APPLICATION OF DIFFUSE-REFLECTANCE INFRAR ED-SPECTROSCOPY FOR THE QUANTITATIVE-DETERMINATION OF INORGANIC-COMPOUNDS .2. INVESTIGATION AND REDUCTION OF THE MEASUREMENT ERROR

Concentration dependence of the errors in diffuse reflectance IR Fouri er transform spectroscopy (DRIFTS) was investigated. Theoretical mathe matical models were developed and experimentally controlled. It has be en found that the relative error in DRIFTS measurements can increase u p to 30-100% if the sample concentration is < 0.1-0.2 m/m %. Therefore , the precision and the reliability of the method should be increased as follows: 1. The uncertainty of the determination of the sample refl ectance should be decreased by parallel measurements on the samples an d the calibration standards (multiple calibration). 2. The uncertainty of the determination of the reference reflectance (R(infinity,r)) sho uld be excluded by measuring all the samples and the calibration stand ards against one and the same sample of reference. 3. If R(infinity,r) < 1, the experimentally obtained K-M functions should be modified by the exact value of R(infinity,r), otherwise the method is distorted by systematic error.