Next, the commercial solutions with

Next, the commercial solutions with internal standard added were quantified on the basis of the developed models. The mean content of diclofenac sodium found in the studied preparations from the PLS models was in the 24.7–25.8 mg/mL (24.7–25.3 mg/mL) range based on spectra normalised by the intensity at maximum and in the 24.5–25.7 mg/mL (24.8–25.2 mg/mL) range based on spectra normalised by the integrated intensity of the acetonitrile νs(CN) band. Applying PCR models, these values were found to be in the 24.6–25.6 mg/mL (24.9–25.5 mg/mL) and 24.5–25.7 mg/mL (24.6–25.3 mg/mL) range, respectively. As in the case of unnormalised spectra results obtained from calibration models optimised for the each medicine studied are quoted in parentheses. Although the calibration parameters for univariate models were unsatisfactory, concentrations of the API found applying them were not very different from the real values, but once more quantification errors were unacceptably high (Table 3).