A method for rapid quantitative determination of polyvinyl chloride microplastic concentration and humic acid concentration in water
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-05-26
- Publication Date
- 2026-08-14
AI Technical Summary
[0004]为了克服现有技术中聚氯乙烯微塑料与腐殖酸的混合体系光谱重叠导致难以准确定量的问题，本发明提供了一种快速定量水中聚氯乙烯微塑料浓度和腐殖酸浓度的方法
本发明针对聚氯乙烯微塑料与腐殖酸共存时紫外光谱重叠的问题，采用双波长回归方程组法，通过配制不同浓度比例的混合标准溶液并利用多元线性回归建立联立方程组，实现了对两种物质的同时、快速、准确测定。该方法无需物理分离，不受共存物质比例变化的干扰，适用于任意浓度比例的实际水样。为环境水体中微塑料与天然有机质复合污染的监测提供了一种简便、低成本、高准确度的分析手段。
Smart Images
Figure CN122567571A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of chemical analysis and environmental pollution detection technology, specifically relating to a method for rapidly quantifying the concentration of polyvinyl chloride microplastics and humic acid in water. Background Technology
[0002] After use, plastics accumulate in the natural environment and, through physical, chemical, and biological processes, gradually decompose and break down into tiny plastic particles, with particles smaller than 5 mm being called microplastics (MPs). They are widely distributed in marine environments, lakes, rivers, high-altitude snowfields, and polar regions. Due to their small size, large specific surface area, and difficulty in degradation, microplastics can act as carriers of other pollutants or toxic substances during long-distance transport, potentially causing toxic effects on the aquatic environment. Humic acid is a large organic molecule formed by plants and animals through complex biochemical processes involving bacteria, algae, and other microorganisms in the environment, and is ubiquitous in natural ecosystems. The presence of humic acid in natural drinking water sources reduces water mineralization and can also affect the bioavailability of certain toxic pollutants. Humic acid migrates mainly through processes such as adsorption, hydrolysis, complexation, ion exchange, photolysis, and biodegradation, exhibiting a similar migration pattern and pathway to microplastics. This commonality significantly increases the probability of the two encountering and interacting in the environmental medium. The interaction between microplastics and humic acid may alter the migration behavior of both. At the same time, the presence of humic acid can change the toxicity of microplastics, which will directly affect the water quality of various types of water and the health risks of human drinking water.
[0003] Currently, methods for measuring polyvinyl chloride (PVC) microplastics alone mainly include infrared spectroscopy, thermal analysis, and ultraviolet spectrophotometry, while methods for measuring humic acid (HA) mainly include spectrophotometry, volumetric methods, atomic spectroscopy, titration, and colorimetry. However, when both substances co-migrate and exist in a mixed state in aqueous solution, measuring their concentrations often requires separating them for individual detection, which is complex and unsuitable for large-scale testing. Summary of the Invention
[0004] To overcome the problem of inaccurate quantification caused by spectral overlap in the mixed system of polyvinyl chloride microplastics and humic acid in the prior art, this invention provides a method for rapidly quantifying the concentration of polyvinyl chloride microplastics and humic acid in water.
[0005] To achieve the above objectives, the present invention provides the following technical solution: One of the technical solutions of this invention is to provide a method for rapidly quantifying the concentration of polyvinyl chloride microplastics and humic acid in water, comprising the following steps: A series of polyvinyl chloride microplastic-humic acid mixed solutions of known concentrations were prepared, wherein the concentrations of the two substances varied independently within their respective linear ranges. The total absorbance of each mixed solution was measured at wavelengths of 440 nm and 280 nm. Then, with the total absorbance at both wavelengths as the dependent variable and the concentrations of the two substances as the independent variables, a multiple linear regression with intercept was performed to establish the following two-wavelength regression equation system: ; In the dual-wavelength regression equation system b 440 , b 280 The constant term intercepts are at 440 nm and 280 nm; A 440 , A 280 The absorbance of the mixed solution at 440 nm and 280 nm are respectively. k PVC,440 , k HA,440 , k PVC,280 , k HA,280 These are the concentration coefficients; C PVC , C HA The concentrations of polyvinyl chloride microplastics and humic acid in the mixed standard sample; For a mixed water sample containing polyvinyl chloride microplastics and humic acid, it is first diluted or concentrated so that its absorbance falls within the linear range applicable to the above equation. Then, its total absorbance at 440 nm and 280 nm is measured. Substituting these values into the dual-wavelength regression equation set, the concentrations of the two substances can be solved simultaneously.
