Classification and Development of High Pressure Infusion Pumps in Ion Chromatography

The high-pressure infusion pump is an important part of the ion chromatograph. It feeds the active phase to the separation system and allows the sample to complete the separation process in the column system. High pressure pumps for ion chromatography should have the following properties:

(1) Flow stability: The flow accuracy is usually required to be about ± 1% to ensure the repetition of storage time and the accuracy of qualitative and quantitative analysis.

(2) There is a certain output pressure, ion chromatography generally works at 20 MPa, slightly lower than high performance liquid chromatography.

(3) Corrosion resistance to acids, bases, and buffers. Unlike high performance liquid chromatography, all eluents in ion chromatography contain acids or bases, and pumps should be made of fully plastic Peek materials.

(4) Small pressure fluctuations, convenient replacement of solvents, small dead volume, ease of cleaning and replacement of solvents.

(5) The flow rate is optionally within a certain range and can meet certain accuracy requirements.

(6) Some infusion pumps have a gradient elution function.

At present, the reciprocating plunger pump is widely used in ion chromatography, and only the low-pressure ion chromatography uses a peristaltic pump. However, the peristaltic pump can withstand too little pressure and problems may arise in the actual operation.

Due to the high reciprocating frequency of the plunger of the reciprocating plunger pump, the wear resistance of the seal ring and the rigidity and accuracy of the one-way valve are all very high. The seal ring is generally made of PTFE additive material, and the ball, seat and plunger of the one-way valve are made of artificial gem material. Reciprocating pumps have single and double plungers. In general, the double plunger flow is more stable and the pulsation is small, but the structure is complicated and the price is relatively high.

High-performance liquid chromatography using stainless steel or titanium alloy material, compared with high-performance liquid chromatography, ion chromatography pump is a fully plastic system, thus the acid, alkali, salt anti-pollution properties, and to ensure the determination of the metal ions The correctness.

1. The single piston pump takes some necessary measures such as adding a damper, special design of the cam profile and the use of advanced electronic technology to obtain satisfactory results. Early ion chromatography and some simple ion chromatographs often used single plunger pump systems.

2. Double-plunger pump The double-plunger pump, which uses two pump heads in parallel, uses a 180° phase difference to reduce pressure and flow fluctuations. Therefore, the double-plunger pump can directly enter the separation system without a damper and can perform low-pressure gradient elution. Most high-end ion chromatographs now use double-plunger pumps.

At present, the latest type of microporous ion chromatograph has a 2mm internal diameter, which is 1/4 of the cross-section of a conventional 4mm internal diameter column. Therefore, under the condition that the linear velocity is constant, the flow rate is conventional. One-fourth of the chromatogram, so it uses the pump's flow rate is 0.01 ~ 2.50ml/min. Its main feature is that the plunger is relatively small, but its structure is similar to that of a conventional ion chromatograph. Due to the reduced flow rate, the amount of solvent can be greatly reduced. If the sample is injected in the same amount, the sensitivity can be increased by 4 times.