The invention provides a module being connectable to a mating connector having a tube and including a case and a connector. First a platelet rich plasma and a platelet poor plasma are formed by centrifuging a quantity of anticoagulated whole blood that was previously drawn from the patient. Further, in a state where the pre-spectroscope is located at its zero-order light position, the main spectroscope is rotated to detect the angular position of the main spectroscope for the predetermined wavelength. The first method takes advantage of the surface-independent nature of the CO2 absorption reactions in a homogeneous aqueous system.