Then the concentration of STG CSTG could be

The concentration of the mixture that represented (12CSTG+CMET) could be calculated by using a regression equation representing the linear relationship between the absorbance of MET at the absorptivity factor point λF (208 nm) and its corresponding concentration. The concentration of MET (CMET) in the mixtures could be determined separately by using its regression equation representing the linear relationship between the absorbance of MET at 232 and its corresponding concentration.