Vol. 13, Issue 6 (2025)

Beer’s Law provides a foundational relationship in analytical chemistry, linking absorbance with the concentration of a solute through the molar extinction coefficient (?). This study explores the validity of Beer’s Law for various Cr(VI) complexes and determines their (?) values under different pH conditions using UV-Visible spectrophotometry. Cr(VI), typically present as chromate (CrO?²?) or dichromate (Cr?O?²?) ions, exhibits charge-transfer absorption bands that vary with pH and coordination environment. By preparing aqueous Cr(VI) complexes in the presence and absence of organic ligands such as quinic acid and MDTC, we investigated how ligand binding and pH influence( ?)max and (?). Calibration curves constructed from absorbance data at characteristic wavelengths (350-373 nm) showed strong linearity (R² > 0.995) over defined concentration ranges, affirming the applicability of Beer’s Law within these limits. (?) values determined were in good agreement with literature: ~1500-1600 M?¹ cm?¹ at 350 nm under acidic conditions and ~180-190 M?¹ cm?¹ at 372 nm under basic conditions. Deviations from linearity at higher concentrations were attributed to inner filter effects and species interconversion. The findings highlight the importance of pH control and ligand environment in spectrophotometric quantification of Cr(VI). This work not only confirms previously reported (?) values but also emphasizes the role of speciation in analytical accuracy. The data serve as a reference for future studies involving Cr(VI) detection and environmental monitoring.