Method for detecting content of elements in carbonized resin

Abstract

The invention provides a method for detecting the content of elements in carbonized resin. The method comprises the steps of resin pretreatment, instrument tuning, standard curve drawing, sample detection and the like. The method comprises the following steps: firstly, transferring a certain amount of dry carbonized resin into a cleaned PFA digestion tank, adding high-purity mixed acid, setting a segmented heating program to start microwave digestion, cooling to room temperature after digestion is completed, adding a proper amount of ultrapure water to dilute a digestion solution, and adding an internal standard solution and a chemical additive to obtain a to-be-detected sample solution; preparing a multi-element mixed standard solution according to the sample element types, adding the standard solution into the sample solution, and measuring the signal intensity ratio R of the to-be-measured element to the internal standard in each solution; and drawing a standard curve by taking the labeling concentration as a horizontal coordinate and R as a vertical coordinate, correcting the standard curve, and detecting the sample to be detected. The method is used for detecting the content of elements in carbonized resin, the carbonized resin is digested through microwaves, and the obtained solution is clear and can be directly subjected to ICP-OES (Inductively Coupled Plasma-Optical Emission Spectrometer) detection.

Description

Technical Field

[0001] This invention belongs to the field of elemental analysis and testing technology, specifically a method for detecting the elemental content in carbonized resin. Background Technology

[0002] In modern chemical, nuclear energy, and electronics industries, carbonized resins are important materials, and the detection of their elemental content is crucial for product quality control and performance evaluation. The presence of different elements can affect the physicochemical properties of carbonized resins, thereby influencing their performance in practical applications. Therefore, developing a rapid, accurate, and reliable detection method is a current research focus.

[0003] The current challenges in the digestion and detection of carbonized resin are as follows: First, the matrix effect causes detection interference: carbonized resin contains a high carbon matrix, and the residual organic carbon after digestion will inhibit the excitation efficiency of some elements in ICP-OES, especially low ionization energy elements such as Li, Na, K and elements that easily form carbides such as Cr, Fe, Ni, which will lead to signal intensity attenuation and lower detection results.

[0004] Secondly, there's the recovery rate of specific elements: such as volatile elements Hg and As: During the digestion of carbonized resin, Hg has a high vapor pressure, and the recovery rate under conventional digestion conditions is only 60%-70%; As easily forms volatile hydrides, resulting in a loss rate exceeding 25%. For sparingly soluble elements Al and Cr: The carbon skeleton of carbonized resin can encapsulate elements such as Al and Cr, which cannot be completely disassembled by conventional acid systems (single nitric acid), leaving trace residues after digestion, resulting in a recovery rate below 85%. For alkali metal elements Na and K: The surface of carbonized resin easily adsorbs Na and K from the environment, and trace contamination from acid reagents and containers during digestion can cause fluctuations in blank values, interfering with the accurate detection of low-content samples, with RSDs often exceeding 15%.

[0005] Finally, there is the compatibility of the digestion system: the high carbon content of carbonized resin means that conventional wet digestion requires a large amount of strong acid (≥15mL) and the digestion is incomplete. A single acid system (such as only nitric acid) cannot break the carbon bond, and an improper ratio of mixed acids will cause some elements to precipitate (such as when HF is insufficient, Si and Al form insoluble silicates).

[0006] Currently, the main methods for detecting elemental content in resins include chemical titration, atomic absorption spectrometry (AAS), and inductively coupled plasma optical emission spectrometry (ICP-OES). While chemical titration is simple to operate, its accuracy is relatively low, and it cannot achieve simultaneous detection of multiple elements. AAS, although possessing high sensitivity, has a limited detection range and requires sophisticated sample pretreatment. Inductively coupled plasma optical emission spectrometry (ICP-OES), with its wide linear range, high sensitivity, and ability to simultaneously detect multiple elements, is gradually becoming the mainstream method for elemental detection in resins.

