An ion chromatography (IC) system typically consists of a liquid eluent, high-pressure pump, sample injector, guard column, analytical column, suppressor, conductivity detector, and data collection system. The Dionex Inuvion IC System provides additional accessories that may change or optimize the instrument configuration.

Before running a sample, the IC system is calibrated using a standard solution. The standard solution is normally diluted across the expected concentration range of the sample that is analyzed to create a calibration curve. By comparing the data obtained from a sample to that obtained from the standard calibration curve, sample ions can be identified and quantitated. The data collection system, typically a computer running chromatography software, produces a chromatogram (a plot of the detector output vs. time). The chromatography software converts each peak in the chromatogram to a sample concentration and generates a report. A typical IC analysis consists of six stages.

Figure Ion chromatography process analysis
  1. Eluent delivery
  • Eluent is a liquid that carries the sample through the ion chromatography system. The Dionex Inuvion IC System uses either manually prepared eluent or an eluent generator cartridge to generate eluent online from deionized water.
  • Dionex Inuvion IC Systems enabled for Reagent Free Ion Chromatography (RFIC) use an eluent generator cartridge (Thermo Scientific™ Dionex™ Eluent Generator (Dionex EGC) to automatically generate high-purity potassium hydroxide, carbonate, bicarbonate, or methanesulfonic acid (MSA) eluents electrolytically. Systems using a Dionex EGC can operate in two eluent delivery modes. In isocratic mode, the eluent concentration remains constant throughout the run. The system with RFIC also supports multi-step linear gradient methods (up to nine steps) by using a Dionex EGC to change the eluent concentration over time. The delivery mode is defined in the Chromeleon CDS Instrument Method Wizard. For more information, refer to the Chromeleon CDS Help.
  • Sample injection
    • The sample is loaded into a sample loop manually or automatically (if an automated sampler is installed). When triggered, the Dionex Inuvion IC System injects the sample into the eluent stream.
    • The pump pushes the eluent and sample through the guard and analytical columns (chemically inert tubes packed with a functionalized polymeric resin). The guard column, shorter than the analytical column but with the same functionalization, filters and retains contaminants that could potentially clog or passivate the analytical column.
  • Separation
    • As the eluent and sample are pumped through the analytical column, the sample ions are separated. In the Dionex Inuvion IC System, the mode of separation is called ion exchange. This mode is based on the premise that different sample ions migrate through the IC column at different rates, depending upon their interactions with the ion exchange sites.
  • Suppression
    • After the eluent and sample ions leave the column, they flow through a suppressor that selectively enhances detection of the sample ions while suppressing eluent conductivity.
  • Detection
    • The conductivity cell within the conductivity detector measures the electrical conductance of sample ions as they emerge from the suppressor and produces a signal based on a chemical or physical property (for example, the charge) of the analyte.
  • Data analysis
    • The conductivity detector transmits the signal to a data collection system.
    • The Chromeleon CDS, the data collection system for the Dionex Inuvion IC System, identifies the ions based on retention time and quantifies each analyte by integrating the peak area response. The data is quantified by comparing the sample peak areas in a chromatogram from a calibration curve produced from a set of standard solutions. The results are then displayed as a chromatogram, allowing for the automatic determination and tabulation of ionic analyte concentrations.