Method for detecting content of trace sulfur in high-purity red phosphorus based on ultraviolet spectrophotometry

Abstract

The invention discloses a method for detecting the content of trace sulfur in high-purity red phosphorus based on ultraviolet spectrophotometry. The method comprises the following steps: (1) weighing the high-purity red phosphorus as a sample; (2) adding 2mL of nitric acid into the sample; (3) taking 2mL of nitric acid as a reagent blank; (4) respectively heating and digesting the sample and the reagent blank under the same condition; (5) respectively heating the sample and the reagent blank for acid removal under the same condition; (6) firstly, respectively diluting the sample subjected to thorough acid removal and the reagent blank to 10mL by using high-purity water, then respectively transferring the diluted sample and the reagent blank to 50mL volumetric flasks, then respectively adding 10mL of a stabilizer and 1mL of a hydrochloric acid solution into each volumetric flask in sequence, then respectively slowly dropwise adding 3mL of a barium chloride solution with the concentration of 250g / L into each volumetric flask, and finally respectively diluting the diluted sample and the diluted reagent blank to scales by using high-purity water, shaking for 1min and standing for 10min; (7) respectively measuring the content of sulfate ions of the sample and the content of sulfate ions of the reagent blank on an ultraviolet and visible spectrophotometer; and (8) calculating the content of sulfur in the high-purity red phosphorus by adopting a formula.

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 ultraviolet spectroscopy. 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. But such method is too complicated and inconvenient to operate. 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 ultraviolet spectroscopy, so as to solve the technical problems that the existing analysis method of impurity sulfur in high-purity red phosphorus is 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 ultraviolet spectroscopy comprises the following steps:

[0006] (1) Weigh 0.1-0.5 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, dilute the completely acid-removed sample and reagent blank to 10 mL with high-purity water, and then transfer them to 50 mL volumetric flasks. Then, add 10 mL of stabilizer and 1 mL of hydrochloric acid solution to each volumetric flask in sequence. Then, slowly add 3 mL of 250 g / L barium chloride solution to each volumetric flask, shake while adding. After the addition is complete, dilute to the scale with high-purity water, shake for 60-70 seconds, and let stand for 9-11 minutes.

[0012] (7) Take the sample and the reagent blank after standing and measure the sulfate ion concentration C of the sample and the sulfate ion concentration C of the reagent blank by UV-visible spectrophotometry. 空 ;

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

[0014]

[0015] Where: C——the concentration of sulfate ions in the sample, unit: mg / L;

[0016] C 空 ——The concentration of sulfate ions in the reagent blank, in 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 sulfate standard solution with a concentration of 0.1 mg / mL;

[0022] Then, take different amounts of sulfate standard solution into 50mL volumetric flasks, add 10mL of stabilizer and 1mL of hydrochloric acid solution to each volumetric flask, and then slowly drop 3mL of 250g / L barium chloride solution into each volumetric flask, shake while dropping, dilute to the scale with high-purity water after the addition is completed, shake for 60-70s, and let stand for 9-11min;

[0023] Then, several portions of the standard solution were taken after standing, and the concentration and absorbance of sulfate ions in the standard solution were determined by UV-visible spectrophotometry at a wavelength of 460 nm, and a standard curve was drawn. The equation of the standard curve is as follows:

[0024] Abs=K1X+K0

[0025] Where:

[0026] Abs - absorbance of sulfate ion, dimensionless;

[0027] X——sulfate ion concentration, unit: mg / L;

[0028] K0 and K1 – constants, dimensionless;

[0029] Finally, the absorbance of sulfate ions in the sample after standing in step (6) and the absorbance of sulfate ions in the reagent blank are measured by UV-visible spectrophotometry, and the concentration of sulfate ions in the sample c and the concentration of sulfate ions in the reagent blank c are calculated. 空 , the calculation formulas are as follows:

[0030] C=(Abs 1-K0) / K1

[0031] C 空 =(Abs 1 空 -K0) / K1

[0032] Where:

[0033] C——The concentration of sulfate ions in the sample, in mg / L;

[0034] Abs 1——absorbance of sulfate ions in the sample, dimensionless;

[0035] C 空 ——The concentration of sulfate ions in the reagent blank, in mg / L;

[0036] Abs 1 空 ——The absorbance of sulfate ions in the reagent blank, dimensionless.