[0007] In sample pretreatment, traditional methods such as wet digestion and dry ashing suffer from problems such as complex operation, incomplete digestion, and high detection limits. In recent years, microwave digestion has been increasingly applied to the pretreatment of resin samples due to its advantages of speed, efficiency, and complete digestion. Microwave digestion directly heats the sample through molecular polarization and ionic conductivity effects, causing the solid sample to break down rapidly and react with the solvent, thereby achieving complete sample digestion.

[0008] Most existing resin pretreatment and detection technologies focus on the determination of single element content. However, with the development of adsorption purification technology, the requirements for resin element content detection are becoming increasingly stringent. Summary of the Invention This invention specifically discloses a method for detecting the elemental content in carbonized resins. By optimizing microwave digestion conditions and ICP-OES detection conditions, a rapid, accurate, and reliable method for detecting elemental content is achieved. This method not only meets the requirement for simultaneous detection of multiple elements in carbonized resins but also has advantages such as simple operation, low detection limit, high precision, and reduced matrix interference. It is expected to be widely used in the field of carbonized resin quality control and performance evaluation.

[0009] This invention addresses the combined problems of "high-carbon matrix interference + loss of volatile elements + encapsulation of sparingly soluble elements" through three operations: nitric acid-hydrofluoric acid mixing ratio, microwave digestion procedure, and the addition of internal standards and stabilizers. Microwave digestion not only shortens digestion time but also reduces reagent usage, thus minimizing environmental pollution. In the instrument detection section, by combining the internal standard method with the standard addition method, matrix interference during detection is reduced, while the internal standard solution ensures instrument stability and accuracy, guaranteeing the accuracy of the obtained data.

[0010] To achieve the aforementioned objectives, the technical solution adopted by this invention is as follows: A method for detecting the elemental content in carbonized resin, comprising the following steps: S1. Sample pretreatment: Take the dried carbonized resin sample into the digestion vessel, add mixed acid, set the microwave digestion program to start digestion, and after digestion is completed, wait for it to cool to room temperature. Dilute the digestion solution with ultrapure water, take 10 mL and add an equal amount of chemical additives and internal standard solution to obtain the sample solution to be tested. S2. Sample Detection: Divide the sample solution into 5 portions, each 10 mL, and add 0, 0.5, 1.0, 3.0, and 5.0 mL of 10 mg / L standard solution of the analyte to each portion. Measure the signal intensity ratio R of the analyte to the internal standard in each solution. Plot a standard curve with the spiked concentration as the x-axis and R as the y-axis. Extrapolate the sample concentration and test the other sample solutions.

[0011] In step S1, the mass of the appropriate amount of dried carbonized resin sample is 0.1-0.2g, accurate to 0.0001g; when the mass of the resin sample in the digestion vessel is 0.1g, the volume of the mixed acid is 8-12mL.

[0012] In step S1, the microwave digester is a TANK eco microwave digester.

[0013] In step S1, the mixed acid used in the microwave digestion process is a mixture of nitric acid and hydrofluoric acid, wherein the volume ratio of nitric acid to hydrofluoric acid is 1-3. The microwave digestion program is segmented heating digestion, with a temperature range of 100-220℃ and a digestion time of 0-2 h.

[0014] In some specific embodiments, the operation is as follows: 0.1-0.2 g of carbonized resin sample is added to a clean PFA digestion vessel; 2-6 mL of high-purity nitric acid and 2-4 mL of high-purity hydrofluoric acid are added to the PFA digestion vessel; the PFA digestion vessel is placed in a microwave digester and digestion is performed according to the microwave digestion program; after digestion, the sample is cooled to room temperature, and an appropriate amount of ultrapure water is added to dilute the solution to obtain the sample solution to be tested. At the same time, a blank control experiment is performed with the same operation as before, without adding any sample, to obtain a blank solution.

[0015] The high-purity nitric acid mentioned is nitric acid with a purity greater than 99% and a mass fraction of 69%. The high-purity hydrofluoric acid mentioned is hydrofluoric acid with a purity greater than 99% and a mass fraction of 39%. Preferably, the elements to be detected in the sample solution include one or more of the following: Li, B, Na, Mg, Al, K, Ca, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, As, Ag, Ba, Hg, Pb, Bi, Cd, In, Tl, and Sr.

