Rapid discrimination of sulfur-fumigated lily by mid-infrared, near-infrared and synchronous fluorescence spectroscopy and chemometrics: a comparative study.

Lily, as a traditional Chinese medicinal herb, is often fumigated with sulfur due to its high starch content, which makes it difficult to dry and prone to mold during storage and transportation. Sulfur-fumigated lily will produce new compounds that pose a threat to medication safety. This work implements a comparative study on identification of sulfur-fumigated lily by Fourier-transform mid-infrared (FTIR), near-infrared (NIR) and synchronous fluorescence (SF) spectroscopy combined with chemometrics. Principal component analysis (PCA) and soft independent modeling of class analogy (SIMCA) are used as the exploratory and class-modeling tools, respectively. A set of simulated samples is prepared in the laboratory, considering the effects of different concentration levels and sulfur-fumigation time. The focus is on identifying the samples sulfur-fumigated at the lowest concentration. NIR spectroscopy achieves the best performance, with 100 % recognition accuracy; MIR spectroscopy achieves an accuracy of 97.9 %, while SF spectroscopy achieves 100 % accuracy when the excitation and emission wavelength intervals are between 20 and 160 nm. These three spectroscopic techniques have the potential of developing green and low-cost methods for identifying whether lily is sulfur-fumigated or not.