Method for detecting trace sulfur content in high-purity red phosphorus based on ion chromatography

Abstract

The invention discloses a method for detecting the content of trace sulfur in high-purity red phosphorus based on ion chromatography. The method comprises the following steps: (1) weighing 0.1-0.3 g of high-purity red phosphorus as a sample; (2) adding 2mL of nitric acid into the sample, wherein the nitric acid is electronic-grade nitric acid or high-quality pure nitric acid; (3) taking 2mL of nitric acid as a reagent blank; (4) respectively heating and digesting the sample added with nitric acid and the reagent blank under the same condition; (5) respectively heating the completely digested sample and the reagent blank under the same condition to remove acid; (6) firstly, respectively transferring the sample subjected to thorough acid removal and the reagent blank to a 50mL volumetric flask, and then respectively diluting the sample and the reagent blank with high-purity water to scales; (7) respectively taking the diluted sample and the reagent blank, and determining the content of sulfate ions in the sample and the content of sulfate ions in the reagent blank through ion chromatography; (8) calculating the content S of sulfur in the sample, wherein the content of sulfur in the sample is the content of sulfur in the high-purity red phosphorus; the method is simple, convenient to operate, good in reproducibility and low in cost.

Description

Technical Field

[0001] The invention relates to the technical field of impurity content detection in high-purity red phosphorus, and in particular to a method for detecting trace sulfur content in high-purity red phosphorus based on ion chromatography. Background Art

[0002] High-purity red phosphorus, also known as electronic-grade red phosphorus, is a dopant and diffuser for semiconductors. It is the main raw material for semiconductor black phosphorus, GaP, and InP. At present, the method of producing electronic-grade red phosphorus is basically to directly convert it from high-purity yellow phosphorus. The purity of electronic-grade red phosphorus is required to reach 6N, 7N (99.9999%-99.99999%). Therefore, electronic-grade red phosphorus has very high requirements for the content of various impurities. If the product contains excessive trace impurities such as S, As, heavy metals, etc., it will affect the quality of integrated circuits and high-end semiconductor devices. Therefore, if electronic-grade red phosphorus is to be used in the electronics industry, it is necessary to first conduct an impurity content test to determine whether it is qualified. The patent of the prior art, entitled "Analysis Method of Sulfur Impurities in High-Purity Red Phosphorus" and having the publication number "CN 115219379 A", discloses a method for analyzing sulfur impurities in high-purity red phosphorus, comprising the following steps: S1: firstly pickling the red phosphorus, weighing 200-300 parts of red phosphorus containing organic impurities and 400-500 parts of concentrated sulfuric acid; S2: mixing the 200-300 parts of red phosphorus weighed in step S1 and 400-500 parts of concentrated sulfuric acid, and then starting to stir them vigorously; S3: after clarifying for 50 minutes, waiting until the mixture is cooled to 40°C; S4: waiting until the red phosphorus solidifies, separating sulfuric acid, reheating to 80°C to liquefy phosphorus, and then washing the remaining sulfuric acid with hot water to obtain refined red phosphorus; S5: performing combustion oxidation treatment, and heating in an insulated heating furnace; S6: after cooling, screening and drying the product, sampling and analyzing, and then weighing and calculating the obtained substance to obtain the sulfur content. However, such a method is too complicated, inconvenient to operate and has high cost. Summary of the invention

[0003] In view of this, the purpose of the present invention is to provide a method for detecting trace sulfur content in high-purity red phosphorus based on ion chromatography, so as to solve the technical problems that the existing analysis methods of impurity sulfur in high-purity red phosphorus are too complicated and inconvenient to operate.

