What is the wavelength of the adsorption spectrum of As elements in the visible region in the pH 4 buffer in the UV spectrum? I would appreciate it if anyone has knowledge. Thank you.
Most of the elements you mentioned, absorb as cations mainly in the UV range. THe absorption of pure Pb2+, e.g. in water can be found in AIP Conference Proceedings 2145, 020008 (2019); https://doi.org/10.1063/1.5123569
Just Cu2+ shows a high absorption cross section in the visible (and IR) range, which is strongly governed by the pH value. The following open access paper might help you!
All the best for your research,
Thomas
Journal of The Electrochemical Society Determination of Stability Constants of Copper(II)–Lactate Complexes in Cu2O Electrodeposition Baths by UV-vis Absorption Spectra Factor Analysis Tianyu Chen et al 2019 J. Electrochem. Soc. 166 D761