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Ion Chromatography System

Ion chromatography system used in laboratory

1. What is ion chromatography system?
    1.1 Ion chromatographic principle
    1.2 Ion chromatographic system working principle
    1.3 Ion chromatographic system working process
    1.4 Ion chromatographic system application
2. Ion chromatographic composition
3. How to buy ion chromatography system?

What is ion chromatography system?

Ion chromatography is a type of high-performance liquid chromatography and is therefore also known as high-performance ion chromatography (HPIC) or modern ion chromatography. Ion chromatography system differs from conventional ion exchange column chromatography systems. It has a resin with high cross-linking and low exchange capacity, a small injection volume, and a plunger pump to deliver the drench solution usually for online automatic continuous conductivity detection of the drench solution.

Ion chromatographic principle

Generally, ion chromatography can be divided into three types: ion exchange chromatography, ion rejection chromatography, and ion pair chromatography.

A. Ion exchange chromatography

Ion exchange chromatography is based on the principle of different forces between ions. It is mainly used for the separation of organic and inorganic anions and cations.

B. Ion repulsion chromatography

Ion repulsion chromatography is based on Donnan row repulsion, which is a separation using non-ionic interactions between solutes and stationary phases. It is mainly used for the separation of weak organic acids and organic acids, but also the separation of alcohols, aldehydes, amino acids, and sugars.

C. Ion pair chromatography

The separation mechanism of ion-pair chromatography is adsorption and separation. The selectivity is mainly determined by the mobile phase. This method is mainly used for the separation of surface-active anions and cations as well as metal complexes.

Ion chromatographic system working principle

The separation principle of ion chromatography systems is based on the reversible exchange between dissociable ions on ion exchange resins and solute ions with the same charge in the mobile phase and the difference in the affinity of the analyte solute for the exchange agent and are separated. It can be applied to the separation of hydrophilic anions and cations.

Ion chromatographic system working process

a. An infusion pump delivers the mobile phase to the analytical system at a steady flow rate (or pressure).

b. The sample is introduced through the injector before the column.

c. The mobile phase carries the sample into the column, where the components are separated and flow sequentially with the mobile phase to the detector.

d. Suppression ion chromatography adds a suppression system before the conductivity detector, i.e., another high-pressure infusion pump is used to deliver the regeneration solution to the suppressor.

e. In the suppressor, the background conductance of the mobile phase is reduced. The effluent is then introduced into the conductivity detection cell and the detected signal is sent to the data system for recording, processing, or storage.

f. Non-suppressed ion chromatographs do not use suppressors and high-pressure pumps to deliver regeneration solution, so the structure of the instrument is relatively much simpler and cheaper.

Ion chromatographic system application

Ion chromatography systems are mainly used for the analysis of environmental samples, including anions and cations in samples such as surface water, drinking water, rainwater, domestic and industrial wastewater, acid precipitates and atmospheric particulate matter, trace impurities in water, and reagents related to the microelectronics industry. In addition, it has a wide range of applications in the fields of food, hygiene, petrochemical, water, and geology.
The common ions that can be detected
The common ions that can be detectedF-, Cl-, Br-, NO2-,PO43-,NO3-,SO42-, formic acid, acetic acid, oxalic acid, etc.
Positive ionLi+, Na+, NH4+,K+, Ca2+,Mg2+, Cu2+, Zn2+, Fe2+, Fe3+, etc.

Ion chromatographic composition

Like HPLC instruments, ion chromatography systems are generally made into individual components, and then the required components are assembled according to the analytical requirements. The most basic components of an ion chromatography system consist of a drenching eluent system, a chromatographic pump system, an injection system, a flow path system, a separation system, a chemical suppression system, and a detection system, and a data processing system.

Ion chromatography parts

A. Drenching eluent system

The common analysis mode of ion chromatography system is the ion-exchange conductivity detection mode, which is mainly used for the analysis of anions and cations. Commonly used anionic eluents include OH and carbonate systems, while commonly used cationic eluents include methane sulfonic acid and oxalic acid systems.

The consistency of the drench solution is essential to ensure the reproducibility of the analysis. To ensure the consistency of the drench solution during the same analysis, a drench solution protection device is added to the drench solution system to adsorb and filter the harmful parts of the air entering the drench solution bottle, such as CO2 and H2O.

