The calibration curve suggests, for this experiment setup, the limit of detection (LOD) for glucose is approximately at 3 mM. This is an improved result comparing to the previous study using a similar setup, in which the LOD was approximately at 27 mM. We attribute the improvement to the ridge orientation that was perpendicular to the optical axis and the enlarged surface area that was in contact with the liquid. We note that the band area stopped decreasing at this concentration indicating that the limit of detection was being driving by an adsorbed D-glucose layer at the surface, rather than a limit of detection in the bulk liquid. The limit of detection for Na2HPO4 was only 1 mM and did not appear to be limited by an adsorbate, as the HPO3 ions is smaller and does not participate in non-specific adsorption such as large organic molecules like