**Table 2.** *Cont.*


#### *3.4. Water Sample Analysis by ELISA and UPLC–MS/MS*

The N56-based ic-ELISA was further employed to analyze water samples spiked with NOD-R at three concentrations (0.5, 1, 2 μg/L). As shown in Table 3, the average recovery ranged from 111.0% to 119.5%, with CVs of 2.0–5.8%. The value of the correlation coefficient (R2) between ic-ELISA and UPLC–MS/MS was up to 0.999, indicating that the established N56-based ic-ELISA is accurate and reliable for detecting NOD-R in water samples.


