High-efficiency liquid chromatography, liquid chromatography, liquid-solid chromatography fixed phase and flow phase.

related topics . Liquid phase
chromat spectrum
and gas chromatography technology high-efficiency liquid chromatography fixed phase and flow phase 1, fixed phase high-efficiency liquid chromatography fixed phase to withstand high pressure capacity classification, can be divided into rigid solids and hard glue two categories. Rigid solids are based on silicon dioxide and can withstand high pressures of 7.0×108 to 1.0×109Pa, and can be made into particles with different diameters, shapes and porosity. If a variety of function groups are bonded on the surface of silicon dioxide, the application can be expanded, and it is one of the most widely used fixed phases. Hard glue is mainly used in ion exchange and dimensional displacement chromatography, it is made of polystyrene and xylene styrene cross-linked. The maximum pressure tolerance is 3.5×108Pa. Fixed phase is classified by pore depth and can be divided into surface porous type and full porous fixed phase..1. Surface porous fixed phaseits substation is a solid glass ball, covering the outside of the glass ball with a layer of porous active materials, such as silicone, silicone oxide, ion exchanger,
molecules
sieve, polyamide, etc. This kind of fixed phase porous layer thickness is small, shallow hole, relatively small dead volume, out of peak rapid, column efficiency is also high; Due to the thin thickness of the porous layer, the maximum allowable amount is limited..2. The fully porous fixedconsists of silicone particles with a diameter of 10nm. This kind of fixed phase because the grain is very fine (5 to 10 m), the hole is still shallow, the transfer rate is fast, easy to achieve high efficiency, high speed. Ideal for complex mixture separation and trace analysis.2. Flow phase Because the flow phase in the high-efficiency liquid chromatography is a liquid, it has affinity to the parts and participates in the competition of fixed relative parts, therefore, the correct choice of flow phase directly affects the separation of the parts. The requirements for mobile phase solvents are:(1) solvents must have the right polarity and good selectivity for the sample to be tested.(2) solvent matches the detector. For UV absorption detectors, attention should be paid to selecting detector wavelengths that are longer than the UV cut-off wavelengths of solvents. The so-called solvent's ultraviolet cut-off wavelength refers to when radiation less than the cut-off wavelength passes through the solvent, the solvent produces a strong absorption of this radiation, at which point the solvent is considered optically nottransparent, it seriously interferes with the absorption measurement of components. For the relection rate detector, it is required to select a solvent with a large difference with the part recering rate as the flow phase, in order to achieve the highest sensitivity.(3) high puritydue to the high sensitivity of high-efficiency liquid chromatography, the purity of mobile phase solvents is alsohigh requirements. Unsoolt solvents can cause baseline instability or create "pseudo-peaks".(4) good chemical stability(5) low viscosity (moderate viscosity) if the use of high viscosity solvents, is bound to increase pressure, not conducive to separation. Commonly used low-viscosity solvents are acetone, methanol and acetylene, etc., but low-stick solvents should not be used, such as penane and ether, they are easy to form bubbles in
-spectrum columns
or detectors, affecting separation.