[0037] 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 weight. Step (8) also includes: calculating an average value of the sulfur content of the multiple samples, and the average value of the sulfur content of the multiple samples is the sulfur content in the high-purity red phosphorus.

[0038] Furthermore, the steps (1) to (8) are performed multiple times, and the weights of the high-purity red phosphorus obtained multiple times are not consistent. The method further includes the step of calculating the average sulfur content of all samples obtained multiple times, and the average sulfur content of all samples obtained multiple times is the sulfur content in the high-purity red phosphorus.

[0039] Furthermore, the stabilizer is a polyvinyl alcohol solution with a concentration of 0.5%.

[0040] Furthermore, the sample to which nitric acid is added and the reagent blank in step (4) are respectively placed in a tetrafluoroethylene digestion tank covered with a tetrafluoroethylene lid, each tetrafluoroethylene 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.

[0041] Furthermore, step (5) is specifically as follows: first, the completely digested sample and the 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.

[0042] Furthermore, in the step (6), the barium chloride solution is added dropwise while being kept warm at 50° C., and the keeping warm is continued until the detection is completed on the UV-visible spectrophotometer.

[0043] The beneficial effects of the present invention are:

[0044] The present invention discloses a method for detecting trace sulfur content in high-purity red phosphorus based on ultraviolet spectrometry, 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 UV-visible spectrophotometry, 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.

[0045] 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.

[0046] 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

[0047] 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:

[0048] Figure 1 The figure is a standard curve diagram of 7 different amounts of sulfate standard solutions of the present invention. DETAILED DESCRIPTION

[0049] 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.

[0050] Embodiment 1

[0051] A method for detecting trace sulfur content in high-purity red phosphorus based on ultraviolet spectroscopy comprises the following steps:

[0052] (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;

[0053] (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;

[0054] (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;

[0055] (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;

[0056] (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.

[0057] (6) First, prepare the reagents:

[0058] Preparation of 250g / L barium chloride solution: weigh 62.5g barium chloride, dissolve in high-purity water, transfer to a 250mL volumetric flask, and dilute to the mark;

[0059] Preparation of 0.5% polyvinyl alcohol solution: weigh 5g polyvinyl alcohol into a beaker, add 100mL high-purity water, heat on an electric stove, stir while heating until the polyvinyl alcohol is completely dissolved, transfer to a 1000mL volumetric flask after cooling, rinse the beaker 3 times, transfer to the volumetric flask, and dilute to the scale;

[0060] Preparation of hydrochloric acid solution: Mix 10 mL of hydrochloric acid reagent with 30 mL of high-purity water;

[0061] Then, 1 mL of the liquid in the four beakers finally obtained in step (5) is diluted to 10 mL with high-purity water, and then transferred to four 50 mL volumetric flasks, respectively. The four beakers are rinsed with an appropriate amount of high-purity water for 3 times, and the rinse water is transferred to the corresponding volumetric flasks. Then, 10 mL of stabilizer and 1 mL of hydrochloric acid solution are added to the four volumetric flasks in sequence, and then 3 mL of barium chloride solution with a concentration of 250 g / L is slowly added to the four volumetric flasks. When the barium chloride solution is added, the sample needs to be kept at 50° C. and shaken while adding. Finally, it is diluted to the scale with high-purity water, kept at 50° C. and shaken for 1 min, and kept at 50° C. and allowed to stand for 10 min to completely generate fine barium sulfate particles.

