Spectrophotometer nrog lub teeb muaj peev xwm tsim tau ntau lub yoj ntawm lub teeb pom kev, dhau los ntawm cov khoom siv hluav taws xob ntau, ua rau muaj qhov tshwj xeeb ntawm lub teeb ntawm lub teeb, cov teeb ci los ntawm cov qauv ntsuas, ib feem ntawm lub teeb tau nqus, xam cov nqi piv txwv, uas yog hloov mus rau hauv cov concentration ntawm cov qauv. Cov hnoos qeev ntawm kev nqus tau tus nqi sib npaug sib xyaw ua ke rau cov concentration ntawm cov qauv.
Monochromatic lub teeb hluav taws xob dhau los ntawm cov khoom siv hauv qhov kev ntsuas cov tshuaj, qhov ntau ntawm qhov nqus los ntawm cov khoom thiab qhov kub siab ntawm cov khoom thiab cov tuab ntawm cov kua txheej tau sib npaug rau cov kab nrig kho qhov muag ntev, kev sib raug zoo yog li hauv qab no:
A=- lg (Kuv / Kuv).=- lgT=kLc
Hom: A, rau kev nqus.
I. Rau kev siv lub teeb;
Kuv rau kev kis ntawm lub teeb sib kis;
T rau kev sib kis cov ntaub ntawv;
K raws li cov hniav sib nqus nqus coefficient;
L yog txheeb xyuas lub cev txoj kev kho qhov muag, uas yog, sab ntev ntev ntawm colorimetric zaub mov;
C yog kev cia siab ntawm cov tshuaj yeeb dej caw;
Cov khoom siv xaiv nqus wavelength ntawm lub teeb, thiab qhov sib txuam nqus coefficient yog cov khoom siv tsis tu ncua. Thaum cov tshuaj ntshiab paub nyob hauv qee yam kev mob muaj nyob tom qab kev nqus coefficient ntawm cov qauv ntsuas hauv tib qho kev daws teeb meem, ntsuas nws qhov kev nqus, tuaj yeem muab xam los ntawm hom kev ntsuas qhov ntsuas hauv cov ntsiab lus ntawm cov khoom. Kev nqus lub teeb nyob hauv thaj chaw pom pom, ntxiv rau qee yam khoom, ntau cov khoom nws tus kheej tsis nqus tab sis tuaj yeem koom nrog chromogenic reagent hauv qee yam kev mob lossis tom qab ua tiav nws cov xim ntsuas dua, yog li nws tseem hu ua xim tsom xam. Raws li cov keeb kwm chromogenic cuam tshuam rau xim qhov tob yog ntau dua, thaum cov neeg pluag thiab feem ntau siv monochromatic lub teeb purity ntawm ntsuas, yog li kev txiav txim siab ntawm daim ntawv thov ntawm cov qauv txheem thiab cov khoom siv cuam tshuam rau tib lub sijhawm.