[0016] The ICP-OES instrument mentioned is a Perkin Elmer Avio 200 ICP-OES instrument.

[0017] The instrument parameters of the ICP-OES are as follows: operating power 1400W, plasma gas flow rate 12L / min, auxiliary gas flow rate 0.4L / min, and nebulizer flow rate 0.7L / min.

[0018] The internal standard solution is a 1 mg / L mixed solution of Sc, Y, and Re, and the chemical additive is a 0.1% (v / v) lanthanum nitrate solution as a solution ionization buffer.

[0019] Before the sample is injected for testing, a multi-element mixed standard solution is prepared according to the type of element to be tested. The sample solution is divided into 5 portions, each 10 mL, and 0, 0.5, 1.0, 3.0, and 5.0 mL of 10 mg / L multi-element mixed standard solution are added to each portion. Simultaneously, 1 mg / L of internal standard solution is added online to each portion of the solution at a volume ratio of 1:1. The signal intensity ratio R of the analyte to the internal standard in each solution is measured. A standard curve is plotted with the spiked concentration as the abscissa and R as the ordinate, and the sample concentration is calculated by extrapolation.

[0020] The signal intensity values ​​of each element in the blank sample and the sample to be tested are detected, and then substituted into the linear regression equation of each element obtained in step S2 to calculate the concentration of the element in the sample solution, and a spiked recovery test is performed.

[0021] Preferably, all operations S1-S2 are performed in a Class 1000 cleanroom, with the sample weighing operation in S1 being completed in a fume hood.

[0022] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a method for detecting the elemental content in carbonized resin. The method employs microwave digestion of the carbonized resin, requiring minimal reagent volume (0.1g sample added to 8mL of concentrated mixed acid). HF breaks down the carbon skeleton, releasing encapsulated elements, while nitric acid oxidizes organic carbon. The procedure is simple, the digestion effect is significant, and environmental contamination of the sample is minimized. Lanthanum nitrate acts as an ionization buffer to suppress alkali metal ionization interference, stabilizing the elemental state in the digestion solution, allowing direct ICP-OES analysis. During testing, the sample solution is used as a standard solution, and a standard curve is plotted using the standard addition method to reduce matrix interference. An internal standard solution is added to correct for physical interference. The method can simultaneously detect the content of 25 elements, providing accurate and reliable data with high detection efficiency. Detailed Implementation

[0023] The present invention will now be described in detail with reference to specific embodiments and figures. The described embodiments are only some embodiments of the present invention, and not all embodiments.

[0024] The numerical ranges used in this application are approximate values, and therefore may include values ​​outside the range unless otherwise stated. The numerical range includes all values ​​from the lower limit to the upper limit, increasing by one unit, provided that there is at least a two-unit interval between any lower value and any higher value.

[0025] Example 1 In this embodiment, the carbonized resin was pretreated using microwave digestion. The elemental content in the resin was determined using a Perkin Elmer Avio 200 ICP-OES spectrometer. The specific procedures are as follows: S1. Place 0.1000 g of resin sample into a clean PFA digestion vessel; add 6.00 mL of high-purity nitric acid and 2.00 mL of high-purity hydrofluoric acid to the PFA digestion vessel; place the PFA digestion vessel in a microwave digestion apparatus, and follow the digestion procedure shown in Table 1; after cooling to room temperature, open the lid to release the gas in a fume hood, add ultrapure water to dilute the solution to 80 mL, and take 10 mL of the diluted sample solution to add an equal amount of chemical additives and internal standard solution to obtain the test sample solution. Simultaneously, perform a blank experiment without adding any sample, with all other procedures identical, to obtain a blank solution. Table 1 Microwave Digestion Heating Program

[0026] S2. Start the ICP-OES instrument and preheat it. Place the PFA injection tube into a PFA bottle containing 5% (w / w) high-purity nitric acid to initialize its optical performance. The ICP-OES instrument parameters are: operating power 1400W, plasma gas flow rate 12L / min, auxiliary gas flow rate 0.4L / min, and nebulizer flow rate 0.7L / min.

