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Liquid Chromatography: The difference between a binary high pressure gradient and a quaternary low pressure gradient!

Liquid Chromatography Binary Two-Pump, High Pressure Mixing, Insensitive to Air Bubbles
Four yuan only one pump, low pressure mixing, more sensitive to bubbles, must be equipped with online degasser
A major difference between the binary high-pressure mixing and the four-element low-pressure mixing is that the former is mixed immediately after entering the infusion pump and the latter is slowly mixed after the pump is introduced, and some even have to pass through a mixer, and the mixing is not only behind, but also the effect is not as good as former.
High Pressure Gradient Many pumps can now be used to control another pump. Low pressure gradients often require a gradient control system.
Several pumps, divided into high-pressure mixing and low-pressure mixing, high-pressure mixing, also called pump mixing, hplc several yuan pump is several pumps; low pressure mixing is also called pump mixing, in fact, is a pump, a few dollars is to install a few solenoid valve
The pump can be assembled as a binary high pressure gradient and a quaternary low pressure gradient. The two differences are as follows:
Binary high pressure gradient:
Configuration: Double Pump + Inline Mixer
Working mode: Double pumps are connected in parallel and can have two mobile phases at the same time. Enter according to a preset proportion, and then mix under high pressure. The mixing ratio is more accurate, it is not easy to generate bubbles, and it is not necessary to repeatedly clean in order to change the mobile phase. Work efficiency. Gradient elution can be done at the same time. When the components of the sample to be tested are complex and the components in the sample cannot be completely separated with a fixed mobile phase ratio, a gradient elution is required. In the same analysis process, the instrument automatically changes the mobile phase match. In contrast, the elution of the last inseparable substance in the sample gives the effect of separate peaks in the same spectrum. Helps to increase the accuracy of analysis and avoid missing important substances.
Hplc quaternary low pressure gradient:
Configuration: single pump + low pressure gradient valve + online degasser + mixer
Working mode: Up to four mobile phases can enter the flow path at the same time. Mixing according to the preset ratio, it is easy to produce bubbles due to mixing under normal pressure. Therefore, an online degasser must be equipped to eliminate the influence of air bubbles. Gradient elution can be done, after setting on the instrument, in the same sample analysis project, after a certain period of time, according to the ratio set by the user to change the mobile phase matching ratio, to separate all the components in the sample, there are Helps improve analysis accuracy.
For simple analysis, general compounds use a binary system that is very good, analysis if you do protein, peptide semi-preparative or gradient elution or quaternary system is convenient, but need to be equipped with online degasser. Through these years I The experience, I think, is still four yuan, if the funds are no problem.
The so-called few yuan refers to the number of flow paths that can be controlled at the same time. One, two, and four yuan have low-pressure pumps, such as Waters 515 - a low pressure, waters1515 - binary low pressure, HP1100 - four yuan low pressure. The high-pressure pump is mostly binary, so it is too expensive to do it up again, and its practicality is not strong. Because the binary high pressure can generally meet the needs of customers, such as watersUPLC. Low pressure pump usually has only one pump, more than two yuan can do gradient elution, is mixed first, after the degassing machine through the online degassing pump, and the high pressure pump For a few dollars, there are several pumps. After the pump is mixed, the flow rate is controlled to match the ratio, and air bubbles are not easily generated, but there is still a degasser.
The binary high-pressure gradient flow control has higher precision, the mixing chamber has high pumping efficiency and high gradient mixing accuracy after pumping; the four-element low-pressure gradient system uses a single pump plus gradient proportional valve because the proportional valve is in front of the pump. , And the solvent of each flow channel is mixed together in the proportional valve, so it is the pre-pump, low-pressure mixing. In general, the quaternary low-pressure gradient can also meet the requirements for routine analysis; if the analysis sample composition is complex, the reproducibility requirement is high, or the gradient analysis needs to be performed at low flow, the high pressure gradient is better.
Liquid chromatography from the performance comparison: Binary high pressure is certainly due to the four yuan low pressure. The binary high pressure mixing ratio is obtained by changing the flow rate of the pump. Usually the pump flow rate is very accurate, so the precision of the mixing is also very high. The mixing ratio of the four-element low-pressure gradient is controlled by controlling the opening and closing time of the solenoid valves of different flow paths. The theoretically-mixed ratio is also accurate, but in reality, there is a delay in the opening and closing of the solenoid valve regardless of how it operates. Fast, it still takes a little time. For example, A and B are each 50% mixed. In the unit of time, the electromagnetic valves of A and B are opened for 50% of the time. The problem is not significant at this time. The delay effect of the solenoid valve can be compensated as much as possible by adjusting the compensation coefficient. . However, if the situation is extremely extreme, 99% of the A road and 1% of the B road, in this case, the electromagnetic valve of the A road opens 99% of the time, and the B road only accounts for 1%. The time is very short. When the delay of the B-way solenoid valve is greatly affected, it may even be delayed for longer than the working time. The result can be imagined. The high pressure gradient will not have this problem.
From the price comparison: In general, the price of the binary high pressure gradient will be much higher than the four-element low pressure gradient (if the other configurations are the same).
Binary pumps usually refer to high pressure gradients, and quaternary pumps refer to low pressure gradients. High pressure refers to the fact that the two pumps deliver liquid separately in the mixing chamber behind the pump, while the low pressure relies on the switching of solenoid valves to deliver the pump in different phases. It is also mixed in the mixing room behind the pump. The main difference is that the low pressure mixing is easy to produce bubbles. The high pressure is not easy to produce bubbles. Low pressure should pay attention to cleaning, especially when using buffer salt, to avoid blocking the solenoid valve feeding pipeline.

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