This was followed by a gaussian smoothing with standard deviation as 4. For glucose, the peak centered at 1100 cm -1 was integrated from 930 to 1180 cm -1 , which is assigned as the C-O-C stretching of glucose backbone For Na2HPO4, the peak centered at 990 cm -1 was integrated from 964 to 1003 cm -1 , which was assigned as P-O asymmetric stretching The integral data were then transfer to Microsoft Excel for linear regression and plotting.