[0006] Preferably, the specific operational steps of the method for rapidly quantifying the concentration of polyvinyl chloride microplastics and humic acid in water include: (1) Establish a system of two-wavelength regression equations Step 1: Using a NaCl solution of known concentration as the background solution, prepare polyvinyl chloride microplastics with the following concentration ranges sequentially: 0.14~0.16 mg / L, 0.29~0.31 mg / L, 0.74~0.76 mg / L, 1.19~1.21 mg / L, 1.49~1.51 mg / L, 2.99~3.01 mg / L, 7.49~7.51 mg / L, 11.99~12.01 mg / L, and 14.99~1 mg / L. A mixed solution of polyvinyl chloride microplastics and humic acid with concentrations ranging from 0.09 to 0.11 mg / L, 0.19 to 0.21 mg / L, 0.49 to 0.51 mg / L, 0.79 to 0.81 mg / L, 0.99 to 1.01 mg / L, 1.99 to 2.01 mg / L, 4.99 to 5.01 mg / L, 7.99 to 8.01 mg / L, and 9.99 to 10.01 mg / L. Step 2: Measure the total absorbance of the polyvinyl chloride microplastic-humic acid mixed solution at 440 nm and 280 nm respectively. Three parallel samples were set up for each measurement, and the average value was taken to obtain the total absorbance of the mixed solution at each concentration at wavelengths of 440 nm and 280 nm. A 440 , A 280 ; Step 3: Combine all the polyvinyl chloride microplastics and humic acid mixtures. A 440 , A 280 The dependent variable and its corresponding known concentration C PVC , C HA Input the independent variables into the data analysis software, perform multiple linear regression, and obtain the concentration coefficient. k PVC,440 , k HA,440 , k PVC,280 , k HA,280 and intercept b 440 , b 280 Thus, the following set of two-wavelength regression equations is established: ; (2) Calculate the concentrations of polyvinyl chloride microplastics and humic acid in the mixed water sample to be tested. Step 1: Dilute or concentrate the mixed water sample to be tested so that the absorbance of the water sample measured at wavelengths of 440nm and 280nm is within the absorbance range of the corresponding pollutant regression equation set at the obtained wavelengths; Step 2: Measure the total absorbance of the diluted or concentrated water sample at 440 nm and 280 nm. Three parallel samples are used in each measurement, and the average value is taken to obtain the total absorbance values of the water sample at 440 nm and 280 nm. A 440 , A 280 ; Step 3: The measured values... A 440 , A 280 Substitute the two-wavelength regression equations established in step (1) and solve them by matrix inversion or elimination. C PVC , C HA This yields the concentrations of polyvinyl chloride microplastics and humic acid in the original water sample.
[0007] More preferably, the data analysis software includes Origin.
[0008] More preferably, total absorbance A 440 and A 280 The determination methods include ultraviolet-visible spectrophotometry.
[0009] The working principle of this invention is as follows: Based on the additivity of absorbance according to the Lambert-Beer law, when two substances coexist in the same solution, the total absorbance at any wavelength is equal to the sum of the absorbances of each component at that wavelength, and the absorbance of each component is directly proportional to its concentration. Therefore, for the mixed system of polyvinyl chloride microplastics and humic acid, there are linear relationships at wavelengths of 440 nm and 280 nm, respectively. By preparing a series of mixed standard solutions with different concentration ratios, measuring the total absorbance at both wavelengths, and solving the coefficient matrix using multiple linear regression (including the intercept), a set of equations describing the system can be established. For samples with unknown concentrations, only the total absorbance at both wavelengths needs to be measured, and the concentrations of both substances can be simultaneously solved by substituting the measurements into the equations. This method does not require physical separation and can effectively eliminate spectral overlap interference.
[0010] The second technical solution of the present invention provides an application of the above-mentioned method for rapid quantitative determination of polyvinyl chloride microplastic concentration and humic acid concentration in water in environmental water body detection.
