Abstract
Arsenic (As) accumulated in genuine medicinal materials will not only deteriorate the original medicinal properties of the medicinal materials but also harm the eater’s body. In this study, inductively coupled plasma mass spectrometry (ICP-MS) technology was used to investigate the total As content of honeysuckle in four regions, namely Fengqiu, Henan, Xinmi, Shandong, and Julu, Hebei, as well as the speciation and content of As in the roots, stems, and leaves of honeysuckle. This research shows that the total As content of honeysuckle in the four regions was 0.25–0.3 mg/kg. At 1.5 mol/L H3PO4, 200 W, we performed ultrasonic extraction for 30 min at 60°C and adopted high performance liquid chromatography-inductively coupled plasma mass spectrometry (HPLC-ICP-MS) to analyze the As speciation of honeysuckle plants. The soil As speciation mainly exists in the form of As(v). In the medicinal part of honeysuckle, the amount of different As speciation is ranked in the descending order as As(v) > As(iii) > dimethyl As acid > monomethyl As acid > AsC. As(v) is the main speciation, accounting for 64.5% of the total, followed by the most toxic As(iii), which is 18.8%. As(v) absorbed by the root system of honeysuckle from the soil tends to transform to As(iii) when transported upwards, and the transformation process mainly occurs in the roots.
1 Introduction
As a treasure of the traditional Chinese culture, traditional Chinese medicine is one of China’s few industries with international competitive advantages. With the rapid development of industrialization, heavy metal pollution worsens, and Chinese medicinal materials have also suffered greatly. Excessive heavy metals have become a key issue that affects the quality and reputation of traditional Chinese medicine and hinder the global development of traditional Chinese medicine [1,2,3].
Arsenic (As) is a metal-like element with similar physical and chemical properties as metals, which is also classified as heavy metal in the environment. As is a highly toxic environmental pollutant, which is not essential for plants. Chinese herbal medicine can accumulate As through the growth environment and conditions (such as soil/plant absorption, irrigation water, and atmospheric deposition). In addition, As can also enter traditional Chinese medicine through drying, storage, transportation, and manufacturing processes [4,5]. The 2015 Chinese Pharmacopoeia stipulates that the As concentration in Chinese herbal medicines cannot exceed 2 mg/kg; ISO stipulates that the As concentration in Chinese herbal medicines cannot exceed 4 mg/kg [6]. A number of studies have shown that As in many Chinese herbal medicines has exceeded the limit. However, As toxicity largely depends on its chemical speciation. As displays different toxicity depending on speciation. As in the environment includes inorganic As As2O3, As2O5, etc., and organic As including monomethyl As acid (MMA) and dimethyl As acid (DMA) and trimethyl As acid (TMA), while in seafood, it is mainly arsenobetaine (AsB) and arsenocholine (AsC). The toxicity of As to organisms relates to the concentration, speciation, bioavailability, and ingestion mode of arsenic. Generally speaking, inorganic As is more toxic than organic arsenic, and trivalent As is more toxic than pentavalent arsenic [7,8]. The information based on the total As concentration may be insufficient. In order to better understand the absorption and metabolism of As in traditional Chinese medicine, it is essential to determine the As speciation.
Honeysuckle is the dry bud or first bloom of the honeysuckle family plant Lonicera japonica. As one of the important and precious Chinese medicinal materials in China, it has the effect of clearing heat and detoxifying, dispelling wind and heat [6]. Because of its unique fragrance and health functions, some Asian and European countries consume Chinese herbal medicine as a herbal tea beverage [9,10]. Nowadays, honeysuckle is commonly used as a bulk Chinese medicinal material but its product quality has several issues. Therefore, using honeysuckle as a traditional Chinese medicine plant sample, it is typical to conduct a scientific evaluation of the impact of heavy metal pollution on the quality of medicinal materials and explore the reduction of heavy metal accumulation in the medicinal parts of plants. There are many literature reports studying honeysuckle under heavy metal stress, and the results show that honeysuckle has a certain super-accumulation ability against some heavy metals, and when the heavy metal stress exceeds a certain range, heavy metals exert a huge impact on the physiological and pharmacological effects of honeysuckle [11,12].
