A Novel Silica Gel Adsorption/Near-Infrared Spectroscopic Method for the Determination of Hexanal as an Example of Volatile Compounds

The present research has demonstrated the feasibility of using silica gel adsorption/near-infrared (near-IR) reflectance spectroscopy to determine hexanal as an example of volatile compounds. Using a first-derivative mathematical treatment for the near-IR spectra of hexanal adsorbed on silica gel provides better results than the raw near-IR spectra. The wavelengths from 1650 to 1790 nm show a linear relationship between first-derivative near-IR reflectance and hexanal contents on silica gel. The two best simple linear regression equations [Y L = 7.89 x 10 -6 + 1.711 x 10 -4 (X L ); Y H = 4.319 x 10 -4 + 8.69 x 10 -5 (X H )] obtained from the regression equations of eight groups fit in lower hexanal contents ranging from 7.8 to 39 mg/10 g of Si and higher hexanal contents ranging from 39 to 546 mg/10 g of Si, respectively. The correlation coefficient between the near-IR-predicted value using the two equations and the added standard value of hexanal adsorbed on silica gel is 0.997. The relative errors were less than 9%.