[0027] S3. The characteristic wavelengths of the detectable elements that are not affected by the sample matrix were obtained through screening, as shown in Table 2. Five 10 mL aliquots of the sample solution were taken and 0, 0.5, 1.0, 3.0, and 5.0 mL of 10 mg / L standard solution of the target element were added to each aliquot. The signal intensity ratio R of the target element to the internal standard in each solution was measured. A standard curve was plotted with the spiked concentration as the abscissa and R as the ordinate. The sample concentration was extrapolated and the sample concentration was calculated. Other test sample solutions were injected to detect the content and RSD% of the detectable elements in the resin samples, as shown in Table 3.

[0028] The relative standard deviation (RSD) of the detected elemental content in the five parallel samples was less than 15%, indicating that the method has a low limit of quantitation and good stability, with a pretreatment time of approximately 2 hours. Therefore, the pretreatment method employed can rapidly achieve simultaneous detection of multiple elements, providing accurate results, simple operation, and high testing efficiency.

[0029] Table 2. Characteristic wavelengths of detected elements

[0030] Table 3. Content of detected elements (unit: ppm), RSD%, and spiked recovery rate.

[0031] Example 2 Based on Example 1, the sample was an ion exchange resin, and other conditions remained unchanged. The resin was completely digested, and the digestion solution was clear and yellow. ICP-OES analysis of the test solution and blank solution yielded the elemental content and RSD%, as shown in Table 4. This method is applicable to various types of resins and can be used as a general method for resin digestion testing.

[0032] Table 4. Content of detected elements (unit: ppm), RSD%

[0033] Comparative Example 1 Based on Example 1, the pretreatment method was wet digestion, and the specific conditions were as follows: Add 15.00 mL of high-purity nitric acid and 5.00 mL of high-purity hydrofluoric acid to a PFA digestion vessel containing 0.1000 g of carbonized resin sample; place it on a hot plate and heat at 200 ℃ in a sealed container for 2 h; after the reaction is complete, open the lid, heat the solution at 150 ℃ to concentrate it to 3 mL, add ultrapure water to dilute the solution to 80 mL, and keep other operations unchanged; ICP-OES test the content and RSD% of the detected elements in the test solution and blank solution, as shown in Table 5.

[0034] Wet digestion was used for pretreatment, which took about 3 hours, a relatively long time. When heating with the lid open, elements such as Na, K, and Ca are easily introduced for contamination, resulting in poor data stability. The recovery rates of elements Hg, As, Ga, and Ni were not up to standard due to the open environment. Therefore, wet digestion cannot accurately assess the concentration of these elements in the sample.

[0035] Based on Example 1, with the same sample and reagent amounts, the pretreatment method was wet digestion, heated at 200 °C in a sealed container for 2 hours. Upon opening, the solution was yellowish-brown, with a small amount of yellow gas escaping. A large amount of incompletely digested resin particles were present in the solution. Therefore, microwave digestion saves more time and reagent usage.

[0036] Table 5. Content of detected elements (unit: ppm), RSD%, and spiked recovery rate.

[0037] Comparative Example 2 Based on Example 1, no chemical additives (0.1% lanthanum nitrate solution) were added to the standard solution and the test solution, and other operations remained unchanged. The content and RSD% of the detected elements were obtained by ICP-OES test, as shown in Table 5.

[0038] In parallel samples without chemical additives, the RSD values ​​of elements B, Na, Mg, Al, K, and Ca were greater than 20%, indicating poor sample stability and large fluctuations in element content. Therefore, chemical additives need to be added before testing to stabilize the analytes in the sample and reduce element signal drift.

[0039] Table 6. Content of detected elements (unit: ppm), RSD%

[0040] Comparative Example 3 Based on Example 1, the digestion solution was 8 mL of concentrated nitric acid, and other conditions remained unchanged.

[0041] After the digested sample cooled to room temperature, the lid was opened to release gas. A large amount of yellow gas escaped, and the solution turned dark brown with black suspended particles, indicating incomplete digestion. A second digestion was performed according to the digestion procedure in Table 1, but a small amount of black particles still remained in the resulting digestion solution. Therefore, it is difficult to completely digest the carbonized resin using only nitric acid via microwave.

