Rapid identification method for stoving traditional Chinese medicinal materials and measuring method for SO2 residual quantity of stoving traditional Chinese medicinal materials

Abstract

The invention discloses a rapid identification method for stoving traditional Chinese medicinal materials and a method for measuring SO2 residual quantity. The method comprises the following steps: firstly, obtaining a terahertz absorption spectrum of a traditional Chinese medicinal material sample to be detected; then, observing whether the terahertz absorption spectrum has a characteristic peak at 1.41 THz, and if so, judging that the traditional Chinese medicinal material is the stoving traditional Chinese medicinal material; when the residual quantity of SO2 is measured, the characteristic peak intensity at the 1.84 THz position of the terahertz absorption spectrum is firstly measured, and the residual quantity of SO2 in the traditional Chinese medicinal material to be measured is calculated according to a pre-established standard curve between the 1.84 THz characteristic peak intensity and the residual quantity of SO2. According to the method, complex sample pretreatment is not needed, the detection process is simple, convenient and rapid, whether the traditional Chinese medicinal materials are subjected to stoving or not can be rapidly judged, when the residual amount of SO2 is quantitatively measured, single-time measurement only needs several minutes, and the method is remarkably superior to a traditional physical and chemical method with the detection period as long as several hours. And the method can be used for measuring various traditional Chinese medicinal materials such as gastrodia elata, codonopsis pilosula, Chinese yam and the like, and is high in universality.

Description

Technical Field

[0001] This invention belongs to the field of analytical testing technology, specifically relating to a rapid identification method for sulfur-fumigated Chinese medicinal materials and a method for measuring SO2 residue. Background Technology

[0002] Sulfur fumigation (hereinafter referred to as "sulfur fumigation") is a common method in the processing of Chinese medicinal materials at their place of origin. It is widely used in the treatment of various medicinal materials such as ginseng, angelica, yam, angelica sinensis, codonopsis, and chrysanthemum to achieve the purposes of preservation, insect prevention, bleaching, and easy drying. However, excessive or illegal sulfur fumigation can lead to changes in the properties and flavor of Chinese medicinal materials, loss of effective components, and excessive sulfur dioxide (SO2) residues, posing a potential threat to human health.

[0003] To control the quality of Chinese medicinal materials, the Chinese Pharmacopoeia (2025 edition) has set limits for SO2 residues (usually not exceeding 150 mg / kg) for 11 kinds of medicinal materials and processed slices, including yam and gastrodia elata, and uses acid-base titration, gas chromatography, and ion chromatography as standard detection methods. All these methods require first removing residual SO3 from sulfur-fumigated medicinal materials. 2- It is converted into SO2 and separated from the substrate, and then converted into SO3. 2- The measurement is performed and finally converted into SO2 residue. Although the accuracy is high, it generally suffers from problems such as complex sample pretreatment, cumbersome operation and long time consumption, which makes it difficult to meet the needs of rapid on-site detection.

[0004] In the prior art, patent application CN112113950A proposes a rapid detection method based on surface-enhanced Raman spectroscopy. However, this method relies on a specially prepared Si@Ag@PEI composite substrate, which is complex to operate and difficult to achieve rapid detection. Moreover, surface-enhanced Raman spectroscopy technology has a high threshold and high cost, which is not conducive to its widespread adoption. Another patent application CN118243656A uses terahertz time-domain spectroscopy combined with machine learning to classify Angelica dahurica with different degrees of sulfur fumigation. However, this method relies on complex modeling and does not establish a direct quantitative relationship between SO2 residue and spectral characteristics, lacking quantitative judgment basis. In addition, this method requires a high level of knowledge in chemometrics from the operator, has weak applicability, and is difficult to promote. Furthermore, it is limited to Angelica dahurica alone, and its universality is also weak.

