Next, we generated a calibration curve and determined the limit of detection (LOD). Analyte solutions were Na2HPO4 and glucose solution. Phosphate is a major component in the popular buffer, phosphate-buffered saline (PBS), which has wide used in biological studies. Glucose exists in different biofluids in our bodies at a wide range of concentrations. The spectra to calculate the integration value were acquired with 2 co-additions and an 8 cm -1 spectral resolution.