The authors propose a monitoring method for defining metal content in the biological structures, such as plant leaves, tissue samples of animal origin, human skin, etc. The authors used dielectric barrier discharge (DBD) in air at atmospheric pressure as a diagnostic medium. According to the research, at the optimal selection of gas discharge parameters it will not have destructive effect on tissues of biological structure. Indeed, generation of chemically active particles in the plasma will be minimal one. The dielectric barrier separates the investigated sample from the electrode of the discharge system. DBD activation proceeds at frequencies close to the sound range (not more than 15 kHz). It was due to the requirement of ionic component emission only from cells on the surfaces of the structures under study. The conditions of low thermal effect of atmospheric pressure plasma on plant and animal sample provide the choice of DBD frequency range.