A method for monitoring the performance of an analyzer (1; 1') for biological samples having an automated preparation device, the method comprising: receiving an instruction that a monitoring procedure shall be executed; after receipt of the instruction that a monitoring procedure shall be executed: obtaining, by the automated preparation device, at least two quality control ingredients (21; 22, 23; 24) from a repository including a plurality of quality control ingredients (21; 22, 23; 24); mixing, by the automated preparation device, the at least two quality control ingredients (21; 22, 23; 24) in a sample preparation receptacle (3; 7) to obtain a quality control (31; 32; 33) which mimics the properties of a biological sample to be analyzed by the analyzer (1; 1'); the method further comprising: determining at least one parameter of the quality control (31; 32; 33); and determining a status of the analyzer (1, 1') based on the determined parameter of the quality control (31; 32; 33), wherein one of the at least two quality control ingredients (21; 22, 23; 24) is a matrix and a second one of the quality control ingredients (21; 22, 23; 24) is a modifying agent, characterized either in that: the modifying agent includes one or more of a drug, a metabolite of a drug, and a substance that accumulates in a predetermined medical or metabolic condition, or in that: the matrix is derived from blood plasma or is an artificial substance mimicking properties of blood plasma or blood serum. receiving an instruction that a monitoring procedure shall be executed; after receipt of the instruction that a monitoring procedure shall be executed: obtaining, by the automated preparation device, at least two quality control ingredients (21; 22, 23; 24) from a repository including a plurality of quality control ingredients (21; 22, 23; 24); mixing, by the automated preparation device, the at least two quality control ingredients (21; 22, 23; 24) in a sample preparation receptacle (3; 7) to obtain a quality control (31; 32; 33) which mimics the properties of a biological sample to be analyzed by the analyzer (1; 1'); the method further comprising: determining at least one parameter of the quality control (31; 32; 33); and determining a status of the analyzer (1, 1') based on the determined parameter of the quality control (31; 32; 33), wherein one of the at least two quality control ingredients (21; 22, 23; 24) is a matrix and a second one of the quality control ingredients (21; 22, 23; 24) is a modifying agent, characterized either in that: the modifying agent includes one or more of a drug, a metabolite of a drug, and a substance that accumulates in a predetermined medical or metabolic condition, or in that: the matrix is derived from blood plasma or is an artificial substance mimicking properties of blood plasma or blood serum. obtaining, by the automated preparation device, at least two quality control ingredients (21; 22, 23; 24) from a repository including a plurality of quality control ingredients (21; 22, 23; 24); mixing, by the automated preparation device, the at least two quality control ingredients (21; 22, 23; 24) in a sample preparation receptacle (3; 7) to obtain a quality control (31; 32; 33) which mimics the properties of a biological sample to be analyzed by the analyzer (1; 1'); the method further comprising: determining at least one parameter of the quality control (31; 32; 33); and determining a status of the analyzer (1, 1') based on the determined parameter of the quality control (31; 32; 33), wherein one of the at least two quality control ingredients (21; 22, 23; 24) is a matrix and a second one of the quality control ingredients (21; 22, 23; 24) is a modifying agent, characterized either in that: the modifying agent includes one or more of a drug, a metabolite of a drug, and a substance that accumulates in a predetermined medical or metabolic condition, or in that: the matrix is derived from blood plasma or is an artificial substance mimicking properties of blood plasma or blood serum. determining at least one parameter of the quality control (31; 32; 33); and determining a status of the analyzer (1, 1') based on the determined parameter of the quality control (31; 32; 33), wherein one of the at least two quality control ingredients (21; 22, 23; 24) is a matrix and a second one of the quality control ingredients (21; 22, 23; 24) is a modifying agent, characterized either in that: the modifying agent includes one or more of a drug, a metabolite of a drug, and a substance that accumulates in a predetermined medical or metabolic condition, or in that: the matrix is derived from blood plasma or is an artificial substance mimicking properties of blood plasma or blood serum. the modifying agent includes one or more of a drug, a metabolite of a drug, and a substance that accumulates in a predetermined medical or metabolic condition, or in that: the matrix is derived from blood plasma or is an artificial substance mimicking properties of blood plasma or blood serum.