C4D for Ion Chromatography with the ET125 Headstage

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Figure 1. ET125 Headstage on 1/16th inch tubing after the column
Figure 2. Chromatogram of 1mM anions

The eDAQ C4D system was connected directly to 1/16th inch tubing for IC/HPLC and used to detect six anions.


The eDAQ ET125 General Purpose C4D Headstage is a contactless conductivity detector for ion chromatography (IC) and high-performance liquid chromatography (HPLC) instruments. It is designed to connect directly to tubing sizes 1/8 inch (3.2 mm) OD or less (the users specifies the OD when ordering the product). For example, the 1/16th inch (1.6 mm) outer diameter headstage connects directly to the standard for tubing for IC and HPLC.

Connecting the detector immediately after the separation column, as shown in Figure 1, greatly reduces extra-column band broadening (remixing of the analytes after the column) because the “dead volume” is reduced.

A sample containing 1 mM fluoride, chloride, nitrate, bromide, pyruvate and nitrate was analysed; the chromatogram is shown in Figure 2.

The method used was similar to experiments previously published, except contactless (as opposed to contact) conductivity detection was used: Separation of anions by ion-interaction chromatography with a novel cationic/zwitterionic eluent; Zhu Yan, Ling Yanyan, James S. Fritz, Paul R. Haddad; Journal of Chromatography A, 1020 (2003) 259–264

Equipment Required


  • Sample: A solution of 1 mM fluoride, chloride, nitrate, bromide, pyruvate and nitrate, dissolved in water.
  • Buffer: 98.75% water, 1.25% methanol, 2.5mM tetrabutylammonium hydroxide (TBAOH) and 5mM 3-(N-morpholino)-propane sulfonic acid (MOPS).
  • Separation column: Macherey-Nagel, Nucleosil 120.5 C18, part 720041.46.
  • C4D settings
    • frequency = 800 kHz
    • amplitude = 80 A
    • headstage gain OFF.
  • Data recording:
    • lowpass Filter = 10 Hz
    • range = 20 mV
    • sampling rate = 1000 data points per second.