2.6.1. Sensitivity

In this study, the spiked milk and pork samples with a series of DEX concentrations were used to assess the sensitivity of the developed TRFM-ICG; each spiked concentration was detected in triplicate. The sensitivity was expressed by the cut-off value, calibration curve, and limit of quantitation (LOQ). The cut-off value was defined as the lowest DEX concentration that can cause the T-line signal to disappear. The fluorescence intensity of the T/C line can be achieved by the fluorescence reader. The DEX concentration in milk or pork sample was quantified by the calibration curve, taking the concentration of DEX as the x-axis and B/B0 (T/C line fluorescence signal ratio, where B is with analyte in the reaction system and B0 is without analyte in the reaction system) as the y-axis. The LOQ was defined as the concentration corresponding to 80% of B/B0 value on the calibration curve [29].
