Micro-analysis by near-infrared diffuse reflectance spectroscopy with chemometric methods

Great attention has been paid to near-infrared diffuse reflectance spectroscopy (NIRDRS) due to its practicability in analyzing real complex samples. However, the application of the technique in micro-analysis is badly restricted by its low sensitivity or high detection limit. In this study, the possibility of achieving the sensitive detection of micro-components using NIRDRS with the help of chemometric methods is studied with two experimental datasets. The results show that a very high sensitivity can be obtained when the noise and the variant background are minimized. Quantitative determination of low concentrations of pesticides and trace Cr3+ in solutions is achieved by using preconcentration and chemometric approaches to minimize the noise and background. The absolute prediction error of the method can be as low as 7.6 μg for the pesticide and 28.6 μg for Cr3+. These quantities are equivalent to 76 ng mL−1 and 286 ng mL−1 if 100 mL of solution are used for the analysis.