The eluent system of an ion chromatograph is the driving force behind the separation of samples in the chromatographic column. Its core function is to provide a stable and controllable eluent flow environment for the ion exchange separation process, and to achieve effective separation of different ions through precise delivery of the eluent. This system is mainly composed ofRinsing solution storage bottle、High pressure infusion pumpComposed of auxiliary components such as degassing devices, filters, back pressure regulators, etc., the specific process of each part working together is as follows:
The rinse solution storage bottle is used to store rinse solutions that are suitable for the type of ion being tested. Common rinse solutions include carbonate/bicarbonate solutions (used for anion analysis), methane sulfonic acid solutions (used for cation analysis), etc.
- Liquid storage bottles are usually made of inert materials such as polyethylene and polytetrafluoroethylene to avoid chemical reactions with the rinsing solution or the release of impurity ions, which may affect the detection results.
- The rinsing solution needs to undergo degassing treatment (such as ultrasonic degassing and helium degassing) before use to remove dissolved gases (such as oxygen and carbon dioxide) from the solution, in order to prevent pump pulsation, detector signal fluctuation, or chromatographic peak deformation caused by bubbles entering the flow path.
The high-pressure infusion pump is the core component of the eluent system, responsible for delivering the eluent from the storage bottle to the chromatographic column system at a constant flow rate and pressure. Its performance directly determines the stability of the separation effect.
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Drive TypeThe mainstream is reciprocating plunger pumps (including single plunger pumps and double plunger pumps). Double plunger pumps alternate suction and discharge through two plungers, which can effectively reduce flow pulsation and ensure the stability of the eluent flow rate (flow rate accuracy can usually reach ± 0.1%).
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Pressure and flow rate controlAccording to the specifications of the chromatographic column and separation requirements, the pump can provide high pressure (usually up to 15-30 MPa) and precise flow rate (usually 0.1-5 mL/min). For example, when analyzing common anions, the flow rate is often set to 1.0 mL/min and the pressure is maintained at 10-20 MPa.
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Gradient elution functionPartial high-end infusion pump supportgradient elutionBy program control, the concentration, pH value, or composition of the rinsing solution can be changed (such as mixing different proportions of carbonate and bicarbonate solutions). This method can adjust the elution intensity during the analysis process for ions with large affinity differences to achieve efficient separation of multiple ions in complex samples (such as simultaneous analysis of F ⁻, Cl ⁻, SO ₄ ² ⁻, PO ₄ ³ ⁻ and other anions with different affinity).
The auxiliary components of the rinsing solution system are used to optimize the delivery status of the rinsing solution, avoiding flow path failures or detection interference:
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filterInstalled between the outlet of the liquid storage bottle and the inlet of the pump, with a typical aperture of 0.22 μ m, it is used to filter out small particles and impurities in the eluent, preventing blockage of the chromatographic column or wear on the pump body.
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Degassing deviceIn addition to manual degassing in the early stage, some instruments are equipped with online degassing devices (such as membrane degassing devices), which can remove the gas that dissolves again during the transportation of the rinsing solution in real time, continuously ensuring that there are no bubbles in the flow path.
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Back pressure regulatorInstalled at the end of the flow path (after the detector), stable back pressure is applied to maintain the liquid phase of the eluent in the chromatographic column, while reducing pressure fluctuations in the flow path and improving flow rate stability.
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Pulsation damperIf a single plunger pump is used, it is necessary to use a pulsation damper to absorb the pulsation of the pump, so as to make the flow rate of the eluent more stable and avoid the broadening of chromatographic peaks or retention time drift caused by flow rate fluctuations.
Partial ion chromatography equipmentRinsing solution regeneration deviceThe rinsing solution generator (such as the electrochemical regeneration suppressor) can generate rinsing solution online through electrochemical methods (such as electrolyzing water to produce H ⁺, OH ⁻, reacting with salt solution in the storage bottle to generate rinsing solution), without the need for manual preparation of rinsing solution. At the same time, it can achieve the recycling of rinsing solution, reduce waste liquid generation, and improve analysis efficiency.