At present, the commonly used methods for As extraction include hot extraction [13], ultrasonic-assisted extraction [14], and microwave-assisted extraction [15]. There are many analytical techniques for As speciation. High-performance liquid chromatography with the advantages of low detection limit, high sensitivity, and wide linear range is currently widely used in the analysis of As speciation in aquatic products [16,17], fungi [18,19], Chinese medicinal materials [13], birds [20], and a variety of substrates. For example, Fen et al. used HPLC-ICP-MS to analyze six As speciation in birds in mining areas [20], and Liang et al. used HPLC-ICP-MS to simultaneously determine six As speciation in the medicinal material Semen Cuscutae [13].
At present, there are many research studies on Chinese medicinal materials, but research on the whole plant and the overall research on the living environmental soil are rare. In this study, the total As content was determined by ICP-MS, and As speciation of honeysuckle in different genuine regions is analyzed by HPLC-ICP-MS. The As speciation in the whole honeysuckle plant (including the flower roots, stems, and leaves) and the local soil is analyzed to enable a clearer understanding of the migration process of different speciation of As in the whole plant.
2 Experimental materials and methods
2.1 Sample collection
Honeysuckle was purchased from Fengqiu, Henan, Xinmi, Henan, Linyi, Shandong, and Julu, Hebei. The whole plant (rhizome and leaves) and soil were collected from Xinmi, Henan. Before analysis, the plant samples were rinsed thoroughly with tap water, then rinsed with deionized water three times and dried in an oven at 70°C, crushed, and passed through a 100 mesh sieve. The soil samples were dried at room temperature and ground through a 100 mesh sieve.
2.2 Apparatus and reagents
The following instruments were used in the work: Analytical Balances (METTLER AT201, Mettler Instruments, Switzerland); Ultrasonic cleaner (KH-250DB, Kunshan Hechuang Ultrasonic Instrument Co., Ltd, Kunshan, China.); Centrifuge (TG16-WS, Shanghai Mingyuan Industrial Co., Ltd, Shanghai, China); Milli-Q plus ultrapure water system (Millipore Corporation, USA); HT-200 electric heating plate (Guangzhou Yide Precision Scientific Instrument Co., Ltd, Guangzhou, China); electric heating constant temperature blast drying oven DHG-9143A (Shanghai Xinyi Instrument Co., Ltd. Shanghai, China); FD-1A-50 freeze dryer (Beijing Hongda Hengye Technology Co., Ltd. Ningbo, China); PHSJ-3F pH meter (Shanghai Xinyi Instrument Co., Ltd, Shanghai, China); inductively coupled plasma mass spectrometer (PerkinElmer NexION 300X, PerkinElmer, USA); high performance liquid chromatograph (Waters, USA); anion exchange column with guard column (Hamilton PRP-X100, 250 mm × 4.1 mm, 10 μm); EB850 Grinding machine (Shanghai Zhikai Powder Machinery Manufacturing Co., Ltd., Shanghai, China).
H3PO4, (NH4)CO3, NaH2PO4, and K2HPO4 were analytically pure; HNO3 (70%) and H2O2 (30%) were of MOS grade (Metal-oxide-semiconductor); and CH3OH was of chromatographic grade. All were purchased from Beijing Chemical Reagent Company. Germanium (Ge) standard solution (1,000 μg/mL) was from the National Nonferrous Metals and Materials Analysis and Testing Center, Beijing, China, and As standard solution (1,000 μg/mL) was from National Nonferrous Metals and Materials Analysis and Testing Center, Beijing, China. The following five As standard reference materials were purchased from the Chinese Academy of Metrology, Beijing, China: arsenate reference materials (As(v), GBW08667, 17.5 ± 0.4 μg/g); arsenite standard material (As(iii), GBW08666, 75.7 ± 1.2 μg/g); monomethyl arsenic acid standard material (MMA, GBW08668, 25.1 ± 0.8 μg/g); dimethyl arsenic acid standard material (DMA, GBW08669, 52.9 ± 1.8 μg/g); arsenic choline standard material (AsC, GBW 08671, 28.0 ± 1.1 μg/g).
