Malathion pesticide gives maximum absorbance at 760nm

Rozita Foulady Generally pesticides are colourless and would not have maximum absorption in the visible range (400 to 800 nm)

You can convert them using azo derivatization for colorimetric determination. see

Zweig, Gunter, and Joseph Sherma, eds. Spectroscopic Methods of Analysis: Analytical Methods for Pesticides and Plant Growth Regulators, Vol. 9. Vol. 9. Elsevier, 2013.

The Linuron and Fenarimol were detected at 210 and 250nm.

We can read my two papers. see blow:

- Belaroui, L.S., Ouali, A., Bengueddach, A., Lopez Galindo, A., Pena, A. (2018) :Adsorption of linuron by an Algerian palygorskite modified with magnetic Iron.. Applied Clay Science, 164, 26-33, DOI:10.1016/j.clay.2018.03.021

- Ouali, A., Belaroui, L.S., Bengueddach, A., Lopez Galindo, A., Pena, A. (2015). Fe2O3-palygorskite nanoparticles, efficient adsorbates for pesticide removal. Applied Clay Science, 115, 67-75. DOI:10.1016/j.clay.2015.07.026

Lala Setti Belaroui These two compounds ( Linuron and Fenarimol ) are detected in the UV region, not visible (>350 or 400-800 nm).

Hi, Rozita,

Very often, the nature of the solvent and even the pH of the solution influences the absorbance wavelength value of a pesticide. This value can shift towards a wavelength in the visible domain

M.Y.Shukor Yes, I Know. The values of wavelength were mentioned in the first comment.