A method for automatically detecting biological substances for analyses of samples applied to plates, wherein a) in a magazine, in which a large number of plates are stored, b) a gripper takes hold of one plate in the magazine and delivers it to a measuring head for identification, c) the measuring head identifies the position and the shape of the samples by means of sensors, d) a microprocessor analyzes their position and shape, e) the relative orientation of an extraction head and of a counterpart extraction head with respect to the plate is adjusted by the microprocessor, f) the extraction head and the counterpart extraction head, which form a sealing edge by clamping the plate, the sealing edge spatially tightly enclosing the sample, so that the desired substances, and as little as possible of interfering matrix can be extracted from the sample by having a flushing fluid introduced via an admission line, running through the sample and running off via a discharge line, g) the extraction head and the counterpart extraction head are cleaned of residues, wherein, in order to rinse the extraction head and the counterpart extraction head clean, a flushing fluid is brought into the cavity via admission line, the discharge line or an inlet of an additional wash unit, the flushing fluid remaining there for a desired time before being blown or sucked out with gas via the discharge line or an outlet of the wash unit, h) the measuring head is brought together with the next sample, i) the sequence of the process from c) to h) is repeated with the new sample until all the desired samples on a plate are processed, j) the gripper returns the plate into the magazine, k) the procedure according to b) to j) is repeated until all the desired plates of a magazine are tested, l) after each extraction process according to f, the desired substances and matrix are forwarded for further processing. a) in a magazine, in which a large number of plates are stored, b) a gripper takes hold of one plate in the magazine and delivers it to a measuring head for identification, c) the measuring head identifies the position and the shape of the samples by means of sensors, d) a microprocessor analyzes their position and shape, e) the relative orientation of an extraction head and of a counterpart extraction head with respect to the plate is adjusted by the microprocessor, f) the extraction head and the counterpart extraction head, which form a sealing edge by clamping the plate, the sealing edge spatially tightly enclosing the sample, so that the desired substances, and as little as possible of interfering matrix can be extracted from the sample by having a flushing fluid introduced via an admission line, running through the sample and running off via a discharge line, g) the extraction head and the counterpart extraction head are cleaned of residues, wherein, in order to rinse the extraction head and the counterpart extraction head clean, a flushing fluid is brought into the cavity via admission line, the discharge line or an inlet of an additional wash unit, the flushing fluid remaining there for a desired time before being blown or sucked out with gas via the discharge line or an outlet of the wash unit, h) the measuring head is brought together with the next sample, i) the sequence of the process from c) to h) is repeated with the new sample until all the desired samples on a plate are processed, j) the gripper returns the plate into the magazine, k) the procedure according to b) to j) is repeated until all the desired plates of a magazine are tested, l) after each extraction process according to f, the desired substances and matrix are forwarded for further processing.