Continuous determination of the alumina content for the electrolytic production of aluminium

Since aluminium oxide is the raw material of the electrolysis process in the production of aluminum, when it comes to controlling the electrolytic pots, it's essential to regulate the aluminium oxide content of the bath.

However, the current method of regulating aluminium oxide content is based on a rough estimate, as there is no sensor for continuous monitoring that is reliable and sufficiently economical for industrial use.
Continuous measurement of the aluminium oxide content would radically change the regulation method, which would lead to a better tank performance.

We are looking for tools and/or methods to estimate the aluminium oxide content or professionals who are currently developing such a method. 
Any considered methods will have to be compatible with the electrolyte used: a very corrosive, cryolite-based molten salt, maintained at a temperature around 1000 °C.

Up to now, we have considered an electrochemical method based on impedance spectroscopy (in the lab), but it is difficult to transfer this method to an industrial setting.