ensure the safety of workers

1.4 Application Liquid-based chromatography is based on the surface adsorption capacity, so it is often used to separate compounds with different polarities, and also to separate samples with the same polarity groups, but in different numbers.

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Liquid-liquid partition chromatography

1.1 Separation principle; The principle of partition chromatography is the same as the liquid-liquid extraction, which is the law of distribution.

1.2 Stationary phase The partition chromatography stationary phase consists of two parts, one part being an inert carrier and the other part being a fixing solution coated on an inert carrier.

1.3 mobile phase; in the internal chromatography, the mobile phase is required to be as non-miscible as possible with the fixed solution

1.4 Application; can separate polar compounds and separate non-polar compounds. Due to the presence of different polar bonded phases, the selectivity of the separation is well controlled.

Bonded phase chromatography

1.1 Separation principle 1.1.1 Positive-bonded phase separation chromatography separation: the use of polar bonds and immobilization, the separation mechanism of solute on such stationary phase belongs to the distribution chromatography.

1.1.2 Reverse Bonded Phase Chromatography Separation principle: The use of a less polar bonded stationary phase, the separation mechanism can be explained by the theory of solvophobic effect.

1.2 stationary phase; according to the size of the polarity can be divided into non-polar, weak polarity, polar chemical bonding stationary phase three.

1.3 Mobile phase 1.3.1 In the positive-bonded phase chromatography, a mobile phase similar to the reversed-phase liquid-liquid partition chromatography is used, and the main component of the mobile phase is hexane or heptane.

1.3.2 In reversed-phase bonded phase chromatography, the mobile phase uses a mobile phase similar to the reversed-phase liquid-liquid partition chromatography with the subject of water.

1.4 Application 1.4.1 Application of positive-bonded phase chromatography: mostly used to separate various polar compounds such as dyes, explosives, dopamine, amino acids, etc.;

1.4.2 Application of anti-bonded phase chromatography: Due to its simple operation, good stability and repeatability, this method has become a general-purpose liquid chromatography method. It has been widely used and developed in many fields such as biochemistry, medical research, food analysis and environmental pollution analysis.

Gel chromatography

Gel chromatography, also known as size exclusion chromatography, is a chromatographic method that separates in order of molecular size. The stationary phase gel of gel chromatography is a porous polymeric material with a certain shape and stability. Depending on the mobile phase used, gel chromatography can be divided into two categories: gel filtration chromatography (GFC) using a mobile solvent as a mobile phase and gel permeation chromatography (GPC) using a mobile phase using an organic solvent such as tetrahydrofuran. .