B. Chromatography pump

a. Materials
The properties of the drench solution for ion chromatography are acid and alkali solutions. If the drench solution comes in contact with metal, it will cause chemical corrosion. If you choose a stainless-steel pump head, corrosion will lead to pump leakage, poor flow stability and shortened column life, and other problems. The ion chromatography pump head should choose full PEEK material (column normal use pressure is generally less than 20MPa).
b. Type of pump
a) Single plunger pump.
b) Double plunger pump. It can be subdivided into a tandem double plunger pump and a parallel double plunger pump.
c. Pressure pulsation elimination mode
a) Electronic pulsation suppression.
b) pulse damper

C. Injection system

The injection system is the component that switches the sample from the atmospheric state to the high-pressure state. It is an important way to ensure the reproducibility of each working state to improve the reproducibility of the analysis.
a. Inlet valve
The material of the inlet valve is similar to that of the chromatography pump. Choose an inlet valve made of all PEEK to ensure the life of the instrument and the accuracy of the analytical results. Its types can be divided into manual injection valves and motorized injection valves. The feed consistency of the manual injection valve depends on manual operation, and the system integration is poor. The electric injection valve has better injection consistency and high system integration.
b. Autosampler
Autosamplers have the best injection consistency and the best system integration.

D. Flow path system

The flow path system uses special piping, fittings, and other connecting parts for chromatography to ensure all-plastic contamination-free dissolution as well as to guarantee the reliability and longevity of the materials. Materials include PEEK tubing (for high-pressure areas), PTFE tubing, silicone tubing (for gas line or waste liquid), various joints, and connecting parts.

E. Separation system

Separation systems are an important component of ion chromatography. It is also one of the main consumables.
a. Pre-column
Pre-column, also known as in-line filter, is made of PEEK, and its main function is to ensure the removal of particulate impurities.
b. Protection column
The protective column serves the same function as the analytical column packing in that both eliminate impurities in the sample that could damage the analytical column packing. If inconsistent, it will lead to increased dead volume, peak diffusion, and poor separation.
c. Analytical column
The analytical columns are effective in separating the sample components.

F. Chemical suppression system

The suppression system is one of the core components of an ion chromatography system. Its main function is to reduce the background conductance and improve the detection sensitivity. The quality of the suppressor is related to the baseline stability, reproducibility, and sensitivity of ion chromatography and other key indicators.
a. Column-gel inhibition
Inhibition is performed using fixed short columns or in situ filled inhibition gels. Different inhibition columns are used alternately and belong to intermittent inhibition.
b. Ion-exchange membrane inhibition
The ion exchange membrane uses the principle of ion concentration permeation for inhibition. If you need to use an ion exchange membrane for inhibition, you need to prepare sulfuric acid regeneration solution and the system needs to be configured with nitrogen or a power device.
c. Electrolytic self-regenerating membrane inhibition
Electrolytic self-regenerating membrane inhibition utilizes electrolytic water to produce medium ions and ions in conjunction with ion exchange membranes for inhibition. It is the most recommended method among the three.

G. Detection system

The conductivity detector is the most basic and commonly used detector for ion chromatograph systems and follows by the amperometric detector.
a. Conductivity detector
The principle of the conductivity detector is based on the application of limiting molar conductivity. It is mainly used for the detection of inorganic anions and cations, organic acids and organic amines, etc. Conductivity detector can be subdivided into bipolar pulse detector, quadrupole conductivity detector, and five-pole conductivity detector.
Conductivity detectorDescription
Bipolar pulse detectora. Two electrodes are set in the flow path.
b. By applying a pulsed voltage, the current is read at a suitable time for amplification and display.
c. The detector is susceptible to electrode polarization and bilayer.
Quadrupole conductivity detectora. The detector is susceptible to electrode polarization and bilayer.
b. Constant voltage between the two measurement electrodes is maintained in the circuit design.
c. Unaffected by changes in load resistance, inter-electrode resistance, and bilayer capacitance.
d. Electronic suppression function. Supports direct conductivity detection mode as with cation detection.
Five-pole conductivity detectora. The addition of a grounded shield electrode to the quadrupole conductivity detection mode greatly improves measurement stability.
b. Very low noise at high background conductance.
c. Electronic suppression function. Supports direct conductivity detection mode as with cation detection.
b. Amperometric detector
The principle of the amperometric detector is based on the measurement of the magnitude of the electrolytic current. It is mainly used for the detection of substances with redox properties.
a) DC amperometric detection mode
DC amperometric detection mode is mainly used for the detection of ascorbic acid, bromine, iodine, cyanide, phenols, sulfides, sulfites, catecholamines, aromatic nitro compounds, aromatic amines, uric acid, and p-diphenol.
b) Pulse amperometric detection mode
The pulse amperometric detection mode is mainly used for the detection of alcohols, aldehydes, sugars, amines (one, two, or three amines, including amino acids), organic sulfur, mercaptans, thioethers, and thioureas. However, it cannot detect sulfur oxides.
c) Integral pulsed amperometric detection mode
The integral pulse amperometric detection mode is an upgraded detection mode of pulse amperometric detection. This mode is suitable for testing substances with pulsed amperometric detection.

H. Data processing system

The task of the data processing system is to complete the data processing and link the instruments.

How to buy ion chromatography system?

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If you are interested in our ion chromatography system or have any questions, please write an e-mail to [email protected], we will reply to you as soon as possible.

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