2.3 ICP-MS total As test method
2.3.1 Standard solution preparation
The As standard solution was diluted with 2% HNO3 into a series of standard solutions of 0.1, 0.5, 1, 5, 10, 50, and 100 μg/L.
2.3.2 Internal standard solution preparation
The Ge standard solution was diluted with 2% HNO3 into 40 μg/L standard solutions.
2.3.3 Sample solution preparation
About 0.1 g plant sample was accurately weighed and 8 mL HNO3 and 2 mL H2O2 were added; then 0.01 g soil sample was accurately weighed and 8 mL HNO3, 2 mL HClO4, and 2 mL H2O2, were added. The mixture was placed in the digestion tank overnight for predigestion, and then it was put in an oven and digested at 150°C for 5 h. After the digestion was completed, it was placed on a 170°C electric hot plate to heat the solution; then the acid was discharged until the solution was about 1 mL. Later, the solution was transferred with 2% HNO3 and filled to 10 mL, mixed well, and analyzed for the total As content.
During measurement of arsenic by ICP-MS, polyatomic interference, mainly argon (40), chlorine (35) formation (ArCl 75), interferes with the detection of arsenic. This experiment uses the collision reaction cell mode, in which the reactant gas consists of 7.8% mixed gas of He and H2, and the collision gas flow rate is 3.30 mL/min, thereby eliminating polyatomic interference. Organic small molecules and inorganic salts have an impact on the ICP-MS signal. The mass range of inorganic mass spectrometry elements is 5-255. 74Ge solution is used as internal standards to calibrate instrument drift and sample matrix interference in online form.
2.4 HPLC-ICP-MS analysis of As speciation
2.4.1 Standard solution preparation
The mobile phase is used to dilute the As mixed mother liquor solution into a series of standard solutions of 0.5, 1, 5, 10, 50, and 100 μg/L.
2.4.2 Internal standard solution preparation
The Ge standard solution is diluted with 2% HNO3 into 40 μg/L standard solutions.
2.4.3 Sample solution preparation
About 0.5 g of the sample was accurately weighed into a 50 mL centrifuge tube; then 15 mL of 1.5 mol/L H3PO4 extraction solution was added for the first time. The centrifuge tube was heated in a water bath at 80°C for 1 h, then sonicated for 30 min, centrifuged for 10 min (4,000 rpm), and transferred to a 50 mL centrifuge tube. Sonication was repeated twice and a 5 mL extraction solution was added each time, and finally, the supernatants were combined to fill the volume to 25 mL. The centrifuge tube was placed in a freeze dryer to dry. Before analyzing the As speciation, it was dissolved to 5 mL with 20 mmol/L NaH2PO4 and K2HPO4 (pH = 5.8) mobile phase solution, and the solution was screened through a 0.22 μm filter membrane. The working conditions of HPLC mass spectrometry are shown in Table 1.
Working conditions of HPLC mass spectrometry
| Conditions | |
|---|---|
| HPLC system | |
| Column | Hamilton PRP-X100, 10 μm diam. Particles, 4.1 mm i.d. × 250 mm length |
| Mobile phase, flows | 20 mmol/L NaH2PO4 and K2HPO4 (pH = 5.8) |
| Separation scheme | Isocratic |
| Injection volume | 100 μL |
| Column temp. | 20°C |
| Flow rate | 1 mL/min |
| ICP-MS | |
| Monitored | 75As |
| R.F. power | 1,200 W |
| Atomizer flow rate | 0.8 L/min |
| Auxiliary air flow rate | 0.8 L/min |
| Reaction gas | 7.8% mixed gas of He and H2 |
| Intake voltage | −110 eV |
| Sampling depth | 140 mm |
| Collider airflow | 3.30 mL/min |
2.5 Data processing and analysis
SPSS and Origin software were used to process and analyze experimental data.
