Abstract
This paper investigated the feasibility of Fourier transform infrared transmission (FT-IR) spectroscopy to detect talcum powder illegally added in tea based on chemometric methods. Firstly, 210 samples of tea powder with 13 dose levels of talcum powder were prepared for FT-IR spectra acquirement. In order to highlight the slight variations in FT-IR spectra, smoothing, normalize and standard normal variate (SNV) were employed to preprocess the raw spectra. Among them, SNV preprocessing had the best performance with high correlation of prediction (RP = 0.948) and low root mean square error of prediction (RMSEP = 0.108) of partial least squares (PLS) model. Then 18 characteristic wavenumbers were selected based on a hybrid of backward interval partial least squares (biPLS) regression, competitive adaptive reweighted sampling (CARS) algorithm and successive projections algorithm (SPA). These characteristic wavenumbers only accounted for 0.64% of the full wavenumbers. Following that, 18 characteristic wavenumbers were used to build linear and nonlinear determination models by PLS regression and extreme learning machine (ELM), respectively. The optimal model with RP = 0.963 and RMSEP = 0.137 was achieved by ELM algorithm. These results demonstrated that FT-IR spectroscopy with chemometrics could be used successfully to detect talcum powder in tea.
Highlights
This paper investigated the feasibility of Fourier transform infrared transmission (FT-IR) spectroscopy to detect talcum powder illegally added in tea based on chemometric methods
The average spectra of pure tea sample, tea sample with 1.50 mg/g talcum powder and pure talcum powder are demonstrated in Fig. 1(a–c), respectively
For the pure talcum powder spectrum, the main absorbance peaks were observed in the range of 990–1055 cm−1 (see enlarged peaks in Fig. 1(d)), which can be attributed to the Si-O-Si group[23]
Summary
This paper investigated the feasibility of Fourier transform infrared transmission (FT-IR) spectroscopy to detect talcum powder illegally added in tea based on chemometric methods. The optimal model with RP = 0.963 and RMSEP = 0.137 was achieved by ELM algorithm These results demonstrated that FT-IR spectroscopy with chemometrics could be used successfully to detect talcum powder in tea. Chen et al.[7] and Xiang et al.[8] investigated talcum powder in tea based on traditional chemical methods. In these researches, the existence of talcum powder in tea was arbitrarily inferred based on the existence of magnesium[7,8]. Chemometric methods play a important role in wavenumbers www.nature.com/scientificreports/
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