[0011] The beneficial technical effects of the present invention are as follows: This invention addresses the issue of overlapping ultraviolet spectra when polyvinyl chloride (PVC) microplastics and humic acid coexist. It employs a dual-wavelength regression equation method, using mixed standard solutions with varying concentrations and establishing a system of simultaneous equations through multiple linear regression. This enables the simultaneous, rapid, and accurate determination of both substances. This method requires no physical separation, is unaffected by changes in the proportion of coexisting substances, and is applicable to real-world water samples with arbitrary concentration ratios. It provides a simple, low-cost, and highly accurate analytical approach for monitoring the combined pollution of microplastics and natural organic matter in environmental water bodies. Attached Figure Description
[0012] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0013] Figure 1 The figures are fitting curves of the actual absorbance value and the regression value in Example 1; where (a) is the fitting curve of the actual absorbance value and the regression value at a wavelength of 440nm, and (b) is the fitting curve of the actual absorbance value and the regression value at a wavelength of 280nm.
[0014] Figure 2 This is the breakthrough curve of polyvinyl chloride microplastics and humic acid under specific column test conditions in Example 3. Detailed Implementation
[0015] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention. It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the present invention.
[0016] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.
[0017] Furthermore, regarding the numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, are also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.
[0018] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar to or equivalent to those described herein may be used in the implementation or testing of this invention.
[0019] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.
[0020] Unless otherwise specified, room temperature in this invention refers to a temperature of 20±10℃.
[0021] Example 1 Establish a set of dual-wavelength regression equations for polyvinyl chloride microplastic-humic acid mixed solutions with gradient concentrations at specific wavelengths: 1. Preparation of standard mixed solutions: Using 1mM NaCl solution as the background solution, a standard mixed stock solution containing 15mg / L polyvinyl chloride microplastics and 10mg / L humic acid was prepared. The standard mixed stock solution was then serially diluted using the background solution to obtain standard mixed solutions containing different concentrations of polyvinyl chloride microplastics and humic acid. The concentrations of polyvinyl chloride microplastics in the mixed solutions were 0.15mg / L, 0.30mg / L, 0.75mg / L, 1.20mg / L, 1.50mg / L, 3.00mg / L, 7.50mg / L, 12.00mg / L, and 15.00mg / L; the corresponding humic acid concentrations were 0.10mg / L, 0.20mg / L, 0.50mg / L, 0.80mg / L, 1.00mg / L, 2.00mg / L, 5.00mg / L, 8.00mg / L, and 10.00mg / L, respectively.
[0022] 2. Absorbance determination: The absorbance of the standard mixed solutions at each concentration was measured at wavelengths of 440 nm and 280 nm using a UV spectrophotometer. Three parallel samples were set up for each measurement, and the average value was taken to obtain the absorbance value of each standard mixed solution at wavelengths of 440 nm and 280 nm.
[0023] 3. Establish a system of regression equations: Input all data into Origin data analysis software, and use the "Regression" function in "Data Analysis" to perform regression analysis using the mixed standard solutions. A 440 , A 280 As the dependent variable, with C PVC , C HAUsing [variable name] as the independent variable, a multiple linear regression with intercept was performed, resulting in the regression equations shown in Table 1. The linear fit between the actual absorbance values and the regression values is shown in [example table]. Figure 1 As shown, (a) is the fitting curve of the actual absorbance value and the regression value at a wavelength of 440 nm, and (b) is the fitting curve of the actual absorbance value and the regression value at a wavelength of 280 nm.
[0024] Table 1. Regression equations for pollutants at specific wavelengths (mixed solutions) Note: A 440 The absorbance of the mixed solution at a wavelength of 440 nm; A 280 The absorbance of the mixed solution at a wavelength of 280 nm; C PVC The concentration of polyvinyl chloride microplastics in the mixed solution is expressed in mg / L. C HA R represents the concentration of humic acid in the mixed solution, in mg / L. 2 This is the linear correlation coefficient.
[0025] Table 1 and Figure 1 The results showed that, within the ranges of 0.15–15 mg / L (PVC) and 0.1–10 mg / L (HA), the absorbance exhibited a good linear additive relationship with the concentrations of the two substances, and this set of regression equations can be used for subsequent quantification of unknown samples.