3 Results and discussion
3.1 Determination of total As concentration
According to the experimental method given in Section 2.3, the total As content of honeysuckle plants (flowers, roots, stems, and leaves) and soil samples were detected. The results are shown in Table 2. The measured value is the mean ± standard deviation (
ICP-MS determination of the total As content in samples (mg/kg) (n = 3)
| Sample site | Soil | Root | Stem | Leave | Honeysuckle |
|---|---|---|---|---|---|
| Fengqiu (Henan province) | 10.35 ± 1.81 | 2.26 ± 0.11 | 0.17 ± 0.12 | 0.26 ± 0.25 | 0.25 ± 0.11 |
| Xinmi (Henan province) | 17.97 ± 1.00 | 3.40 ± 3.83 | 0.09 ± 0.07 | 0.33 ± 0.10 | 0.27 ± 0.38 |
| Julu (Hebei province) | — | — | — | — | 0.23 ± 0.20* |
| Linyi (Shandong province) | — | — | — | — | 0.30 ± 0.54* |
Note: — represents no experiment.
*Significant differences in the As content of honeysuckle in different regions (P < 0.05).
It can be seen from Table 2 that, for the samples from Fengqiu, Henna, the total As content in the soil is 10.4 mg/kg, the total As content in the honeysuckle plant is 2.93 mg/kg, and the total As content in the flower is 0.245 mg/kg; for the samples from Xinmi, Henan, the total As content in the soil is 18.0 mg/kg, the total As content in the honeysuckle plant is 4.12 mg/kg, and the total As content in the honeysuckle is 0.267 mg/kg, indicating that only part of the As in the soil will be absorbed to honeysuckle.
The total amount of As in soil is much higher than that in plant samples. The honeysuckle in Linyi, Shandong Province, has the highest total amount of arsenic, with a concentration of 0.301 mg/kg, but none of them exceeds the limit value of the Chinese Pharmacopoeia (2 mg/kg), so the honeysuckle producing areas from the selected regions are not seriously polluted by arsenic. In the plant samples, the content of As is the highest in the root, followed by the leaves, and the stem has the lowest content. It is speculated that the stem mainly transmits nutrients and does not absorb heavy metal arsenic. However, As is mainly concentrated in the roots, and plants have poor ability to transport heavy metal As to flowers and leaves.
About 0.1 g of Xinmi honeysuckle sample was accurately weighed and the As standard solution was added. After digestion, ICP-MS was performed to determine the background value and the indexed value. Then the index recovery rate was calculated, and three parallel indexed concentrations were prepared. The precision and recovery rates are shown in Table 3. The sample index recovery rate was 100%, and the relative standard deviation RSD was 3.13%, indicating that the method has good precision.
ICP-MS sample addition and recovery experimental data (n = 3)
| Element | Background values (mg/L) | Spiking values (mg/L) | Experimental values after spiking (mg/L) | Spiked recovery (%) |
|---|---|---|---|---|
| 75As | 0.27 ± 0.38 | 1.0 | 1.27 ± 2.10 | 100.20 ± 3.13 |
3.2 Determination of As speciation
3.2.1 Standard curve and detection limit
It has been verified that the mixed solution, of 20 mM NaH2PO4 and K2HPO4 at pH 5.8 can well separate the five As speciation (As(iii), As(v), DMA, MMA, AsC). Figure 1a shows the spectrogram of the mixed standard solution of 50 μg/L As speciation after eluting isocratically by HPLC, and the spectra were obtained by ICP-MS.
Spectrogram of As speciation AsC, As(iii), DMA, MMA, As(v): (a) 10 μg/L mixed standard solution of As speciation; and (b)spectrogram of honeysuckle flower in Fengqiu area.