[0005] Therefore, there is still a lack of existing technologies for a qualitative and quantitative detection method of SO2 residues that is fast, simple, accurate, and applicable to a variety of sulfur-fumigated Chinese medicinal materials. Summary of the Invention

[0006] In view of the above-mentioned shortcomings of the existing technology, the purpose of this invention is to provide a rapid identification method for sulfur-fumigated Chinese medicinal materials and a method for measuring SO2 residues in them, so as to solve the problems that the existing measurement techniques are cumbersome to operate, have poor universality, and are difficult to quickly identify sulfur-fumigated Chinese medicinal materials and determine the SO2 residues in them.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0008] A rapid identification method for sulfur-fumigated Chinese medicinal materials includes the following steps:

[0009] a) Prepare samples of the Chinese medicinal materials to be tested and obtain their terahertz absorption spectra;

[0010] b) Observe whether there is a characteristic peak at 1.41 THz in the terahertz absorption spectrum. If there is, the Chinese medicinal material is determined to be sulfur-fumigated. If there is no characteristic peak, the Chinese medicinal material is determined to be unfumigated.

[0011] Furthermore, the preparation of the Chinese medicinal material sample to be tested in step a) includes slicing, drying, pulverizing, sieving and pressing the Chinese medicinal material into tablets.

[0012] Furthermore, the medicinal materials mentioned include Gastrodia elata, Codonopsis pilosula, or Dioscorea opposita.

[0013] A method for measuring SO2 residue in sulfur-fumigated Chinese medicinal materials includes the following steps:

[0014] a) Prepare samples of the Chinese medicinal materials to be tested and obtain their terahertz absorption spectra;

[0015] b) Measure the intensity of the characteristic peak of the terahertz absorption spectrum at 1.84 THz;

[0016] c) Calculate the SO2 residue of the Chinese medicinal material to be tested based on the pre-established standard curve between the intensity of the characteristic peak at 1.84 THz and the SO2 residue.

[0017] Furthermore, the preparation of the Chinese medicinal material sample to be tested in step a) includes slicing, drying, pulverizing, sieving and pressing the Chinese medicinal material into tablets.

[0018] Furthermore, the sieving is performed through a 200-mesh sieve.

[0019] Furthermore, the standard curve is established in the following manner:

[0020] i. Prepare a series of standard samples of Chinese medicinal materials with different sulfur fumigation levels and known SO2 residues;

[0021] ii. Obtain the terahertz absorption spectrum of each standard sample and measure its characteristic peak intensity at 1.84 THz;

[0022] iii. Using the intensity of the characteristic peak as the abscissa and the SO2 residue of the corresponding standard sample as the ordinate, perform linear fitting to obtain a standard curve.

[0023] Furthermore, the residual SO2 content in the standard sample was determined by acid-base titration.

[0024] Furthermore, the standard curve is y = 2653.6x - 92.671, where y is the residual SO2 content and x is the characteristic peak area at 1.84 THz.

[0025] Furthermore, the medicinal materials mentioned include Gastrodia elata, Codonopsis pilosula, or Dioscorea opposita.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. This invention provides a rapid identification method for sulfur-fumigated Chinese medicinal materials and a method for measuring SO2 residues in sulfur-fumigated Chinese medicinal materials. This method systematically analyzes the terahertz spectral characteristics of Gastrodia elata and various sulfur-containing compounds before and after sulfur fumigation. For the first time, it clearly identifies the 1.41 THz characteristic peak as the qualitative basis for sulfur fumigation determination. By identifying the presence of the characteristic peak at 1.41 THz, the identification of sulfur-fumigated Chinese medicinal materials can be achieved rapidly. Further research revealed that the characteristic peak at 1.84 THz is unique to sulfite ions (SO32-), and its intensity shows a stable positive correlation with sulfur fumigation time and SO2 residue, thus establishing it as a key indicator for quantitative analysis. Based on this, by constructing a standard curve between the intensity of the 1.84 THz characteristic peak and SO2 residue, rapid and accurate quantification of SO2 residues in various sulfur-fumigated Chinese medicinal materials is achieved.

