Contactless Conductivity

eDAQ supplies several products for ion chromatography (IC) capillary electrophoresis (CE), and microfluidic channel electrophoresis using Capacitively Coupled Contactless Conductivity Detection (C4D).

The basis of contactless conductivity meaurements is explained in Figures 1, 2, and 3:

 

Fig 1. C4D uses a transmitter electrode to subject a sample region to a large amplitude, high frequency electromagnetic signal. A corresponding, attenuated, AC signal registers at a receiver electrode.

Fig 2. The size of the received signal is affected by the conductivity of the sample.

Fig 3. The received AC signal is deconvoluted to convert the amplitude into a DC analog voltage signal appropriate for data collection.

As analyte ions pass into the detection region they cause small changes to the overall sample conductivity. Continous monitoring of the conductivity signal will show a series of peaks, the areas (or heights) of which are related to analyte concentration. The signal is processed like a conventional chromatogram.

The C4D electrodes do not make direct contact with the sample. Thus they are electrically isolated from the sample (ideal for electrophoresis detection), and electrode fouling is eliminated.

Since the the vast majority of analytes for CE are ionic, a C4D system functions as a 'universal' method of detection requiring minimal sample preparation. The technique can also be used in parallel with UV-visible absorbance, or fluorescent detection. Sensitivity is typically similar to UV-visible absorption detection. Click here for some application areas and here for C4D resources.

eDAQ products for C4D include:

  • C4D Amp (EA120) includes choice of headstage. Requires e-corder or ER281 PowerChrom.
  • C4D Detector (ER125) with analog and serial interface, includes choice of headstage. Can be used with third party data acquisition systems.
  • C4D Head (ET120) headstage for capillary electrophoresis. For use with C4D Amp (EA120) or C4D Detector (ER125).

 
blue border
blank