The mixed standard solution series of 1, 5, 10, 50, 100 μg/L were measured according to the test method plot, the standard curve with the mass concentration of the five As speciation as the abscissa, and the corresponding chromatographic peak area as the ordinate. The results show that the linear ranges of the five As speciation are all 5–100 μg/L, and the linear regression equation and correlation coefficient are shown in Table 4.
Linear parameters and detection limits of five As speciation
| As speciation | Equation of linear regression | Correlation coefficient | Detection limit ρ/(μg/L) |
|---|---|---|---|
| As(iii) | y = 252.39x − 35.9 | R² = 0.9999 | 0.64 |
| As(v) | y = 309.36x + 234.89 | R² = 0.9984 | 0.31 |
| DMA | y = 272.86x − 14.971 | R² = 0.9999 | 0.37 |
| MMA | y = 246.31x − 45.324 | R² = 0.9998 | 0.42 |
| AsC | y = 297.33x + 95.623 | R² = 0.9987 | 0.62 |
The detection limit (3S/N) of the five As speciation was calculated with three times signal-to-noise ratio (S/N), and the results are shown in Table 4.
3.2.2 Precision and recovery experiment
About 10 μg/L mixed standard solution was used for determination (n = 3), and the RSD values of As(iii), As(v), DMA, MMA, AsC are 2.1, 2.2, 5.6, 3.4, 1.8%, respectively, indicating that this method has good precision. According to the experimental method, the standard experiment (n = 3) with a 50 μg/L concentration was carried out on the sample flowers in the Hebei area. The index recovery rates of the five As speciation were in the range of 89.52–104.11%. The results are shown in Table 5.
Honeysuckle measurement values and index recovery rates in the Hebei area (n = 3)
| Background values (μg/L) | Spiking values (μg/L) | Experimental values after spiking (μg/L) | Spiked recovery (%) | |
|---|---|---|---|---|
| As(iii) | 0.23 ± 0.02 | 50 | 44.76 ± 0.17 | 89.52 ± 2.13 |
| As(v) | 1.03 ± 0.06 | 50 | 49.32 ± 0.33 | 98.65 ± 2.20 |
| DMA | 1.18 ± 0.12 | 50 | 49.48 ± 0.31 | 98.95 ± 5.61 |
| MMA | 0.73 ± 0.04 | 50 | 52.05 ± 0.16 | 104.11 ± 3.21 |
| AsC | 0.45 ± 0.12 | 50 | 46.99 ± 0.02 | 93.97 ± 1.85 |
3.2.3 Optimization of extraction conditions
Common extraction methods include ultrapure water, low-concentration acid, methanol–water and other systems. Three extractants of water, 1 mol/L phosphoric acid, and methanol:water (1:1, v-v) were selected to treat various parts of honeysuckle produced in Xinmi and the soil. The extraction effects of the five speciation of As compounds are shown in Table 6.
Research data of extraction rates of different extractants (n = 3)
| Sample | Extraction rate (%) | ||
|---|---|---|---|
| Ultrapure water | 1 mol/L H3PO4 | Methanol:water (1:1) | |
| Honeysuckle | 32.1 ± 0.8 | 49.8 ± 1.2 | 13.0 ± 0.6 |
| Root | 4.0 ± 2.2 | 26.5 ± 0.8 | 0.9 ± 0.7 |
| Stem | 8.2 ± 2.4 | 29.9 ± 0.1 | 12.6 ± 0.3 |
| Leave | 48.2 ± 0.3 | 26.0 ± 0.8 | 7.2 ± 0.9 |
| Soil | 2.3 ± 1.2 | 40.3 ± 0.5 | 0.5 ± 3.5 |
Extraction rate = the total amount of As digested by the extracted sample/the total amount of As digested by the sample directly.
Among the three different extractants, the extraction effect of phosphoric acid is relatively good, so the effect of different concentrations of phosphoric acid on the sample is further verified (see Table 7). As the concentration of the extraction solution increases, the extraction efficiency also increases, with the extraction rate reaching a maximum at 1.5 mol/L.