[0028] 2. The method of this invention requires no complex sample pretreatment, is simple to operate, and can be completed in a few minutes, greatly improving detection efficiency and significantly outperforming the detection cycle of traditional physicochemical methods, which can take several hours. Furthermore, experimental verification has shown that this method exhibits good accuracy and applicability in various Chinese medicinal herbs such as Gastrodia elata, Codonopsis pilosula, and Dioscorea opposita, providing a reliable and efficient technical means for rapid on-site screening and quality supervision of sulfur dioxide residues in Chinese medicinal herbs. Attached Figure Description

[0029] Figure 1 A comparison of the terahertz absorption spectra of Gastrodia elata before and after sulfur fumigation;

[0030] Figure 2 The terahertz absorption spectra of S8 and Na2SO3 are shown.

[0031] Figure 3 The terahertz absorption spectra of S8 and Na2SO4 are shown.

[0032] Figure 4 Terahertz absorption spectra of Gastrodia elata fumigated with sulfur for different times;

[0033] Figure 5 This is a comparison of the peak areas of Gastrodia elata at the characteristic peak of 1.84 THz under different sulfur fumigation times.

[0034] Figure 6 The linear relationship between the characteristic peak area at 1.84 THz and the corresponding SO2 residue measured by acid-base titration for Gastrodia elata samples with different sulfur fumigation levels is shown in the figure.

[0035] Figure 7 The images show the terahertz absorption spectra of the prepared sulfur-fumigated Gastrodia elata and the unfumigated Gastrodia elata in Example 1.

[0036] Figure 8 The image shows the terahertz absorption spectrum of commercially available Gastrodia elata from Example 2.

[0037] Figure 9 The image shows the terahertz absorption spectrum of the Codonopsis pilosula sample in Example 3.

[0038] Figure 10 The image shows the terahertz absorption spectrum of the yam sample in Example 4. Detailed Implementation

[0039] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments, but the scope of protection of the present invention is not limited to the embodiments described.

[0040] This invention addresses the problems of existing methods for detecting SO2 residues in sulfur-fumigated Chinese medicinal materials, which are cumbersome, time-consuming, have poor applicability, or rely on complex modeling. It provides a method based on terahertz spectroscopy for rapid identification and quantitative detection of SO2 residues in sulfur-fumigated Chinese medicinal materials. The inventive concept is as follows: First, by comparing the terahertz absorption spectra of the Chinese medicinal materials and their related sulfides (sulfur S8, sodium sulfite, sodium sulfate) before and after sulfur fumigation, the characteristic absorption peak of sulfur (S8) at 1.41 THz was discovered and confirmed as a qualitative criterion for sulfur fumigation. Simultaneously, sulfite ions (SO32-) were screened out. 2- The method identifies a unique characteristic peak at 1.84 THz. Furthermore, by establishing a quantitative relationship between the intensity of this characteristic peak at 1.84 THz and the SO2 residue measured by acid-base titration for samples with different degrees of sulfur fumigation, a quantitative analysis standard curve is constructed. This method ingeniously utilizes terahertz spectroscopy to directly and rapidly capture the distinguishing characteristics of specific sulfides in samples, thereby achieving rapid identification without complex pretreatment or modeling, and enabling simultaneous qualitative and quantitative analysis. This provides a powerful technical means for the quality control of various sulfur-fumigated Chinese medicinal materials.

[0041] The specific research process of this invention is as follows:

[0042] 1. Experimental Materials and Instruments

[0043] 1.1 Experimental Materials

[0044] Samples of Chinese medicinal materials: freshly picked or purchased from the place of origin, including Gastrodia elata, Codonopsis pilosula, and Dioscorea opposita.

[0045] Sulfur fumigation reagent: analytical grade sulfur (S8).

[0046] Reference reagents: analytical grade sodium sulfite (Na2SO3), analytical grade sodium sulfate (Na2SO4), and analytical grade sulfur (S8).

[0047] 1.2 Main Instruments and Equipment

[0048] Terahertz time-domain spectroscopy system: TQ-1000 (Qingdao Qingyuan Fengda Terahertz Technology Co., Ltd.). Under experimental conditions, the effective terahertz band is 0.1-2.5 THz.

