Antaris 2

In this study, a Fourier Transform near-infrared spectrometer (Antaris II, Thermo Fisher Scientific, US) was used for spectral information collection. Before collecting spectral data, the spectrometer was preheated for half an hour to ensure a stable scanning state. Then, using the integrating sphere diffuse reflectance sampling module, approximately 3 g of tea powder was loaded into a sample cup rotator with an inner diameter of 4.78 cm. The sample cup was shaken to cover the bottom detection surface with tea powder before the sample was ready for testing. The instrument parameters were set to 64 scans, with a gain of 2 in the room temperature of approximately 25 °C. The background spectrum was removed and air was used as a reference. For each tea powder sample, near-infrared spectra were scanned at three different positions 120° apart at the bottom of the powder. The average of these three sets of spectral data was taken for analysis. After collecting the sample spectra, the tea powder was used for chemical content detection. Meanwhile, the sample cup was cleaned and prepared for the next collection.

SPI samples were scanned using a Fourier-transform near-infrared spectra analyzer (Antaris II, Thermo Fisher, Waltham, MA, USA). Samples were gently pressed into the dish (30 mm), then tapped three times with a spatula to ensure even packing. NIR spectra were captured at wavelengths of 10,000–4000 cm⁻¹ (64 scans) measured as absorbance at a resolution of 8 cm⁻¹ [14 (link)].

W. cocos samples’ spectra were collected by FT-NIR spectrometer (Thermo Scientific Inc., Antaris II). This instrument needed to be warmed up for 2 hours before collecting samples’ spectra to ensure its stability and accuracy. A sufficient amount of sample powder was placed in the sample cup. Under the condition of the spectral resolution of 8 cm^-1 with a scanning range of 10000-4000 cm^-1, the scanning times of each sample were 64, and the samples were collected twice in parallel. In this study, the average spectrum of the sample was used as the data source for subsequent NIR spectrum modeling. It is worth mentioning that the background signal needs to be collected every hour for correction to eliminate the interference of air. In addition, when collecting spectral information, it is necessary to make the air humidity and temperature stay at 45°C and at 25%, respectively.

An Antaris II spectrometer (Thermo Fisher Scientific, USA) with integrating sphere diffused reflection mode was used for obtaining NIR spectra of sample powders. Spectrum scan range was 10 000–4000 cm⁻¹. Resolution was 8 cm⁻¹ and each sample power has 64 accumulated scans. The obtained spectra were recorded as the logarithm of reciprocal reflectance, log(1/reflectance). In order to reduce the operation error, 20.0 g powder was filled up a uniform glass vessel to scan one by one. In addition, humidity and room temperature were kept at 30% and 25°C, respectively, in the course spectra collection to exclude interference of laboratory air. Finally, the average spectrum from triplicate measurement was calculated as the final spectrum for mathematical analysis.

The Fourier-transform near-infrared spectra (FT-NIR) were measured using the Antaris II FT-NIR analyzer (Thermo Scientific, Waltham, MA, USA). The instrument was equipped with an integrating sphere enabling diffuse reflection analysis of different materials, including powdered samples. The FT-NIR absorbance spectra were collected between 10,000 cm⁻¹ and 4000 cm⁻¹ with 2 cm⁻¹ resolution, i.e., between 1000 nm and 2500 nm, directly through glass vials. Before collecting the spectra of adulterated ground garlic mixtures, moisture was removed from the samples through drying them to constant weight in a laboratory dryer at 80 °C. Then, they were carefully mixed to obtain an even distribution of an adulterant in a sample. Finally, each mixture was described using the average FT-NIR spectrum of 32 independent scans. Spectroscopic measurements were carried out at stable room temperature (22 °C) and humidity (50%). Spectra were recorded thirty minutes after switching on the instrument in order to stabilize the radiation source. The background spectrum was recorded at the beginning of the measurements. The background correction procedure was repeated automatically every hour using an internal standard (diffusely reflective gold plate).