Evaluation of Perrhenate Spectrophotometric Methods in Bicarbonate and Nitrate Media

2-pyridyl thiourea and methyl-2-pyridyl ketoxime based perrhenate, Re(VII), UV-vis spectrophotometric methods were evaluated in nitrate and bicarbonate solutions ranging from 0.001 M to 0.5 M. Standard curves at [Re]=2.5-50 mg L^-1 for the Re(IV)-thiourea and the Re ketoxime complexes were constructed at 405 nm and 490 nm, respectively. Detection of limits for N-(2-pyridyl) thiourea and methyl-2-pyridyl ketoxime methods in ultrapure water are 3.06 mg/L and 4.03 mg/L, respectively. Influences of NaHCO₃ and NaNO₃ concentration on absorbance spectra, absorptivity, and linearity were documented. For both methods, samples in ultrapure water and NaHCO₃ have an R² value>0.99, indicating strong linear relationships. Statistical analysis supports that NaHCO₃ does not affect linearity between standards for either method. NaNO₃ causes major interference with the ketoxime method above 0.001 M NaNO₃. Data provides information for practical use of Re spectrophotometric methods in environmental media that is high in bicarbonate and nitrate.