Introduction and application of ion chromatography!

The principle of separation is based on the reversible exchange between the dissociable ions on the ion exchange resin and the solute ions of the same charge in the mobile phase and the difference in affinity of the analyte solute to the exchanger. Suitable for hydrophilic anions and cations

For example, the separation of several anions, after the sample solution is injected, first directly exchange ion exchange with the ion exchange position of the analytical column (that is, retained on the column), such as using NaOH as the eluent to analyze the F- in the sample. Cl- and SO42-, the anion remaining on the column is replaced by the OH-group in the eluent and eluted from the column. Analyte ions with weak affinity for the resin are eluted in advance of the analyte ions with strong affinity for the resin. This is the ion chromatographic separation process. The eluate passes through the chemical suppressor to suppress the background conductance from the eluent to *small. Thus, when the analyte leaves the conductivity cell, there is a large, accurately measurable conductance signal.

Like a typical HP LC instrument, current ion chromatographs are typically made up of individual cell components, which are then combined according to analytical requirements. *The basic components are mobile phase vessels, high pressure infusion pumps, injectors, columns, detectors and data processing systems. In addition, mobile phase on-line degasser, autosampler system, mobile phase suppression system, post-column reaction system, and fully automatic control system can be configured as needed.

The working process of the ion chromatograph is: The infusion pump delivers the mobile phase to the analytical system at a steady flow rate (or pressure). The sample is introduced through the injector before the column, and the mobile phase carries the sample into the column. The components are separated and flowed to the detector in sequence with the mobile phase. Suppression-type ion chromatography adds a suppression system before the conductivity detector, ie, another high-pressure infusion pump delivers the regeneration fluid to the suppressor, at the suppressor The background conductance of the mobile phase is reduced, and the effluent is then directed to the conductance detection cell, and the detected signal is sent to the data system for recording, processing or storage. The non-suppressed ion chromatograph eliminates the need for a suppressor and a high pressure pump that delivers regenerant, so the structure of the instrument is relatively simple and the price is much cheaper.

Probable process: The high pressure infusion pump delivers the mobile phase to the analytical system at a steady flow rate (or pressure). The sample is introduced through the injector before the column, and the mobile phase carries the sample into the column. It is separated and flows to the detector in sequence with the mobile phase. Suppressed ion chromatography adds a suppression system in front of the conductivity detector, which uses another high pressure infusion pump to deliver the regenerant to the suppressor. In the suppressor, the mobile phase background conductance is reduced, the flow is then directed into the conductivity cell, and the detected signal is sent to a data processing system for recording, processing, or storage. The non-suppressed ion chromatograph does not use a suppressor and a high pressure pump that delivers regenerant, so the instrument structure is relatively simple and relatively inexpensive.

Ion Chromatography is mainly used for the analysis of environmental samples, including cations and cations in samples such as surface water, drinking water, rainwater, domestic sewage and industrial wastewater, acid sediments and atmospheric particulate matter, and traces of water and reagents related to the microelectronics industry. Analysis of the amount of impurities.

In addition, it is widely used in food, health, petrochemical, water and geology.

Anions: F ^- , Cl ^- , Br ^- , NO ^{2 -} , PO ₄ ^3- , NO ^{3 -} , SO ₄ ^2- , formic acid, acetic acid, oxalic acid, etc.

Cations: Li ⁺ , Na ⁺ , NH ^{4 +} , K ⁺ , Ca ^{2 +} , Mg ^{2 +} , Cu ^{2 +} , Zn ²⁺ , Fe ²⁺ , Fe ^{3+ ,} and the like.

Ion chromatograph separation and determination of common anions is its expertise, a sample of one shot is taken, the results of 7 common ions can be obtained within about 20 minutes, which is impossible to achieve by other analytical methods. Chromatography did not show superiority compared to AAS and ICP methods.

1, ion chromatography separation

Ion chromatography separation is mainly based on the principle of ion exchange. Ion exchange resin with low exchange capacity is used to separate ions. It is widely used in ion chromatography. Its main filler type is organic ion exchange resin.

2, ion pair chromatography

The stationary phase of ion-pair chromatography is a hydrophobic neutral filler, and the counter ion used for anion separation is an alkylamine such as tetrabutylammonium hydroxide or cetyltrimethane hydroxide. The counter ion used for cation separation is an alkyl sulfonic acid such as sodium hexane sulfonate, sodium heptane sulfonate or the like.

3. Ion exclusion chromatography

Ion exclusion chromatography, mainly based on the Donnon membrane repulsion effect: the ionized component is not preserved by rejection, while the weak acid is made by a certain preservation principle. Ion exclusion chromatography is mainly used to separate organic acids and inorganic oxyacids such as borate, carbonate and sulfate, organic acids and the like.

4, the application of ion chromatography

Detection of inorganic anions; detection of inorganic cations and analysis of organic anions and cations, mainly including analysis of biogenic amines, organic acids and sugars.