A tissue processing apparatus for processing biological tissue. The tissue processing apparatus comprises a measurement probe that includes two measurement surfaces spaced apart from each other, wherein the measurement probe is configured to be inserted into a reagent receptacle so that the two measurement surfaces are at least partially immersed in reagent contained in the reagent receptacle. The tissue processing apparatus is configured to use the two measurement surfaces of the measurement probe to obtain at least one electrical measurement of reagent contained in the reagent receptacle before reagent is taken out from the reagent receptacle by the tissue processing apparatus. The tissue processing apparatus is configured to determine, based on the at least one electrical measurement, a concentration and/or a type of reagent contained in the reagent receptacle.