[0062] (7) Preparation of 0.1 mg / mL sulfate standard solution: Accurately weigh 0.148 g of anhydrous sodium sulfate dried to constant weight at 105-110°C, dissolve in high-purity water, transfer to a 1000 mL volumetric flask, and dilute to the mark;

[0063] Take 7 portions of sulfate standard solution into 7 50mL volumetric flasks respectively, the sampling amounts of the 7 portions of sulfate standard solution are 0ml, 1ml, 2ml, 3ml, 4ml, 5ml and 6ml respectively, add 10mL of stabilizer and 1mL of hydrochloric acid solution into the 7 volumetric flasks respectively, then slowly drop 3mL of 250g / L barium chloride solution into the 7 volumetric flasks respectively, shake while dropping, dilute to the scale with high-purity water after the addition is completed, shake for 60-70s, and let stand for 9-11min;

[0064] Take 7 portions of the standard solution after standing to rinse 7 1cm cuvettes 3 times, take 7 portions of the standard solution and place them in the rinsed cuvettes, place the 7 cuvettes in the sample pool of T600S UV-Vis spectrophotometer, measure the absorbance of the 7 standard solutions at 460nm, and draw a standard curve with sulfate concentration as the horizontal axis and the corresponding absorbance as the vertical axis (see Figure 1 ), the standard curve equation is as follows:

[0065] Abs=11.88571X-0.01653

[0066] Where:

[0067] Abs - absorbance of sulfate ion, dimensionless;

[0068] X——sulfate ion concentration, unit: mg / L;

[0069] Take the reagent blank after standing in step (6) and rinse the 1 cm cuvette 3 times, take the reagent blank in the cuvette, take the three samples after standing in step (6) and rinse the three 1 cm cuvettes 3 times respectively, take the three samples and place them in the rinsed cuvettes respectively, place the four cuvettes in the sample cell of T600S UV-visible spectrophotometer, measure the absorbance of the three samples and the absorbance of the reagent blank at 460 nm respectively, and calculate the concentration c of sulfate ions in the samples and the concentration c of sulfate ions in the reagent blank 空 , the calculation formulas are as follows:

[0070] C=(Abs 1+0.01653) / 11.88571

[0071] C 空 =(Abs 1 空 +0.01653) / 11.88571

[0072] Where:

[0073] C——The concentration of sulfate ions in the sample, in mg / L;

[0074] Abs 1——absorbance of sulfate ions in the sample, dimensionless;

[0075] C 空 ——The concentration of sulfate ions in the reagent blank, in mg / L;

[0076] Abs 1 空 ——The absorbance of sulfate ions in the reagent blank, dimensionless.

[0077] The measurement should be completed within 10 minutes on a UV-visible spectrophotometer, and the measurement process should be kept at 50°C;

[0078] (8) The sulfur content S in the three samples was calculated using the following formula (see Table 1):

[0079]

[0080] Where: C——concentration of sulfate ions in the sample, unit: mg / L;

[0081] C 空 ——The concentration of sulfate ions in the reagent blank, in mg / L;

[0082] V is the volume of the solution obtained in step (6), in mL;

[0083] M is the weight of high-purity red phosphorus measured in step (1), in g;

[0084] The average sulfur content of the multiple samples is calculated as (0.050+0.067+0.050) / 3=0.056 mg / kg. The average sulfur content of the multiple samples is the sulfur content in the high-purity red phosphorus.

[0085] Table 1 0.1g sample measured data

[0086]

[0087] Embodiment 2

[0088] The difference from the first embodiment is that it also includes:

[0089] 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 (0.061+0.061+0.056) / 3=0.059 mg / kg (i.e., 0.074 mg sulfur per 1 kg of red phosphorus).

[0090] Table 2 0.3g sample measured data

[0091]

[0092] Repeat steps (1) to (8), except that the high-purity red phosphorus in step (1) is set to 0.5 g. The sulfur content S in the three samples is (see Table 2). The sulfur content in the high-purity red phosphorus is (0.057+0.060+0.053) / 3=0.057 mg / kg.

[0093] Table 3 Measured data of 0.5g sample

[0094]

[0095] 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.

[0096] 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.

[0097] 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.

[0098] 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 drive away 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 application removes acid more thoroughly, making the detection results more accurate and causing no damage to the instrument.