[0026] Example 2 To verify the accuracy and reliability of the dual-wavelength regression equations for the gradient concentration polyvinyl chloride microplastic-humic acid mixed solution established in Example 1 at a specific wavelength, a recovery experiment was conducted. The specific steps are as follows: 1. Preparation of mixed solutions: Using 1mM NaCl solution as the background solution, a standard mixed stock solution containing 15mg / L polyvinyl chloride microplastics and 10mg / L humic acid was prepared. The standard mixed stock solution was diluted with the background solution to obtain standard mixed solutions containing different concentrations of polyvinyl chloride microplastics and humic acid. The concentrations of polyvinyl chloride microplastics in the mixed solutions were 1.5mg / L, 7.5mg / L, and 12.0mg / L; the corresponding humic acid concentrations were 1.0mg / L, 5.0mg / L, and 8.0mg / L, respectively.
[0027] 2. Absorbance determination: The absorbance of the standard mixed solutions at each concentration was measured at wavelengths of 440 nm and 280 nm using a UV spectrophotometer. Three parallel samples were set up for each measurement, and the average value was taken to obtain the absorbance value of each standard mixed solution at wavelengths of 440 nm and 280 nm.
[0028] 3. Concentration Calculation: The measured concentration will be... A 440 , A 280 Substituting the two-wavelength regression equations established in Example 1, the solution is obtained by substitution and elimination. C PVC , C HA The calculated concentrations of each mixed solution sample were obtained. The actual and calculated contaminant concentrations and recoveries of the mixed solution samples are shown in Table 2.
[0029] Table 2 Comparison of actual and calculated contaminant concentrations in mixed solution samples The results in Table 2 show that the recovery rates of polyvinyl chloride microplastics and humic acid are between 98.0% and 102.0%, respectively. This indicates that the dual-wavelength regression equation set established in this invention has high accuracy for mixed samples of different concentrations and can be used for rapid quantitative detection of polyvinyl chloride microplastic concentration and humic acid concentration in actual water samples.
[0030] Example 3 According to the rapid quantitative test method for polyvinyl chloride (PVC) microplastic concentration and humic acid concentration in water of the present invention, the co-migration behavior of PVC microplastics and humic acid at a constant flow rate in a certain filter media is studied. The specific steps are as follows: 1. Preparation of mixed solution: Using 1mM NaCl solution as background solution, a mixed solution containing 15mg / L polyvinyl chloride microplastics and 10mg / L humic acid was prepared.
[0031] 2. Column Experiment: 20-25 mesh quartz sand was wet-filled into a filter column with an inner diameter of 1.6 cm and a length of 25 cm. The pH was set to 6.6-7.0, and the temperature was room temperature. A peristaltic pump was set at a flow rate of 5 mL / min to pump the prepared mixed solution into the filter column. Under these experimental conditions (flow rate 5 mL / min, column volume approximately 50 mL), preliminary experiments showed that the effluent concentration stabilized after approximately 10-12 minutes of bubbling. A 14-minute bubbling period ensured that adsorption equilibrium or a breakthrough plateau was reached within the column before switching to the background solution, facilitating the acquisition of a complete breakthrough curve. In the formal experiment, the mixed solution was continuously bubbled for 14 minutes, followed by the background solution. The entire experimental process lasted 28 minutes, with water samples collected from the filter column every 56 seconds throughout the experiment.
[0032] 3. Absorbance measurement: The absorbance of each effluent water sample was measured at wavelengths of 440 nm and 280 nm using an ultraviolet spectrophotometer.
[0033] 4. Concentration Calculation: The absorbance measured at each wavelength for each water sample was substituted into the regression equations for pollutants at each wavelength in Table 1 obtained in Example 1 to calculate the concentrations of polyvinyl chloride microplastics and humic acid in the water samples collected at each time point. The results are as follows: Figure 2 As shown.
[0034] from Figure 2 As can be seen from the above, the method proposed in this invention can detect the concentrations of polyvinyl chloride microplastics and humic acid in mixed water samples, and can be used for research on the co-migration of pollutants and evaluation of the removal efficiency of filtration processes. This method is simple to operate, low in cost, and suitable for large-scale testing.
[0035] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.