liquid - solid chromatography . The fixed phase of the liquid solid chromatography is a solid adsorbent. Adsorbents are porous solid particulate matter, and the properties of the atoms, ions, or molecules located on their surface are different from those of the internal atoms, ions, or molecules. The keys of the surface are disturbed by the lack of a mulum structure. Therefore, the surface is generally at a higher energy level, there are some dispersed surface-active adsorption centers. Therefore, the liquid solid chromatography is separated according to the difference of the adsorption capacity of each part on the fixed phase, so it is also known as the liquid solid adsorption chromatography. The ability of the adsorbent to absorb the sample mainly depends on the surface area and the chemical and chemical properties of the adsorbent, the composition and structure of the sample and the nature of the enchantment. When the properties of the parts and adsorbents are similar, they are susceptible to adsorption, showing high retention values, and when the molecular structure of the parts is adapted to the rigid geometry of the surface activity center of the adsorbent, it is easy to absorb. Thus, the adsorption chromatography becomes an effective means of separating geometric isomers, and different function groups have different adsorption energy, so the adsorption chromatography can be separated by family
compound
. Adsorption chromatography is not selective to the same family (i.e. less selective to the molecular weight) and cannot be used to separate compounds with different molecular weights. first, liquid solid chromatography fixed phase liquid solid chromatography using solid adsorbents according to its properties can be divided into polarity and non-polarity two types. Polar adsorbents include silicone, alumina, magnesium oxide, magnesium silicate, molecular sieve and polyamide. Non-polar adsorbents are most commonly activated carbon. Polar adsorbents can be further divided into acidic adsorbents and alkaline adsorbents. Acid adsorbents include silicone and magnesium silicate, alkaline adsorbents include alumina, magnesium oxide and polyamide. Acid adsorbents are suitable for separating alkalis such as fat and aromatic amines. Alkaline adsorbents are suitable for isolating acidic solutes such as phenols, pyridine and pyridine derivatives. Among the various adsorbents, the most commonly used adsorbents are silicone, followed by alumina. In modern liquid chromatography, silicone not only serves as a liquid-solid adsorption chromatography fixed phase, but also as a carrier of liquid-dispensing chromatography and a base of bonded chromatography
filler
. III, liquid-solid adsorption chromatography flow phase liquid chromatography flow phase must meet the following requirements: (1) can dissolve the sample, but can not react with the sample. (2) and fixed do not dissolve each other and do not react irreversibly. (3) viscosity should be as small as possible in order to have high permeability and column efficiency. (4) should match the detector used. For example, when using UV detectors, agents do not absorb UV light. (5) easy to refine, purify, toxicity is small, not easy to catch fire, the price is as cheap as possible. In the liquid-solid chromatography, the basic principle of selecting the flow phase is that the polar sample uses a more polar flow phase, while the polarity is small and the low polar flow phase is used. In order to obtain the suitable solvent polarity, two, three or more different polar solvents are often used to mix and use gradient ehuding if the sample parts are distributed more widely than the k-value range.
liquid chromatography method is . Liquid chromatography is also known as liquid distribution chromatography. In the liquid chromatography, one liquid phase is used as the flow phase, while the other phase is stained as a fixed phase on a very fine inert carrier or silicone. The flow phase and fixed corresponding are insoluble, there should be a clear interface between the two. The process of distributing chromatography is similar to solvent extraction by two insoluble liquids
a
in a liquid funnel. Like the gas-liquid distribution chromatography, the total result of this distribution balance leads to differential migration of the various parts, resulting in separation. An allocation factor (K) or an allocation of a smaller than (k) part, with a small reserved value, flowing out of the bar first. However,
the gas chromatography
, the type of flow phase has a greater impact on the distribution coefficient. , fixed phase, liquid chromatography of the fixed phase is composed of carriers and fixed liquid. There are several commonly used carriers: (1) surface porous carriers (thin shell microbead carriers), consisting of solid glass balls with diameters of 30 to 40 m and porous outer layers with thicknesses of approximately 1 to 2 m. (2) full porous carrier, made of silicone, diatom soil and other materials, diameter of 30 to 50 m porous particles. (3) full porous particle carrier, consisting of nm-grade silicone particles, also known as stacked silicone beads. This carrier has a particle size of 5 to 10 m. Due to the small particles, so the column efficiency is high, is currently the most widely used one of the carriers. because of the liquid chromatography, the flow phase participates in the selection of the action, the flow phase polarity of small changes, will make the reserved value of the parts appear a large difference. Therefore, in the liquid chromatography, only a few different polarity of the fixed liquid can be required. For example, oxydipropanylene (ODPN), polyethyl glycol (PEG), octane (ODS) and horn sorbitane fixation fluids, etc. II, flow phase in the liquid chromatography, in addition to the general requirements, but also requires the flow of relatively fixed phase solubility as small as possible, so the nature of the fixed liquid and flow phase is often in two extremes, for example, when the choice of fixed liquid is a polar substance, the selected flow phase is usually a very small polar solvent or non-polar solvent. Liquid chromatography with polar substances as fixed phase and non-polar solvents as flow phase, called positive phase distribution chromat
ography, is
suitable for separating polar compounds;
.