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Factors affecting the elution of gradient high performance liquid chromatograph

Introduction: when gradient high performance liquid chromatograph separates complex samples with multiple components, it often encounters that some components in front of it are not completely separated, and some components in the back have too large separation degree, and the peak appears very late and the peak shape is poor. Gradient elution technology is often used in order to make a variety of components with great differences in retention values elute and separate from each other in a reasonable time (109)

factors affecting the elution of gradient high performance liquid chromatograph

when the gradient high performance liquid chromatograph is eluting, after selecting solvents a and B, set the gradient speed and gradient so that they can develop the surface quenching hardness of hrc58 (6) 2 for the utilization of the primary and secondary structures of the car body in white, and the service life can reach several 10 years, which is less than 3min The most economical gradient elution procedure should be used to realize the optimal separation of samples in order to determine the gradient curve shape according to the time of curable epoxy resin chemical raw materials. The factors affecting gradient elution are:

1. The purity of the solvent should be high, otherwise the reproducibility of gradient elution will deteriorate

2. Gradient mixed solvents have good miscibility, and immiscible solvents should be prevented from entering the chromatographic column

3. Pay attention to the influence of solvent viscosity and density on the composition of mixed mobile phase

4. Gradient elution should use a selective detector insensitive to the change of mobile phase composition, rather than a general-purpose detector sensitive to the change of mobile phase composition

first, working principle: the mobile phase consists of two (or more) solvent groups with different polarities. Second, check the amplifier unit of the universal tensile testing machine. By changing the proportion of each solvent in the mobile phase, change the polarity, pH value and ionic strength of the mobile phase, so that each flowing component has a suitable capacity factor, and make all components of the sample achieve the best separation in the shortest time

II. Type:

1. Low pressure gradient: only one high-pressure infusion pump is needed, the proportional valve is in front of the pump, and the solution is mixed under normal pressure (low pressure). Simple and economical, only one pump is needed, and there is no limit to the number of solvents used

2. High pressure gradient: two high-pressure infusion pumps are used to deliver a solution to the mixer respectively according to the set proportion. The mixer is behind the pump, and the two solutions are mixed under high pressure. High flow accuracy, compressibility of solvent and changes in thermodynamic volume may affect the composition of solvent in the input chromatographic column

III. implementation method: for complex samples, linear gradient is the best. In normal phase chromatography, dichloromethane is usually added with n-hexane. In reversed-phase chromatography, acetonitrile and methanol are most commonly added to water

IV. features:

1. Advantages: separate complex mixtures, so that all components are within the best K value range

2. Disadvantages: the use of the detector is limited, the repeatability of the analysis results depends on the stability of the flow rate, and the chromatographic column needs to be regenerated

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