Simultaneous spectrophotometric determination of iron (II) and copper (II) in tablets by chemometric methods

The significant spectral overlap (Di) 0.5 = 0.5667 which is about 75.3% overlapping of the UV/Visible absorption spectra of iron (II) and copper (II) complexes necessitates chemometric assisted methods for simultaneous analysis of these ions in the pharmaceutical mixture. These metal ions were analyzed simultaneously by UV/Visible spectrophotometric method where 8-hydroxyquinoline was used as a chromogenic reagent. The absorption spectra were recorded in the wavelength range of 350-600 nm digitized at 1 nm. Four chemometrics methods such as first derivative spectrophotometry (1D zero crossing), first derivative ratio (1D ratio), classical least squares (CLS) and principal component regression (PCR) were used to predict the concentrations of the metal ions. For the derivative spectrophotometry, measurements were made at two selected wavelengths. The calibration curves were linear in the range of 2-12 μg/ml for both ions. For classical least squares and principal component regression, the calibration model was obtained and predictions of the unknown concentrations of the ions in the synthetic mixtures and in the dosage form were done. The accuracy and the precision of these methods were determined by calculating the % recovery and the relative standard errors correspondingly. The methods were successfully applied for analyzing synthetic mixtures and commercial pharmaceutical preparation.