ab·sorp·ti·om·e·try 
(əb-zôrp′tē-ŏmĭ-trē, -sôrp′-)
(əb-zôrp′tē-ŏmĭ-trē, -sôrp′-)n.
A method of chemical analysis in which a sample of a substance is exposed to electromagnetic radiation, and the amount of radiation absorbed is measured to determine the chemical composition or concentration of the substance.