[Photometric micro-determination of the residues of disinfectant quaternary ammonium compounds in milk. 3. Improvement and adaption for milk products (author's transl)].

The photometric method for the quantitative micro-determination of the residues of quaternary ammonium compounds (QAC) in milk was improved. The casein has proved as an essential interfering substance and it was largely eliminated. Furthermore the bond of QAC on casein in discussed. The minimum level für determination for QAC in milk was reduced to 0.2 ppm. By modifying the photometric method for some milk-products as cream, joghurt, and quarge QAC can be determined at minimal concentrations of 1 ppm.