Contactless Conductivity Introduction

eDAQ supplies several products for Capacitively-Coupled Contactless Conductivity Detection (C4D). C4D can be used for:


Please see the full list of C4D products.


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.

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 to view citations and C4D resources.

The C4D electrodes do not make direct contact with the sample. CONTACTLESS conductivity detection has several advantages over CONTACT conductivity detection:

  • The sample doesn't come into contact with the detector electrodes so it is easy to analyse hazardous, corrosive or radioactive liquids. There is no carryover or memory effect from the previous sample. There is no electrode deterioration or polarization.
  • The C4D provides an electrically isolated measurement, which means it won't interfere with other measurements being done in the same liquid.
  • Very small sample volumes can be used, less than 20 nanolitres is possible.



This page was last modified on: 10 Jan 2018 16:41:00