Rapid determination of vitamin C by NIR, MIR and FT-Raman techniques.

Rapid spectroscopic determination of vitamin C in food and pharmaceutical products using infrared and Raman techniques was proposed. In this study, near-infrared (NIR), Fourier transform near-infrared (FT-NIR), Fourier transform infrared-attenuated total reflectance (FTIR-ATR), diffuse reflectance (DRIFTS), Fourier transform infrared-photoacoustic (FTIR-PAS) and FT-Raman spectroscopy were used in conjunction with partial least squares (PLS) regression to quantify vitamin C in powdered mixtures and solutions. Results indicate that the methods adopted have high prediction correlation. R2 values were 0.999 for FTIR-ATR, 0.976 for DRIFTS, 0.966 for FTIR-PAS, 0.988 for NIR, 0.992 for FT-NIR and 0.95 for FT-Raman, with an overall prediction error of 0.2-3.0%. The time required to complete an experiment ranged from 5 s (NIR) to 3 min (FT-Raman). The FTIR and FT-Raman techniques can be complementary tools for qualitative and quantitative characterization of the samples. Infrared and Raman techniques can be used to quantify vitamin C in foods and pharmaceutical products.