The effect of different matrices on the SERS sensor performance was studied by spiking both commercial mineral water and river water samples with known 2,4-D concentrations. The mineral composition for the commercial mineral water is shown in table in SI. Ten measurements were undertaken for each concentration on a substrate, the experiments were repeated three times on three individual SERS substrates. The error bar was calculated using data from the standard deviation (SD) of the three replicates across the three SERS substrates and show that the interaction of the sensor with 2,4-D in the presence of different ions remains largely unaffected.