[0049] Sample pretreatment equipment:

[0050] Vacuum drying oven: used for low-temperature drying of samples.

[0051] Chinese medicine pulverizer: used for pulverizing dried samples.

[0052] Standard sieve for sample division: 200 mesh (approximately 75 μm pore size).

[0053] Tableting machine: pressure range 0-40MPa, with a matching mold with a diameter of 13mm.

[0054] Agate mortar: used for fine grinding of powder samples.

[0055] 2. Sample preparation method

[0056] 2.1 Preparation of sulfur-fumigated samples

[0057] (1) Take 100g of fresh, whole Chinese medicinal materials (taking Gastrodia elata as an example) and divide the materials into two equal portions of 50g each. One portion is used as a control sample without sulfur fumigation, and the other portion is used as a sample treated with sulfur fumigation.

[0058] (2) The sulfur-fumigated samples were subjected to sulfur fumigation in a sealed glass tank within a fume hood. Specifically, 50g of the gastrodia elata to be fumigated was evenly placed on a perforated plastic support inside the tank. A heat-resistant ceramic crucible was then placed at the bottom of the glass tank, and 5g of sulfur powder was weighed into it and ignited with a lighter. Afterward, the tank lid was quickly closed for sulfur fumigation for 2 hours. After fumigation, the tank lid was opened, and the sample was removed to obtain the sulfur-fumigated sample.

[0059] (3) To prepare samples with different sulfur fumigation levels, the sulfur fumigation time can be set to 2h, 4h, 6h and 8h respectively, and the rest of the operation is the same as above.

[0060] 2.2 Preparation of Terahertz Test Samples

[0061] (1) Slicing and drying: The gastrodia elata samples after sulfur fumigation (2h, 4h, 6h, 8h) were sliced ​​into thin slices with a thickness of about 1cm using a stainless steel knife. The slices were evenly spread in a tray and placed in a vacuum drying oven at 60℃ for 4h to remove most of the moisture and avoid the decomposition of components caused by high temperature.

[0062] (2) Crushing and sieving: The dried sample slices were initially crushed using a Chinese medicine crusher and then passed through a 200-mesh standard sieve to obtain the powder to be tested for each sample.

[0063] (3) Tableting: Accurately weigh 0.2g of a certain test powder using an analytical balance, pour it into a clean agate mortar and grind it thoroughly to disperse it evenly. Then transfer all the powder to a tableting mold with a diameter of 13mm, and use a tablet press to press it into a circular sheet with a thickness of about 1mm and a uniform and flat surface, thus obtaining the terahertz test sample of the test powder. Weigh other test powders in sequence and repeat this step to obtain the terahertz test sample of each sample.

[0064] 3. Terahertz spectroscopy measurement

[0065] Each terahertz test sample was placed sequentially at the detection window of the terahertz time-domain spectroscopy system. Under constant temperature (25±1℃) and constant humidity (relative humidity <5%) conditions, the terahertz time-domain spectrum of each terahertz test sample was tested. The time-domain signal was converted into a frequency-domain signal by fast Fourier transform, and the absorption spectrum of the sample in the range of 0.1-2.5THz was calculated.

[0066] 4. Establishment of Qualitative Identification Methods

[0067] 4.1 Identification of characteristic peaks from sulfur fumigation

[0068] like Figure 1 As shown, comparing the absorption spectra of un-sulfurized Gastrodia elata and Gastrodia elata fumigated for 2 hours with sulfur, a new and significant characteristic absorption peak appeared at 1.41 THz in the sulfur-fumigated Gastrodia elata, which was not present in the un-sulfurized sample. This indicates that the 1.41 THz peak is directly related to the sulfur fumigation process.

[0069] 4.2 Confirmation of the attribution of characteristic peaks

[0070] To confirm the source of the 1.41 THz peak, pure sulfur (S8), Na2SO3, and Na2SO4 were compressed into tablets (method as in 2.2-(3)) and their terahertz absorption spectra were measured. The results are as follows: Figure 2 and Figure 3 As shown, Figure 2 and Figure 3 The results are summarized in Table 1.

