Dear Shankar Moorthy

Accurate wavelength of specific product doesn't exist in NIR region ! Peak identification is a a valuable method in MIR region. In NIR you shoud rather consider all spectra or a wide range of the spectra and apply multivariate statistics to recognize or quantify your product

Best regards

Damien

For analysis and prediction of glucose, the wavelength between 1500–1850 nm in the first overtone region and 2050–2392 nm in the combination over-tone band are more suitable, as absorption by water is low and measuring signal has high energy in these regions. higher overtone 800-1100 nm is considered for reflectance based measurement