1.1.3. Reactions rotor and reading. biosystems A15

Service manual

1.1.3. Reactions rotor and reading

The preparations are dispensed in an optical quality methacrylate reactions rotor thermos tated at 37ºC. The optical absorbance readings are taken directly on this rotor. Each reaction can be read for 10 minutes. The readings are taken as they are programmed in each measurement procedure. The reaction wells have been designed to enable the mixture of the sample and the reagent during the dispensing. Each rotor has 120 reaction wells. The length of the light path is 6 mm. The minimum volume required to take the optical reading is 200 uL. The wells have a maximum useful capacity of 800 uL. When the reactions rotor is completely full, the user must change it for one that is empty, clean and dry. The reactions rotors can be reused up to 5 times if they are carefully cleaned immediately after use.

The Cleaning the semi-disposable reactions rotor section in the Installation and maintenance manual describes how to cle an the rotors. The us er has a test in the computer programme, which he or she may use to check the condition of the rotor. The rotor is driv en by a step-by-step motor with a transmission. A Peltier system with PID control thermostates the rotor at 37ºC.

An optical system integrated in the rotor takes the readings directly on the reaction wells. The light source is a 10 W halogen lamp. The detector is a silicon photodiode. The wavelength is selected by a drum with 9 positions available for optic filters. The filters are easily ch an ged by the user from the exterior of the analyser, without the need for disassembling the filter drum. A step-by-step motor positions the drum. The optical system is capable of taking 1.25 readings per second, with or without a filter change in between. The light beam from the lamp passes through a compensated interferential filter to select the desired wavelength. It then passes through the rotor well and finally reaches the photodiode, where the light signal is turned into an electric signal. A sophisticated analogical digital integrator-converter system converts the electric signal into a digital value with which the analyser obtains the absorbance values. The optical system continues to work when the general cover of the ana lyser is open, whereby the analyser can continue to take readings while the user handles, for example, the sample tubes or the reagent bottles. The rotor cover must be in place for the optical system to work correctly.

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