Claims
1. A method for rapidly quantifying the concentration of polyvinyl chloride microplastics and humic acid in water, characterized in that, Includes the following steps: A series of polyvinyl chloride microplastic-humic acid mixed solutions of known concentrations were prepared, wherein the concentrations of the two substances varied independently within their respective linear ranges. The total absorbance of each mixed solution was measured at wavelengths of 440 nm and 280 nm. Then, with the total absorbance at both wavelengths as the dependent variable and the concentrations of the two substances as the independent variables, a multiple linear regression with intercept was performed to establish the following two-wavelength regression equation system: ； In the dual-wavelength regression equation system b 440 , b 280 The constant term intercepts are at 440 nm and 280 nm; A 440 , A 280 The absorbance of the mixed solution at 440 nm and 280 nm are respectively. k PVC,440 , k HA,440 , k PVC,280 , k HA,280 These are the concentration coefficients; C PVC , C HA The concentrations of polyvinyl chloride microplastics and humic acid in the mixed standard sample; For a mixed water sample containing polyvinyl chloride microplastics and humic acid, it is first diluted or concentrated so that its absorbance falls within the linear range applicable to the above equation. Then, its total absorbance at 440 nm and 280 nm is measured. Substituting these values into the dual-wavelength regression equation set, the concentrations of the two substances can be solved simultaneously.
2. The method for rapidly quantifying the concentration of polyvinyl chloride microplastics and humic acid in water according to claim 1, characterized in that, The specific operating steps include: (1) Establish a system of two-wavelength regression equations Step 1: Using a NaCl solution of known concentration as the background solution, prepare polyvinyl chloride microplastics with the following concentration ranges sequentially: 0.14~0.16 mg / L, 0.29~0.31 mg / L, 0.74~0.76 mg / L, 1.19~1.21 mg / L, 1.49~1.51 mg / L, 2.99~3.01 mg / L, 7.49~7.51 mg / L, 11.99~12.01 mg / L, and 14.99~1 mg / L. A mixed solution of polyvinyl chloride microplastics and humic acid with concentrations ranging from 0.09 to 0.11 mg / L, 0.19 to 0.21 mg / L, 0.49 to 0.51 mg / L, 0.79 to 0.81 mg / L, 0.99 to 1.01 mg / L, 1.99 to 2.01 mg / L, 4.99 to 5.01 mg / L, 7.99 to 8.01 mg / L, and 9.99 to 10.01 mg / L. Step 2: Measure the total absorbance of the polyvinyl chloride microplastic-humic acid mixed solution at 440 nm and 280 nm respectively. Three parallel samples were set up for each measurement, and the average value was taken to obtain the total absorbance of the mixed solution at each concentration at wavelengths of 440 nm and 280 nm. A 440 , A 280 ; Step 3: Combine all the polyvinyl chloride microplastics and humic acid mixtures. A 440 , A 280 The dependent variable and its corresponding known concentration C PVC , C HA Input the independent variables into the data analysis software, perform multiple linear regression, and obtain the concentration coefficient. k PVC,440 , k HA,440 , k PVC,280 , k HA,280 and intercept b 440 , b 280 Thus, the following set of two-wavelength regression equations is established: ； (2) Calculate the concentrations of polyvinyl chloride microplastics and humic acid in the mixed water sample to be tested. Step 1: Dilute or concentrate the mixed water sample to be tested so that the absorbance of the water sample measured at wavelengths of 440nm and 280nm is within the absorbance range of the corresponding pollutant regression equation set at the obtained wavelengths; Step 2: Measure the total absorbance of the diluted or concentrated water sample at 440 nm and 280 nm. Three parallel samples are used in each measurement, and the average value is taken to obtain the total absorbance values of the water sample at 440 nm and 280 nm. A 440 , A 280 ; Step 3: The measured values... A 440 , A 280 Substitute the two-wavelength regression equations established in step (1) and solve them by matrix inversion or elimination. C PVC , C HA This yields the concentrations of polyvinyl chloride microplastics and humic acid in the original water sample.
3. The method for rapidly quantifying the concentration of polyvinyl chloride microplastics and humic acid in water according to claim 2, characterized in that, The data analysis software includes Origin.
4. The method for rapidly quantifying the concentration of polyvinyl chloride microplastics and humic acid in water according to claim 1 or 2, characterized in that, Total absorbance A 440 and A 280 The determination methods include ultraviolet-visible spectrophotometry.
5. The application of the method for rapid quantitative determination of polyvinyl chloride microplastic concentration and humic acid concentration in water according to any one of claims 1 to 4 in the detection of environmental water bodies.