[0042] Based on Example 1, the digestion solution was 8 mL of concentrated hydrofluoric acid, and other conditions remained unchanged.

[0043] After the digested sample was cooled to room temperature, the lid was opened to release gas. The solution was light brown with some black suspended particles. The resin morphology remained basically unchanged, indicating poor digestion. A second digestion was performed according to the digestion procedure in Table 1. A large number of undigested resin particles still remained in the digestion solution, making it difficult to completely digest the carbonized resin using hydrofluoric acid alone via microwave.

[0044] The above embodiments describe preferred embodiments of the present invention, but the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other way. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention. Therefore, the protection scope of this patent should be determined by the appended claims.

Claims

1. A method for detecting the content of elements in carbonized resin, characterized by, The method comprises the following steps: S1, sample pretreatment: take the dry carbonized resin sample in a digestion tank, add mixed acid, set the microwave digestion program to start digestion, and after digestion is completed, wait for cooling to room temperature, dilute the digestion solution with ultrapure water, take 10 mL, and add an equal amount of chemical additive and internal standard solution to obtain a sample solution to be tested; S2, sample detection: divide the sample solution into 5 parts, and add 0, 0.5, 1.0, 3.0, and 5.0 mL of 10 mg / L of the element standard solution to be tested respectively; measure the signal intensity ratio R of the measured element and the internal standard in each solution; draw a standard curve with the standard concentration as the abscissa and R as the ordinate, and extrapolate to calculate the sample concentration; and sample detection of other sample solutions to be tested.

2. The method for detecting the content of elements in a carbonized resin according to claim 1, characterized by, In the S1 step, the mass of the dry carbonized resin sample is 0.1-0.2 g; and the accuracy is 0.0001 g.

3. The method for detecting the content of elements in a carbonized resin according to claim 1, characterized by, In the S1 step, the ratio of the mass of the resin sample in the digestion tank to the volume of the mixed acid is 0.1: (8-12) g / mL.

4. The method for detecting the content of elements in carbonized resin according to claim 1, characterized by, In the S1 step, the mixed acid used in the microwave digestion process is a mixture of nitric acid and hydrofluoric acid, wherein the volume ratio of nitric acid to hydrofluoric acid is 1-3.

5. The method for detecting the content of elements in carbonized resin according to claim 1, characterized by, In the S1 step, the microwave digestion instrument is a TANK eco microwave digestion instrument.

6. The method for detecting the content of elements in carbonized resin according to claim 1, characterized by, In the S1 step, the microwave digestion program is a segmented temperature program, the temperature is between 100-220℃, the digestion pressure is 1.8-3.0 MPa, and the digestion time is 0-2 h.

7. The method for detecting the content of elements in carbonized resin according to claim 1, characterized by, In the S1 step, the ICP-OES instrument is an inductively coupled plasma emission spectrometer Perkin Elmer Avio 200 ICP-OES.

8. The method for detecting the content of elements in carbonized resin according to claim 1, characterized by, In the S1 step, the instrument parameters of the ICP-OES are: operating power 1200-1600 W, plasma gas flow 10-14 L / min, auxiliary gas flow 0.3-0.5 L / min, and atomizer flow 0.5-0.9 L / min, preferably, operating power 1400 W, plasma gas flow 12 L / min, auxiliary gas flow 0.4 L / min, and atomizer flow 0.7 L / min.

9. The method of claim 1, wherein, In the S1 step, the internal standard solution is a 1 mg / L Sc, Y, Re mixed solution, and the chemical additive is a 0.1% (volume fraction) lanthanum nitrate solution as an ionization buffer.

10. The method for detecting the content of elements in carbonized resin according to claim 1, characterized by, In the S2 step, the sample solution is prepared by the same pretreatment operation; the linear correlation coefficient r² of the standard curve is ≥0.995, and the detected elements include one or more of Li, B, Na, Mg, Al, K, Ca, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, As, Ag, Ba, Hg, Pb, Bi, Cd, In, Tl, and Sr.

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