[0099] The temperature is kept at 50°C during the whole process of adding barium chloride solution to the sample and testing on the machine, and constant temperature control is performed, and the sample test is completed within 10 minutes to prevent the generation of a large amount of barium phosphate and make the concentration determination of the target anion more accurate.

[0100] The 0.5% polyvinyl alcohol solution can be replaced by 0.5% of 20% Tween-80.

[0101] 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 ultraviolet spectroscopy, characterized in that: It includes the following steps: (1) Weigh 0.1-0.5 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, dilute the completely acid-removed sample and reagent blank to 10 mL with high-purity water, and then transfer them to 50 mL volumetric flasks. Then, add 10 mL of stabilizer and 1 mL of hydrochloric acid solution to each volumetric flask in sequence. Then, slowly add 3 mL of 250 g / L barium chloride solution to each volumetric flask, shake while adding. After the addition is complete, dilute to the scale with high-purity water, shake for 60-70 seconds, and let stand for 9-11 minutes. (7) Take the sample and the reagent blank after standing and measure the sulfate ion concentration C of the sample and the sulfate ion concentration C of the reagent blank by UV-visible spectrophotometry. 空 ; (8) Calculate the sulfur content S in the sample using the following formula: Where: C——the concentration of sulfate ions in the sample, unit: mg / L; C 空 ——The concentration of sulfate ions in the reagent blank, in 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 ultraviolet spectroscopy according to claim 1, characterized in that: The step (7) is specifically: First, prepare a sulfate standard solution with a concentration of 0.1 mg / mL; Then, take different amounts of sulfate standard solution into 50mL volumetric flasks, add 10mL of stabilizer and 1mL of hydrochloric acid solution to each volumetric flask, and then slowly drop 3mL of 250g / L barium chloride solution into each volumetric flask, shake while dropping, dilute to the scale with high-purity water after the addition is completed, shake for 60-70s, and let stand for 9-11min; Then, several portions of the standard solution were taken after standing, and the concentration and absorbance of sulfate ions in the standard solution were determined by UV-visible spectrophotometry at a wavelength of 460 nm, and a standard curve was drawn. The equation of the standard curve is as follows: Abs=K1X+K0 Where: Abs - absorbance of sulfate ion, dimensionless; X——sulfate ion concentration, unit: mg / L; K0 and K1 – constants, dimensionless; Finally, the absorbance of sulfate ions in the sample after standing in step (6) and the absorbance of sulfate ions in the reagent blank are measured by UV-visible spectrophotometry, and the concentration of sulfate ions in the sample c and the concentration of sulfate ions in the reagent blank c are calculated. 空 , the calculation formulas are as follows: C=(Abs 1-K0) / K1 C 空 =(Abs 1 空 -K0) / K1 Where: C——The concentration of sulfate ions in the sample, in mg / L; Abs 1——absorbance of sulfate ions in the sample, dimensionless; C 空 ——The concentration of sulfate ions in the reagent blank, in mg / L; Abs 1 空 ——The absorbance of sulfate ions in the reagent blank, dimensionless.

3. The method for detecting trace sulfur content in high-purity red phosphorus based on ultraviolet spectroscopy according to claim 1, characterized in that: 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 ultraviolet spectroscopy according to claim 1, characterized in that: The stabilizer is a polyvinyl alcohol solution with a concentration of 0.5%.

5. The method for detecting trace sulfur content in high-purity red phosphorus based on ultraviolet spectroscopy according to claim 1, characterized in that: The sample and reagent blank to which nitric acid is added in step (4) are respectively placed in a tetrafluoroethylene digestion tank covered with a tetrafluoroethylene lid, each tetrafluoroethylene 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.

6. The method for detecting trace sulfur content in high-purity red phosphorus based on ultraviolet spectroscopy according to claim 5, characterized in that: 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.

7. The method for detecting trace sulfur content in high-purity red phosphorus based on ultraviolet spectroscopy according to any one of claims 1 to 6, characterized in that: When the barium chloride solution is added dropwise in step (6), the solution is kept warm at 50° C. and the temperature is kept warm until the detection is completed on the UV-visible spectrophotometer.

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