A specimen analysis apparatus for determining a concentration of a target material in a specimen, comprising: a cartridge, comprising at least two containers, each container containing a reagent configured to react with the target material in the specimen to measure the concentration of the target material, wherein each reagent further includes a predetermined concentration of internal standard material containing the target material, wherein the internal standard material is configured to release the target material while being dissolved during a process of mixing with the specimen and wherein the concentrations of the internal standard materials in the reagents of the at least two containers are different; an optical detector unit for detecting optical characteristics from a reaction between the target material in the specimen and the released target material in the internal standard materials with the reagents in the at least two containers and providing optical signal values; a controller configured to: derive a measured calibration curve from an extent of a change in the optical signal value of the target material measured in the at least two containers; characterized in that the controller is further configured to: obtain, from identification information provided on the cartridge and/or from information about the property of the reagent stored in a memory of the apparatus, a factory calibration curve indicating a predetermined extent of a change in the optical signal value of the target material in the at least two containers; determine, based on a comparison of the measured calibration curve with the factory calibration curve, a correction value for calculation of the concentration of the target material; and determine a corrected concentration of the target material based on the correction value. a cartridge, comprising at least two containers, each container containing a reagent configured to react with the target material in the specimen to measure the concentration of the target material, wherein each reagent further includes a predetermined concentration of internal standard material containing the target material, wherein the internal standard material is configured to release the target material while being dissolved during a process of mixing with the specimen and wherein the concentrations of the internal standard materials in the reagents of the at least two containers are different; an optical detector unit for detecting optical characteristics from a reaction between the target material in the specimen and the released target material in the internal standard materials with the reagents in the at least two containers and providing optical signal values; a controller configured to: derive a measured calibration curve from an extent of a change in the optical signal value of the target material measured in the at least two containers; characterized in that the controller is further configured to: obtain, from identification information provided on the cartridge and/or from information about the property of the reagent stored in a memory of the apparatus, a factory calibration curve indicating a predetermined extent of a change in the optical signal value of the target material in the at least two containers; determine, based on a comparison of the measured calibration curve with the factory calibration curve, a correction value for calculation of the concentration of the target material; and determine a corrected concentration of the target material based on the correction value. derive a measured calibration curve from an extent of a change in the optical signal value of the target material measured in the at least two containers; characterized in that the controller is further configured to: obtain, from identification information provided on the cartridge and/or from information about the property of the reagent stored in a memory of the apparatus, a factory calibration curve indicating a predetermined extent of a change in the optical signal value of the target material in the at least two containers; determine, based on a comparison of the measured calibration curve with the factory calibration curve, a correction value for calculation of the concentration of the target material; and determine a corrected concentration of the target material based on the correction value. obtain, from identification information provided on the cartridge and/or from information about the property of the reagent stored in a memory of the apparatus, a factory calibration curve indicating a predetermined extent of a change in the optical signal value of the target material in the at least two containers; determine, based on a comparison of the measured calibration curve with the factory calibration curve, a correction value for calculation of the concentration of the target material; and determine a corrected concentration of the target material based on the correction value.