Research data on As extraction with different concentrations of phosphoric acid (n = 3)
| H3PO4 concentration (mol/L) | Extraction rate (%) | |||
|---|---|---|---|---|
| 0.5 | 1 | 1.5 | 2 | |
| Honeysuckle | 23.3 ± 0.2 | 49.8 ± 1.2 | 84.0 ± 1.8 | 74.9 ± 0.9 |
| Root | 14.9 ± 0.5 | 26.5 ± 0.5 | 43.0 ± 1.9 | 35.7 ± 0.6 |
| Stem | 18.7 ± 0.1 | 29.9 ± 0.4 | 59.2 ± 1.1 | 42.0 ± 0.6 |
| Leave | 21.4 ± 0.2 | 26.0 ± 0.9 | 67.3 ± 2.5 | 36.9 ± 0.1 |
| Soil | 27.1 ± 0.9 | 40.3 ± 2.3 | 59.4 ± 1.0 | 51.8 ± 1.5 |
3.2.4 Analysis of sample As speciation
According to the experimental method, the As speciation in the flower root, stem, leaf, and soil samples in the Fengqiu area was determined. The As speciation spectrogram of the sample is shown in Figure 1b. The results of each sample speciation are shown in Table 8.
Speciation data of As in samples (n = 3)
| Sample | Extracted As compounds ω/(mg/kg) | |||||||
|---|---|---|---|---|---|---|---|---|
| AsC | As(iii) | DMA | MMA | As(v) | Sum of As species | Total arsenic | Extraction rate (%) | |
| Honeysuckle | 0.003 ± 0.032 | 0.035 ± 0.225 | 0.018 ± 0.151 | 0.010 ± 0.120 | 0.120 ± 0.043 | 0.19 ± 0.45 | 0.24 ± 0.11 | 79.2 ± 1.3 |
| Root | — | 0.112 ± 0.123 | 0.008 ± 0.082 | 0.013 ± 0.034 | 0.314 ± 0.214 | 0.45 ± 0.52 | 2.26 ± 0.11 | 19.9 ± 0.8 |
| Stem | — | 0.012 ± 0.050 | 0.008 ± 0.232 | 0.006 ± 0.083 | 0.074 ± 0.123 | 0.10 ± 0.22 | 0.17 ± 0.12 | 58.8 ± 1.1 |
| Leaves | 0.052 ± 0.110 | 0.011 ± 0.317 | 0.006 ± 0.124 | 0.064 ± 0.043 | 0.040 ± 0.071 | 0.17 ± 0.21 | 0.26 ± 0.25 | 65.4 ± 2.5 |
| Soil | ND | 0.064 ± 0.033 | ND | ND | 2.55 ± 0.08 | 2.61 ± 0.12 | 10.4 ± 1.8 | 25.1 ± 2.3 |
ND: Not detected.
—: Below the detection limit.
A study on As speciation was carried out with soil and plants in Fengqiu, Henan Province, as samples. The main As speciation in soil was As(v), accounting for 97.6%. The root As(v) in plant samples was as high as 70.3%, followed by the proportion of As(v) in honeysuckle, which was about 64.5%. As the soil contains a lot of As(v), plants absorb more pentavalent arsenic.
The proportion of As(iii) in roots, stems, leaves, and flowers is higher than that in soil samples. The roots have the highest proportion of As(iii), reaching 25.1%, followed by 18.8% in flowers. Plants absorb As(v) from the soil, and a large amount of As(iii) is reduced in the roots, which is mainly accumulated on the flowers of medicinal parts through the transmission of stems. As(iii) is more toxic than As(v). From a biological point of view, As is not an essential element for plant growth, and As is extremely toxic to plants when it is excessive. As(v) is a chemical analogue of phosphate. Both As and phosphorus belong to the VA elements in the periodic table, which have similar structures and properties. As(v) can replace phosphoric acid in the energy transfer reaction of phosphorylation, thereby uncoupling the oxidative phosphorylation progress, inhibiting the production of high-energy phosphate bond adenosine triphosphate, and then interfering with energy metabolism. The presence of As in plants in the form of As(iii) can prevent As(v) from destroying the oxidative phosphorylation process [21,22]. Other scholars believe that the conversion of As(v) to As(iii) in plants may relate to the reducing thiols of glutathione in plants, which can convert As(v) into As through desulfurization reactions (iii) [23,24]. This plant has its own special detoxification mechanism, and the study of As speciation in plants such as Pteris nervosa with As super-enrichment also shows a similar phenomenon [25].