[0004] The objective of the present invention is achieved through the following technical solutions:

[0005] A method for detecting trace sulfur content in high-purity red phosphorus based on ion chromatography, comprising the following steps:

[0006] (1) Weigh 0.1-0.3 g of high-purity red phosphorus as a sample;

[0007] (2) Add 2 mL of nitric acid to the sample, the purity of which should be ≥ 65%;

[0008] (3) Take 2 mL of nitric acid as the reagent blank;

[0009] (4) heating and digesting the sample with nitric acid and the reagent blank under the same conditions;

[0010] (5) Heat the completely digested sample and reagent blank to remove the acid under the same conditions;

[0011] (6) First, transfer the completely acid-free sample and reagent blank to a 50 mL volumetric flask, and then dilute to scale with high-purity water;

[0012] (7) taking the diluted sample and the reagent blank respectively and determining the sulfate ion content of the sample and the sulfate ion content of the reagent blank by ion chromatography;

[0013] (8) Calculate the sulfur content S in the sample using the following formula:

[0014]

[0015] Where: C——Sulfate ion content of the sample, unit: mg / L;

[0016] C 空 ——Sulfate ion content of reagent blank, unit: mg / L;

[0017] V is the volume of the solution obtained in step (6), in mL;

[0018] M is the weight of high-purity red phosphorus measured in step (1), in g;

[0019] The sulfur content in the sample is the sulfur content in high-purity red phosphorus.

[0020] Further, the step (7) is specifically as follows:

[0021] First, prepare a plurality of sulfate ion standard solutions with different concentrations, determine the sulfate ion concentration and peak area of ​​each standard solution by ion chromatography, and draw a standard curve. The standard curve equation is as follows:

[0022] Y = ax + b;

[0023] Where:

[0024] x——sulfate ion concentration, unit: mg / L;

[0025] y——peak area, dimensionless;

[0026] a and b – constants, dimensionless;

[0027] Then, the peak area y1 of sulfate ions in the diluted sample and the peak area y1 of sulfate ions in the diluted reagent blank are determined by ion chromatography. 空 , calculate the sulfate ion content c of the sample and the sulfate ion content C of the reagent blank 空 , the formula is as follows:

[0028] C=(y1-b) / a

[0029] C 空 =(y1 空 -b) / a

[0030] Where:

[0031] y1——peak area of ​​sulfate ions in the sample, dimensionless;

[0032] c——the content of sulfate ions in the sample, in mg / L;

[0033] y1 空 ——peak area of ​​sulfate ion in reagent blank, dimensionless;

[0034] C 空 ——Sulfate ion content in the reagent blank, in mg / L.

[0035] Furthermore, step (1) weighs multiple portions of high-purity red phosphorus as multiple samples, and the multiple portions of high-purity red phosphorus are equal in amount. Step (8) also includes: calculating the average sulfur content of the multiple samples, and the average sulfur content of the multiple samples is the sulfur content in the high-purity red phosphorus.

[0036] Furthermore, the sample to which nitric acid is added and the reagent blank in step (4) are respectively placed in a PTFE digestion tank covered with a PTFE lid, each PTFE digestion tank is respectively placed in a metal container with a lid provided with the same, each metal container is placed in a constant temperature drying oven, the temperature of the constant temperature drying oven is controlled at 150° C., and the drying is performed for 1.8-2.2 hours.

[0037] Furthermore, step (5) is specifically as follows: first, the completely digested sample and reagent blank are transferred to 50 mL beakers respectively, and then the beaker containing the sample and the beaker containing the reagent blank are placed on a hot plate and slowly heated. After evaporating until 1 mL of liquid remains in the beaker, the beaker is cooled slightly, and the inner wall of the beaker is rinsed with 10 mL of high-purity water. The heating is continued, and repeated 3 times until 1 mL of liquid remains in the beaker, and the heating is stopped.

[0038] The beneficial effects of the present invention are:

[0039] The present invention discloses a method for detecting trace sulfur content in high-purity red phosphorus based on ion chromatography, which uses nitric acid to oxidize sulfur in the sample high-purity red phosphorus into SO 2-4. Determine the sulfate ion content of the sample by ion chromatography, subtract the blank, and thus obtain the trace sulfur content in high-purity red phosphorus. This method is simple, easy to operate, reproducible and low-cost.

[0040] In order to improve the accuracy of the detection, multiple samples are taken and tested, and the average sulfur content of the multiple samples is calculated. The average sulfur content of the multiple samples is the sulfur content in the high-purity red phosphorus.