[0071] Table 1 Terahertz characteristic peaks of different sulfides

[0072]

[0073] The results showed that sulfur (S8) had characteristic peaks at 1.41 THz and 1.66 THz; Na2SO3 had characteristic peaks at 1.64, 1.69, 1.84, 1.93, and 2.11 THz, which can be considered as SO3. 2- Characteristic peaks of Na₂SO₄ are observed at 1.64, 1.69, 1.75, 1.86, 1.93, 1.99, 2.07, and 2.11 THz, which can be considered as characteristic peaks of SO₄²⁻. 2- Characteristic peaks. Among them, the increase in the relative value of the 1.75THz and 2.07THz peaks compared to the surrounding peaks, and the 1.86THz peak are the main differences between the characteristic peaks of Na2SO4 and Na2SO3. These characteristic peaks will provide a basis for the morphological identification of residual sulfides in sulfur-fumigated Chinese medicinal materials.

[0074] By comparing the terahertz absorption spectrum of sulfur-fumigated Gastrodia elata with that of sulfur-fumigated Gastrodia elata, it is easy to find that the 1.41 THz peak in sulfur-fumigated Gastrodia elata is consistent with the characteristic peak position of sulfur (S8). This indicates that the new characteristic peak appearing at around 1.41 THz in sulfur-fumigated Gastrodia elata is related to sulfur (S8) residue, and can be used as a qualitative basis for determining whether Gastrodia elata has been fumigated with sulfur.

[0075] 5. Establishment of quantitative identification methods

[0076] 5.1SO3 2- Determination of quantitative characteristic peaks

[0077] A comparison of terahertz absorption spectra of Gastrodia elata samples at different sulfur fumigation times (0h, 2h, 4h, 6h, 8h), as shown in the figure. Figure 4 As shown. By Figure 4 It can be seen that, compared with the un-sulfurized Gastrodia elata (0h), the sulfur-fumigated Gastrodia elata showed new characteristic peaks at 1.41THz and 1.84THz. Furthermore, when the sulfur fumigation time was short, the change in the characteristic peak at 1.41THz was more pronounced, while the change at 1.84THz was relatively weak. Therefore, when the sulfur fumigation time was short, the characteristic peak at 1.41THz was particularly suitable as a qualitative basis for determining whether sulfur-fumigated medicinal materials had undergone sulfur fumigation, while the characteristic peak at 1.84THz might be too weak due to the short fumigation time, making it unsuitable for effectively determining whether the medicinal materials had been fumigated with sulfur.

[0078] In addition, from Figure 4It can also be seen that as the sulfur fumigation time of Gastrodia elata increases, the characteristic peaks at 1.41, 1.64, 1.69, 1.75, 1.84, 1.86 and 1.93 THz increase accordingly, which indicates that there is a quantitative relationship between these characteristic peaks and the sulfur fumigation time.

[0079] As shown in Table 1, the newly appearing characteristic peak at 1.41 THz is consistent with the characteristic peak of sulfur (S8) at 1.41 THz, which can be attributed to the residual sulfur (S8) in the sulfur-fumigated Gastrodia elata; SO3 2- and SO4 2- Characteristic peaks were observed at 1.64 and 1.69 THz, which originated from residual sulfides in the sulfur-fumigated Gastrodia elata, but their specific forms could not be determined and could be used as auxiliary criteria for sulfur fumigation determination; peaks at 1.75, 1.86, and 1.93 THz were associated with SO4. 2- The characteristic peaks are consistent, indicating that the residual sulfides in sulfur-fumigated Chinese medicines are not limited to SO3. 2- In the form of SO4 2- It exists in multiple forms, including SO3. Most importantly, the newly emerging characteristic peak at 1.84 THz is not only related to SO3... 2- The characteristic peak at 1.84 THz is consistent and is SO3. 2- The characteristic peak at 1.84 THz is unique to this species, therefore it can be used as a reference for the SO3 content of sulfur-fumigated Gastrodia elata. 2- Basis for quantitative determination of residual amount.

