The absorption of light in the medium is described by the equation A = ɛdc, where A is the amount of light of a certain wavelength that was absorbed by the sample, ɛ ( l/mol cm) is the molar absorption coefficient (extinction), d is the distance traveled by the light in the solution,cuvette length (сm) and c (mol / liter) is the concentration of the solution (the number of molecules studied in a unit volume). The absorption coefficient can also be found using a spectrophotometer from the ratio between the intensities of the light transmitted through the standard Io and the sample under study. In this case, the equation has the following form: A = log (Io / I), dimensionless quantity. Absorbency of the solution depends on the wavelength of light passing through it. At certain wavelengths, light is absorbed more strongly than with others, and these values depend on the composition of the solution. When making calculations, do not forget to indicate for what wavelength they are made.

Thank you Dr. Mirgorod for your suggestions. However, I have MoS2 dispersed in N-methyl-pyrollidonne. Being a high boiling point organic solvent, it's really hard to know the concentration of MoS2. I tried to measure the concentration gravimetrically but NMP polymerizes during the process.

You can determine the amount of "Mo" by ICP-MS or ICP-OES. Then you can do calculations for MoS2.

Thank you Dr. Khan. But isn't ICP MS applicable for ions? Will it work for MoS2?