[0041] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be further described in detail below with reference to the accompanying drawings, in which:

[0043] Figure 1 It is a standard curve diagram of sulfate ion of 6 different concentrations of the present invention. DETAILED DESCRIPTION

[0044] The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the preferred embodiments are only for illustrating the present invention, rather than for limiting the protection scope of the present invention.

[0045] Embodiment 1

[0046] A method for detecting trace sulfur content in high-purity red phosphorus based on ion chromatography, comprising the following steps:

[0047] (1) Weigh 3 portions of high-purity red phosphorus as 3 samples, namely sample 1, sample 2, and sample 3. The 3 portions of high-purity red phosphorus are all 0.2 g (accurate 0.001). The 3 samples are placed in 3 PTFE digestion tanks respectively;

[0048] (2) Add 2 mL of electronic grade nitric acid to each of the three samples, cover with a PTFE lid, and then insert the three PTFE digestion tanks into the metal containers that come with them. Tighten the lids and label the outer walls of the three metal containers corresponding to sample 1, sample 2, and sample 3, respectively;

[0049] (3) Take 2 mL of electronic grade nitric acid as a reagent blank, place the reagent blank in an empty PTFE digestion tank, cover it with a PTFE lid, then put the PTFE digestion tank into a metal container that comes with it, tighten the lid, and mark the reagent blank on the outer wall of the metal container;

[0050] (4) Place the metal containers labeled with sample 1, sample 2, sample 3, and reagent blank into a constant temperature drying oven, adjust the temperature to 150°C, and heat for about 2 hours until the samples are completely digested;

[0051] (5) Transfer the completely digested samples and reagent blanks to four 50 mL beakers respectively. Label the four beakers corresponding to sample 1, sample 2, sample 3 and reagent blank with sample 1, sample 2, sample 3 and reagent blank respectively. Rinse the inner walls of the four PTFE digestion tanks with an appropriate amount of high-purity water for three times. Transfer the rinse water to the corresponding beakers. Then place the beakers containing the samples and the reagent blank on a hot plate and heat slowly. Evaporate until 1 mL of liquid remains, then cool slightly. Rinse the inner walls of the beakers with 10 mL of high-purity water and continue heating. Repeat this three times. When heating for the third time, the liquid will emit yellow bubbles, which will disappear completely within 15 to 30 seconds. Continue heating until 1 mL of liquid remains in the beaker, then stop heating.

[0052] (6) After the samples and reagent blanks that have been completely acid-free have cooled, wash the inner walls of the four beakers with appropriate amounts of high-purity water, transfer the solutions in the four beakers to four 50 mL centrifuge tubes, dilute to scale with high-purity water, and label the four centrifuge tubes corresponding to sample 1, sample 2, sample 3, and reagent blank, respectively;

[0053] (7) First, prepare 6 sulfate ion standard solutions of different concentrations. The concentration gradient table is shown in Table 1 below:

[0054] Table 1 SO4 2- Standard solution concentration gradient table

[0055] Solution No. ion Standard solution concentration (mg / L) 1 <![CDATA[SO4 2- ]]> 0 2 <![CDATA[SO4 2- ]]> 0.05 3 <![CDATA[SO4 2- ]]> 0.1 4 <![CDATA[SO4 2- ]]> 0.2 5 <![CDATA[SO4 2- ]]> 0.5 6 <![CDATA[SO4 2- ]]> 1.0

[0056] Take the standard solutions numbered 1 to 6 and place them in 2 mL injection vials. Put them into the automatic sampler and measure the concentration and peak area of ​​6 different concentrations of sulfate ion standard solutions on the GPLA-IC1000 ion chromatograph to draw a standard curve (see Figure 1 ), the standard curve equation is as follows:

[0057] Y = 19.328x + 0.219;

[0058] Where:

[0059] x——sulfate ion concentration, unit: mg / L;

[0060] y——peak area, dimensionless;

[0061] The linear correlation coefficient of the standard curve is R2 = 0.999;

[0062] It was found that the sulfate ion can be separated to the maximum extent when the column switching time is 4.5-6.5min, and the separation effect is good;