[0080] Will Figure 4 The characteristic peak areas of Gastrodia elata at 1.84 THz after 0h, 2h, 4h, 6h, and 8h of sulfur fumigation are summarized as follows: Figure 5 ,Depend on Figure 5 It can be seen that as the sulfur fumigation time increases, the characteristic peak area of ​​Gastrodia elata at 1.84 THz also increases, and there is a quantitative relationship between the sulfur fumigation time and the peak area, which lays the foundation for its quantitative analysis.

[0081] 5.2 Determination of SO2 Residue by Pharmacopoeia Method

[0082] The residual SO2 content in *Gastrodia elata* powder samples treated with different sulfur fumigation times (0h, 2h, 4h, 6h, and 8h) was determined according to the acid-base titration method specified in the *Pharmacopoeia of the People's Republic of China* (2025 edition). Samples at each sulfur fumigation time point were subjected to the following independent procedures:

[0083] ① Distillation Conversion: Accurately weigh 20.0 g of Gastrodia elata powder at each sulfur fumigation time point and place it in a three-necked round-bottom flask. Add 400 mL of distilled water and continuously purge with nitrogen gas as the carrier gas at a flow rate of approximately 0.2 L / min. Open the stopcock of the separatory funnel to allow 10 mL of 6 mol / L hydrochloric acid solution to flow into the flask. Immediately heat to boiling and maintain a gentle boil for 1.5 h to decompose the sulfite in the sample and convert it into SO2 gas, which then escapes. Heating is then stopped.

[0084] ②SO2 absorption and conversion: Add 50 mL of 3% hydrogen peroxide solution to the conical flask as the absorbent to absorb the SO2 gas released during distillation. SO2 dissolves in water to form sulfite (SO32-), which is further oxidized by hydrogen peroxide to sulfate (SO42-).

[0085] ③ Acid-base titration: After the absorption solution cools to room temperature, add 3 drops of methyl red ethanol solution as an indicator, and then titrate with 0.01 mol / L sodium hydroxide standard solution until the solution changes from red to yellow and the color does not fade within 20 seconds. Record the volume of sodium hydroxide solution consumed for each sample.

[0086] ④ Blank correction: A blank experiment (i.e., without Chinese medicinal materials, repeating steps ① to ③) is performed simultaneously for each batch of determination to deduct systematic errors that may be introduced by reagents and the environment. Finally, the SO2 residue of each sample is calculated based on the titration difference between the sample and the blank.

[0087] The residual SO2 content in Gastrodia elata after sulfur fumigation for 0h, 2h, 4h, 6h and 8h and the corresponding characteristic peak area at 1.84THz are shown in Table 2.

[0088] Table 2. SO2 residue in sulfur-fumigated Gastrodia elata and its corresponding characteristic peak area at 1.84 THz.

[0089]

[0090] 5.3 Plotting the Standard Curve

[0091] Linear regression analysis was performed using the characteristic peak area at 1.84 THz of Gastrodia elata samples with different sulfur fumigation times in Table 2 as the abscissa (x) and the corresponding SO2 residue measured by the pharmacopoeia method as the ordinate (y).

[0092] The standard curve equation is obtained as: y = 2653.6x - 92.671, and the linear correlation coefficient R0 is... 2 =0.9953 (see Figure 6The curve shows that, within the experimental concentration range, the peak area at 1.84 THz has a good linear relationship with the SO2 residue, and can be used for the quantitative analysis of unknown samples. Moreover, the detection limit of this method is as low as 1 ppm, which can realize the quantitative detection of trace amounts of SO2 residue.

[0093] 6. Example

[0094] The following examples will further illustrate the application effects of the present invention, but are not intended to limit the scope of the present invention.

