How do we decide wavelength for taking O.D of a compound using spectrophotometer? Is it the color or some thing else which is taken into consideration while deciding the wavelength? Kindly reply if any body knows.

hi there
in colour detection and absorbption system if u dont know the wavelength of a particular compound then u have to for a wavelength scan in that where u r absrtn is maximum that is ur wavelength of a particular compound.it follows by graph ok

Always the wavelength that gives the maximum absorption of a compound is considered.A compound either in U.V. or Visible spectroscopy is scanned between 200nm-1000nm.The peak at the maximum absorption is considered.This wavelength is considered for all the solutions.

Here are some pretty decent links for UV-Vis Spectroscopy theory...


Penn State Material Characterization Laboratory - UV-Vis Basic Theory


Univeristy of Missouri-Columbia: UV-VIS Absorption Spectroscopy


Virginia Tech, Dept of Chemistry - Ultraviolet and Visible Absorption Spectroscopy (UV-Vis)


International Union of Pure and Applied Chemistry - MOLECULAR ABSORPTION SPECTROSCOPY, ULTRAVIOLET AND VISIBLE (UV/VIS)


Sheffield Hallam University - UV-Vis Absorbtion Spectroscopy


Sheffield Hallam University - UV-Vis Luminescence Spectroscopy



To answer the question, you will want to scan your sample over the wavelength of the UV-Vis spectrum (i.e. 400 - 800 nm)