These two chemicals both have broad application in studying biological assays. Na2HPO4 is the major constituent of phosphate-buffered saline (PBS), a common buffer solution for studying microbial sample in microfluidics 17 D-glucose is also a common composition in many nutrient solutions as the energy source for cultivating microbes. The deionized water which was the solvent for sample solution was used as the background sample here. Both the water and solution were loaded onto the open channels by dropping from a pipette. After the background was acquired, the deionized water was removed from the surface first by a swapping cotton. Then, the open channel was rinsed and cleaned with following analyte 3 times before next measurement.