[0063] Take the samples and reagent blanks from the four centrifuge tubes respectively and put them into four 2 mL injection vials. Label the four injection vials corresponding to sample 1, sample 2, sample 3 and reagent blank as sample 1, sample 2, sample 3 and reagent blank respectively. Put the four injection vials into the automatic sampler and measure the peak area y1 of sulfate ions in the sample and the peak area y1 of sulfate ions in the reagent blank on the GPLA-IC1000 ion chromatograph. 空 , calculate the sulfate ion content c of the sample and the sulfate ion content C of the reagent blank 空 , the formula is as follows:

[0064] C=(y1 -0.219) / 19.328

[0065] C 空 =(y1 空 -0.219) / 19.328

[0066] Where:

[0067] y1——peak area of ​​sulfate ions in the sample, dimensionless;

[0068] c——the content of sulfate ions in the sample, unit: mg / L;

[0069] y1 空 ——peak area of ​​sulfate ion in reagent blank, dimensionless;

[0070] C 空 ——Sulfate ion content in the reagent blank, unit: mg / L;

[0071] (8) Calculate the sulfur content S in the sample using the following formula:

[0072]

[0073] Where: C——Sulfate ion content of the sample, unit: mg / L;

[0074] C 空 ——Sulfate ion content of reagent blank, unit: mg / L;

[0075] V is the volume of the solution obtained in step (6), in mL;

[0076] M is the weight of high-purity red phosphorus measured in step (1), in g;

[0077] The average sulfur content of multiple samples is calculated as (0.075+0.083+0.058) / 3=0.072 mg / kg (ie, 0.072 mg sulfur per 1 kg of red phosphorus). The average sulfur content of multiple samples is the sulfur content in high-purity red phosphorus.

[0078] Table 2 0.2g sample measured data

[0079] Sample name <![CDATA[The content of SO4 2- (mg / kg) in the sample]]> Sulfur content of the sample (mg / kg) Sample 1 0.225 0.075 Sample 2 0.250 0.083 Sample 3 0.175 0.058

[0080] Embodiment 2

[0081] The difference from the first embodiment is that it also includes:

[0082] Repeat steps (1) to (8), except that the high-purity red phosphorus in step (1) is set to 0.3 g. The sulfur content S in the three samples is (see Table 2). The S content in the high-purity red phosphorus is (0.089+0.072+0.083) / 3=0.081 mg / kg (i.e., 0.081 mg sulfur per 1 kg of red phosphorus).

[0083] Table 3 Measured data of 0.3g sample

[0084] Sample name <![CDATA[The content of SO4 in the sample 2- (mg / kg)]]> Sulfur content of the sample (mg / kg) Sample 4 0.267 0.089 Sample 5 0.217 0.072 Sample 6 0.250 0.083

[0085] Electronic grade nitric acid can be replaced by premium pure nitric acid, but the sulfur content in electronic grade nitric acid is much lower than that in premium pure nitric acid, so the use of electronic grade nitric acid makes the test results more accurate.

[0086] The digestion of the present invention is carried out in a closed tetrafluoroethylene digestion tank with a metal container, and of course it can also be carried out in a colorimetric tube with a piston cover. Carrying out the digestion in a closed tetrafluoroethylene digestion tank with a metal container can avoid the loss of sulfur in the sample to generate SO2 and other substances, which will cause large errors in the detection results, and can avoid the risk of unsafe conditions caused by the cover being punched during the oxidation process.

[0087] The constant temperature drying oven heating digestion of the present invention can be replaced by conventional water bath heating digestion, but the constant temperature drying oven heating digestion consumes less acid, reduces the experimental cost, is more environmentally friendly, has a short digestion time, and does not interfere with the element determination after digestion. In addition, the constant temperature drying oven has good airtightness and will not cause the loss of volatile elements.

[0088] The acid-removing method of the present invention can be replaced by a conventional acid-removing method, such as shaking the solution every 3 to 5 minutes under heating conditions to remove nitric acid, and repeating this action until the solution changes from the brown color of the nitric acid solution to colorless and transparent. However, the acid-removing method of the present invention removes acid more thoroughly, making the detection result more accurate and causing no damage to the instrument.

