Simultaneous determination of palladium(II) and nitric acid in nitric acid medium using chemometric-assisted UV-visible spectroscopy

Pd(II) and nitric acid were simultaneously determined over the concentration ranges of 60–444 ppm and 1.5–6.0 M, respectively. The measurements were performed using UV–Vis absorption spectrophotometry. Since the absorption signals were influenced by both palladium and nitric acid concentrations, advanced chemometric tools were applied to analyze the complex multivariate data. In the present study OPLS assisted PCR approach was used for simultaneous quantification of Pd(II) and nitric acid. For nitric acid estimation, spectral data were preprocessed using mean normalization followed by OPLS-PCR modeling. The developed method can quantify Pd(II) in the concentration range 60–444 ppm without prior knowledge of nitric acid concentration. Nitric acid can also be quantified in the range 1.5–6.0 M. To ensure reliable quantification, chemometric regression models were developed and validated with different sets of validation samples. Additionally, an independent test dataset was used to confirm the robustness of the models. Overall, the developed chemometric method provides accurate and reliable simultaneous determination of Pd(II) and nitric acid in nitric acid media. The method achieved model estimated LOD values of 18.14 ppm for Pd(II) and 0.45 M for nitric acid, with corresponding LOQ values of 60.48 ppm and 1.50 M, respectively, demonstrating adequate sensitivity for quantitative analysis over the investigated concentration ranges. The proposed method is rapid, accurate, and reagent-free, thereby minimizing the generation of secondary analytical waste associated with the use of chromogenic reagents. The method may be potentially suitable for online monitoring after calibration and validation using representative process matrices.