A catalyst system for removing one or more components from a fluid stream includes a binder layer and a plurality of catalyst structures affixed to, and protruding from, the binder layer such that the catalyst structure surface is directly exposed to the fluid stream. In a preferred embodiment, conditions that indicate the progress of the treatment on a real time basis are monitored, and the timing of the initiation of the termination process is additionally based on the calculated amount of treatment and treatment rate of the process in progress. The aim of the invention is to develop and improve said method in such a way that it supplies reliable, reproducible results for the recording of neuro-toxic substances in the blood plasma of an individual, in particular in the case of encephalopathic conditions, such as for example hepatic failure, or of coma conditions of various origins. The conductive portion is electrically biased during polishing to reduce the edge effect that tends to occur with conventional electrochemical mechanical processing systems.