The content of organic As in soil is very low and has not been detected. In flowers and leaves, various speciation of organic As (AsC, DMA, MMA) is detected, and the proportion of organic As in flowers reaches 16.7%.
The toxicity of arsenic to organisms is not only related to the concentration of arsenic but also related to its speciation. Excessive heavy metals will not only disturb the various physiological and biochemical processes in the medicinal plants but also reduce the therapeutic effect of traditional Chinese medicine. Drugs containing heavy metals are an important part of Chinese medicine and have a long history. Because of their remarkable and unique curative effects, they are still widely used today. For example, the prescription contains realgar (As2S2) Angong Niuhuang Pills, Niuhuang Qingxin Pills, Niuhuang Jiedu tablets, etc. Therefore, when formulating the limit standards for heavy metals in traditional Chinese medicine, it is necessary to detect the content of heavy metals, and more importantly, to detect the speciation of heavy metals. In the Chinese Pharmacopoeia, the concentration of heavy metals is determined by atomic absorption spectrometry. This study shows that ICP-MS can quickly detect the total amount of As, and HPLC-ICP-MS can detect the content of five speciation of arsenic in medicinal materials. In the analysis of As speciation, sample pretreatment is the basis, and the method of extracting As from solid samples is the key; unfortunately, so far there is no effective method. A strong extractant may change the speciation of As; a weak extractant can ensure that the speciation of As is not changed, but the extraction rate is not high. Therefore, a simpler and faster method of heavy metal speciation analysis is yet to be developed.
In China, researchers are gradually establishing new standards and new methods for evaluating the safety of heavy metals in traditional Chinese medicine, especially changing the one-sided toxicity evaluation model in which elements replace compounds. HPLC-ICP-MS analysis technology has outstanding advantages in quality control and regulating certain potential harmful contents in medicines.
4 Conclusion
For honeysuckle in the four origins of genuine honeysuckle–Fengqiu, Henan, Xinmi, Henan, Linyi, Shandong, and Julu, Hebei, there are significant differences in the As content in honeysuckle between Hebei and Shandong. The As content is in line with ISO regulations that the concentration of As in Chinese medicinal materials cannot exceed 4 mg/kg. HPLC-ICP-MS research shows that all five speciation exist in the medicinal parts of honeysuckle, and the proportion of inorganic As compounds is high. Although the highly toxic As(iii) does not excessively accumulate in the flower, some As(iii) generated from the root is still transferred here. This study provides a scientific basis for the quality control of Chinese medicinal materials and helps to study the morphological distribution and transport laws of As in honeysuckle plants.
Acknowledgment
Thanks for the guidance of Mr. Li Bai, Institute of High Energy Physics, Chinese Academy of Sciences.
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Funding information: This research was financially supported by the National Natural Science Foundation of China (Grant No. 11975048) and Beijing Union University Graduate Program (Grant No. YZ2020K001).
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Author contributions: Congnan Peng and Juntong Zhou: writing – original draft, Yaxuan Sun: methodology, Hang Yin: data curation, Yuxin Chen and LiYao: validation, Kailin Qi: formal analysis, Qing Huo: supervision, conceptualization, and Fei Xie: project management.
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Conflict of interest: The authors have no conflicts of interest to declare.
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Ethical approval: The conducted research is not related to either human or animal use.
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Data availability statement: N/A.
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