A method of determining a concentration of analytes of interest in a sample reaction mixture is disclosed. The method can include measuring intensities of the polarized fluorescence of at least one comparative reaction mixture containing different, known amounts of the analytes of interest, and measuring the intensities of the polarized fluorescence of a sample reaction mixture. The method can also include determining the preliminary concentrations of the analytes of interest in the sample reaction mixture by comparing the measured intensities of the sample reaction mixtures at various time points. The margin of error for the preliminary concentration of the analytes of interest in the sample can be determined at the various time points. Finally, the concentration of the analytes of interest in the sample reaction mixture can be determined by comparing the preliminary concentrations and the respective margin of error at the given time points.