[0089] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the scope of the claims of the present invention.

Claims

1. A method for detecting trace sulfur content in high-purity red phosphorus based on ion chromatography, Features: It includes the following steps: (1) Weigh 0.1-0.3 g of high-purity red phosphorus as a sample; (2) Add 2 mL of nitric acid to the sample, the purity of which should be ≥ 65%; (3) Take 2 mL of nitric acid as the reagent blank; (4) heating and digesting the sample with nitric acid and the reagent blank under the same conditions; (5) Heat the completely digested sample and reagent blank to remove the acid under the same conditions; (6) First, transfer the completely acid-free sample and reagent blank to a 50 mL volumetric flask, and then dilute to scale with high-purity water; (7) taking the diluted sample and the reagent blank respectively and determining the sulfate ion content of the sample and the sulfate ion content of the reagent blank by ion chromatography; (8) Calculate the sulfur content S in the sample using the following formula: Where: C——Sulfate ion content of the sample, unit: mg / L; C 空 ——Sulfate ion content of reagent blank, unit: mg / L; V is the volume of the solution obtained in step (6), in mL; M is the weight of high-purity red phosphorus measured in step (1), in g; The sulfur content in the sample is the sulfur content in high-purity red phosphorus.

2. The method for detecting trace sulfur content in high-purity red phosphorus based on ion chromatography according to claim 1, Features: The step (7) is specifically as follows: First, prepare a plurality of sulfate ion standard solutions with different concentrations, determine the sulfate ion concentration and peak area of ​​each standard solution by ion chromatography, and draw a standard curve. The standard curve equation is as follows: Y = ax + b; Where: x——sulfate ion concentration, unit: mg / L; y——peak area, dimensionless; a and b – constants, dimensionless; Then, the peak area y1 of sulfate ions in the diluted sample and the peak area y1 of sulfate ions in the diluted reagent blank are determined by ion chromatography. 空 , calculate the sulfate ion content c of the sample and the sulfate ion content C of the reagent blank 空 , the formula is as follows: C=(y1-b) / a C 空 =(y1 空 -b) / a Where: y1——peak area of ​​sulfate ions in the sample, dimensionless; c——the content of sulfate ions in the sample, in mg / L; y1 空 ——peak area of ​​sulfate ion in reagent blank, dimensionless; C 空 ——Sulfate ion content in the reagent blank, in mg / L.

3. The method for detecting trace sulfur content in high-purity red phosphorus based on ion chromatography according to claim 1, Features: Step (1) weighs a plurality of portions of high-purity red phosphorus as a plurality of samples, wherein the plurality of portions of high-purity red phosphorus are equal in weight. Step (8) further comprises: calculating an average value of the sulfur content of the plurality of samples, wherein the average value of the sulfur content of the plurality of samples is the sulfur content in the high-purity red phosphorus.

4. The method for detecting trace sulfur content in high-purity red phosphorus based on ion chromatography according to claim 1, Features: The sample and reagent blank added with nitric acid in step (4) are respectively placed in a tetrafluoroethylene digestion tank covered with a tetrafluoroethylene cover, each tetrafluoroethylene digestion tank is respectively placed in a metal container with a cover provided with the same standard, each metal container is placed in a constant temperature drying oven, the temperature of the constant temperature drying oven is controlled at 150° C., and the drying is performed for 1.8-2.2 hours.

5. The method for detecting trace sulfur content in high-purity red phosphorus based on ion chromatography according to any one of claims 1 to 4, Features: Step (5) is specifically as follows: first, transfer the completely digested sample and reagent blank to 50 mL beakers respectively, then place the beaker containing the sample and the beaker containing the reagent blank on a hot plate and slowly heat them. After evaporating until 1 mL of liquid remains in the beaker, cool it slightly, rinse the inner wall of the beaker with 10 mL of high-purity water, continue heating, repeat 3 times, until 1 mL of liquid remains in the beaker, and stop heating.

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