Patent ID: 7288767

Claim:
A method of correcting a relative response value for an instrument of the kind capable of determining a constituent of a sample from a predetermined functional relationship between constituents of the sample and a relative response value being a response value from the exposure of the sample to electromagnetic radiation relative to the response value from the exposure of a reference sample to electromagnetic radiation, said method comprising the steps of: when the instrument is in a first state in which it is newly calibrated: obtaining a first response value for a first adjustment sample, and obtaining a second response value for a first reference sample, when the instrument is in a state different from the first state: obtaining a third response value for a adjustment sample having the same composition as the first adjustment sample, obtaining a fourth response value for a reference sample having the same composition as the first reference sample, from the response values, determining a gain representing the relationship between a first relative response value being the ratio between the first and the second response values and a second relative response value being the ratio between the third and fourth response values, respectively, and for a sample, correcting the relative response value by means of the gain in order to determine a constituent of the sample in question, wherein the first reference sample comprises a first substance having a first absorbing characteristic and the first adjustment sample comprises the first substance and a second substance having a second absorbing characteristic.