Fast and low-cost online detection of critical micelle concentration based on impedance spectroscopy

The dosage of detergents in washing processes is decisive for efficiency. The optimal dosage can be determined by a measurement of the critical micelle concentration (CMC). Classical methods are not suitable for online applications in washing machines with automatic dosage because detergent concentrations cdet highly above the CMC are also needed and automatic dosage cannot be stopped in time. Optical methods are commonly used for such applications but they are expensive or imprecise. A new online detection method of CMC using impedance spectroscopy (EIS) is developed. Impedance values at selected frequencies are used to detect ccmc. The new method detects the CMC immediately and precisely when ccmc is reached so that automatic detergent dosing can be stopped in time and online measurement is possible.