[0095] Example 1: Rapid detection of self-made sulfur-fumigated Gastrodia elata

[0096] Purchase 500g of fresh Gastrodia elata from Zhaotong, Yunnan Province from Taobao. Take 200g each and 200g for sulfur fumigation for 3h and 5h respectively (method as in 2.1). Use the remaining 100g as a control without sulfur fumigation. Then prepare the test sample according to method 2.2 and measure its terahertz spectrum, such as... Figure 7 As shown.

[0097] Figure 7 The results showed that both sulfur-fumigated samples exhibited distinct characteristic peaks at 1.41 THz and 1.84 THz. Based on the presence of the characteristic peak at 1.41 THz, they can be qualitatively identified as sulfur-fumigated medicinal materials.

[0098] Its peak area at 1.84 THz was measured to be 0.1036 and 0.1601 AU·THz, respectively. -1 .

[0099] Substitute into the standard curve equation to calculate the SO2 residue:

[0100] 3-hour sample: y = 2653.6 × 0.1036 - 92.671 ≈ 182.2 ppm

[0101] 5-hour sample: y = 2653.6 × 0.1601 - 92.671 ≈ 332.2 ppm

[0102] The same batch of samples was validated using the acid-base titration method from the pharmacopoeia. The SO2 residue levels in the sulfur-fumigated samples after 3 hours and 5 hours were measured to be 181.5 ppm and 333.6 ppm, respectively. The results showed a high degree of agreement, and the terahertz method only required about 1 minute, while the acid-base titration method required about 2 hours. Therefore, the measurement method of this invention can not only achieve rapid identification of sulfur-fumigated medicinal materials, but also quantitative measurement of SO2 residues in sulfur-fumigated medicinal materials, with high speed and accuracy.

[0103] Example 2: Blind testing of commercially available Gastrodia elata samples

[0104] Two samples of Gastrodia elata (Sample 1 and Sample 2), each weighing 10g, were randomly purchased from the Chongqing Traditional Chinese Medicine Wholesale Market. Terahertz test samples were prepared using the same sample preparation method (see 2.2), and the terahertz absorption spectra of both samples were measured. Figure 8 As shown. From Figure 8 It can be seen that both sulfur-fumigated samples showed obvious characteristic peaks at 1.41THz and 1.84THz. Based on the appearance of the characteristic peak at 1.41THz, it can be qualitatively determined that they are sulfur-fumigated medicinal materials.

[0105] The peak areas of the characteristic peak at 1.84 THz for the two sulfur-fumigated samples were measured to be 0.09934 and 0.1864 AU·THz, respectively. -1 .

[0106] Substitute into the standard curve equation to calculate the SO2 residue:

[0107] Sample 1: y = 2653.6 × 0.09934 - 92.671 ≈ 170.9 ppm

[0108] Sample 2: y = 2653.6 × 0.1864 - 92.671 ≈ 402.0 ppm

[0109] The same batch of samples was validated using the acid-base titration method in the pharmacopoeia, and the validation results were 169.5 ppm and 403.2 ppm, respectively, which further proves the accuracy of the method of the present invention.

[0110] Example 3: Applicability verification of the method on Codonopsis pilosula samples

[0111] Weigh 500g of fresh Codonopsis pilosula. Take 200g of each and treat with sulfur fumigation for 2h and 4h respectively, with the remaining 100g as a control without sulfur fumigation. Then prepare the test sample according to method 2.2 and measure its terahertz spectrum, such as... Figure 9 As shown. By Figure 9 It can be seen that both samples showed characteristic peaks at 1.41 THz and 1.84 THz, and the peak intensity at 1.84 THz increased with increasing sulfur fumigation time, indicating a clear quantitative relationship. This suggests that the qualitative and quantitative methods established in this invention can be extended to Codonopsis pilosula.

[0112] Example 4: Applicability verification of the method on yam samples

[0113] Weigh 500g of fresh yam. Take 200g of each and treat with sulfur fumigation for 4h and 8h respectively, with the remaining 100g as a control without sulfur fumigation. Then prepare the test sample according to method 2.2 and measure its terahertz spectrum, such as... Figure 10 As shown. By Figure 10It can be seen that characteristic peaks also appeared at 1.41 THz and 1.84 THz for each sulfur-fumigated sample, and the peak intensity at 1.84 THz increased with increasing sulfur fumigation time, indicating a clear quantitative relationship. This shows that the qualitative and quantitative methods established in this invention can be extended to yam.

