Ion chromatography
Ion chromatography (IC), also known as ion-exchange chromatography, is a highly precise analytical separation technique that separates ions based on their charge, thereby enabling their detection and quantification in liquids. As a key method in analytical chemistry, it is used for the reliable determination of charged compounds in samples.
Table of contents
- How does ion chromatography work?
- This is what Quality Analysis can do for you
- Ion-exchange chromatography in detail
- Practical applications
- Summary
How does ion chromatography work?
Ion chromatography is based on the principle that the ions in the sample displace their counterions in the eluent. However, these ions do not remain stationary, instead they are in turn displaced by their counterions due to the continued addition of eluent. The eluent then flushes them to the detector, by means of which the eluent's specific peaks can be identified. The sample's peaks are compared to peaks for known standards.
Ion chromatography
this is what Quality Analysis can do for you
- Qualitative and quantitative evaluation of ionic contamination on printed circuit boards and electronic assemblies (IPC-TM-650 2.3.28)
- Verification of inorganic ions
- Routine checks on process water, cleaning baths, electroplating baths, water-mixed cooling lubricants
- Analytics in battery research/recycling
The evaluation is undertaken in accordance with established standards such as IPC TM-650 or in accordance with you own, customer-specific standards.
In a dialogue with you, our experts find the most reliable, quickest and most economical method to answer your question reliably and unambiguously. We compile all our results in a detailed test report that provides you with practical answers.
We would also be pleased to analyse your sample at short notice.
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The IC System: Structure and Workflow
An IC system is the complete instrument used for ion chromatography. It consists of several core components that work seamlessly together to precisely analyze ions. These include the pump, which transports the mobile phase through the entire system. The selection of the eluent (e.g., carbonate or hydroxide eluents for anions, or diluted acids for cations) is specifically tailored to the ions being separated and determines the separation conditions within the column. The injector then introduces the sample into the eluent stream.
Separation column, suppressor, and detector
The sample then enters the separation column, whose stationary phase is often made of a specialized polymer resin. This is where the actual separation takes place: ions migrate through the column at different speeds depending on their interaction with the stationary phase. After the column, a suppressor reduces the background conductivity of the eluent and enhances detection sensitivity before the separated ions reach the conductivity detector. The detector records their signals, which are then transmitted to a computer for data acquisition and evaluated as a chromatogram.
Cation and anion chromatography
A key feature of ion chromatography is its flexibility in adapting to the type of ions being analyzed. A distinction is mainly made between cation chromatography and anion chromatography. Depending on the separation column used, the stationary phase carries functional groups with defined charges: negatively charged groups bind cations, while positively charged groups bind anions. This allows positively charged ions (cations) and negatively charged ions (anions) to be selectively separated and subsequently quantified.
High-performance liquid chromatography (HPLC)
In high-performance liquid chromatography (HPLC), the substances to be analyzed are efficiently separated under high pressure and can be precisely identified and quantified using standards. To identify an unknown substance, its retention time is typically compared with that of a known standard. Quantification is carried out by comparing the peak areas of the sample with those of standards of known concentration, usually via a calibration curve, enabling reliable determination of the analyte concentration.
Practical application of ion-exchange chromatography
Ion chromatography is used in numerous areas for the verification of contamination. In particular, ionic contamination can be separated particularly well into its individual substances using this method which is why it is a commonly used method for ensuring technical cleanliness verification. However, the method is also valuable in water analytics such as during the detection of undesirable leachates, for example nitrite.
Semiconductor industry
The semiconductor industry is continuously challenged to control ionic contaminants, particularly at trace levels, as these can significantly impair the functionality and reliability of components. Ion chromatography is a key analytical method for the selective determination of such ionic contamination.
In contrast to aggregate parameters, it enables specific single-ion analysis, allowing individual anions and cations (e.g., chloride, sulfate, or sodium) to be separated and quantified.
Electroplating industry
Ion chromatography is an established analytical technique in the electroplating industry. It enables the routine monitoring of plating bath composition, which is critical to ensuring the quality of the final products.
Furthermore, reaction products and contaminants—such as inorganic anions, organic acids, or additive degradation products—can be analyzed with high precision. This supports process optimization and helps to prevent defects.
In summary: Ion chromatography
Ion chromatography is based on the exchange of ions with a positive or negative charge. A polymer resin is used as a stationary phase, while as a rule the mobile phase is an ammonium salt compound (for the separation of anions) or a sulphonic acid (for the separation of cations).