What is C4D and how does it work?

C4D is an abbreviation for Capacitively-Coupled Contactless Conductivity Detection, it 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. 

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

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

As analyte ions pass into the detection region they cause small changes to the overall sample conductivity. Continuous 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.