[0114] 7. Conclusion

[0115] This invention provides a rapid identification method for sulfur-fumigated Chinese medicinal materials and a method for measuring SO2 residues in sulfur-fumigated Chinese medicinal materials. Rapid qualitative identification can be achieved by identifying the characteristic peak of sulfur (S8) at 1.41 THz; and by establishing a method for SO3... 2- The standard curve between the characteristic peak area at 1.84 THz and the SO2 residue level enables the quantitative determination of SO2 residue. This method features simple pretreatment, fast detection speed (within minutes), and high accuracy. It has been validated to be applicable to various Chinese medicinal herbs such as Gastrodia elata, Codonopsis pilosula, and Dioscorea opposita, providing an effective technical means for rapid on-site screening and supervision of the quality of Chinese medicinal materials.

[0116] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit the technical solutions. Those skilled in the art should understand that any modifications or equivalent substitutions to the technical solutions of the present invention without departing from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

Claims

1. A method for rapidly identifying sulfur-fumigated traditional Chinese medicinal materials, characterized in that, The method comprises the following steps: a) preparing a sample of the Chinese medicinal material to be tested and obtaining its terahertz absorption spectrum; b) observing whether the terahertz absorption spectrum has a characteristic peak at 1.41 THz, and if yes, determining that the Chinese medicinal material is sulfured, and if not, determining that the Chinese medicinal material is not sulfured.

2. The method according to claim 1, characterized in that, The preparation of the sample of the Chinese medicinal material to be tested in step a) comprises slicing, drying, crushing, sieving and tabletting the Chinese medicinal material.

3. The method according to claim 1, characterized in that, The Chinese medicinal material comprises Gastrodia elata, Codonopsis pilosula or Dioscorea opposita.

4. A method for measuring the residual amount of SO2 in sulfur-fumigated traditional Chinese medicinal materials, characterized in that, The method comprises the following steps: a) preparing a sample of the Chinese medicinal material to be tested and obtaining its terahertz absorption spectrum; b) measuring the characteristic peak intensity of the terahertz absorption spectrum at 1.84 THz; c) calculating the SO2 residual amount of the Chinese medicinal material to be tested according to a standard curve previously established between the characteristic peak intensity at 1.84 THz and the SO2 residual amount.

5. The method according to claim 4, wherein the method is characterized in that, The preparation of the sample of the Chinese medicinal material to be tested in step a) comprises slicing, drying, crushing, sieving and tabletting the Chinese medicinal material.

6. The method according to claim 5, wherein the method is characterized in that, The sieving is through a 200-mesh sieve.

7. The method according to claim 4, characterized in that, The standard curve is established by the following steps: i. preparing a series of standard samples of Chinese medicinal materials with different sulfuring degrees and known SO2 residual amounts; ii. obtaining the terahertz absorption spectrum of each standard sample and measuring the characteristic peak intensity thereof at 1.84 THz; iii. performing linear fitting with the characteristic peak intensity as the abscissa and the SO2 residual amount of the corresponding standard sample as the ordinate to obtain the standard curve. 8.The method for measuring residual SO2 in sulfur fumigated traditional Chinese medicinal materials according to claim 7, characterized in that, The SO2 residual amount of the standard sample is determined by acid-base titration. 9.The method for measuring residual SO2 in sulfur-fumigated traditional Chinese medicinal materials according to claim 7, characterized in that, The standard curve is y=2653.6x-92.671, wherein y is the SO2 residual amount and x is the characteristic peak area at 1.84 THz.

10. The method for measuring the residual amount of SO2 in sulfur fumigated traditional Chinese medicinal materials according to claim 4, characterized in that, The Chinese medicinal material comprises Gastrodia elata, Codonopsis pilosula or Dioscorea opposita.

Images