Method for simultaneously determining contents of diboron trioxide and phosphorus pentoxide in boron phosphate

Abstract

The invention discloses a method for simultaneously determining the contents of diboron trioxide and phosphorus pentoxide in boron phosphate, and belongs to the technical field of analytical testing. According to the method, the sample is digested through microwaves, the diboron trioxide and the phosphorus pentoxide can be measured at the same time through the inductively coupled plasma emission spectrometry, the method is easy to operate, efficient, small in reagent dosage and environmentally friendly, but the content of the diboron trioxide and the content of the phosphorus pentoxide can be accurately measured; therefore, the method for measuring the contents of the diboron trioxide and the phosphorus pentoxide in the boron phosphate by utilizing the microwave digestion-inductively coupled plasma emission spectrometry has very important significance.

Description

Technical Field

[0001] The invention belongs to the field of analysis and testing, and particularly relates to a method for simultaneously determining boron phosphate, boron trioxide and phosphorus pentoxide. Background Art

[0002] Boron phosphate is a widely used inorganic chemical material. Adding boron phosphate to ceramic refractory materials can greatly enhance the strength of ceramic materials. Therefore, the ceramic refractory industry is paying more and more attention to the quality of boron phosphate. Accurate determination methods are of great significance for determining process conditions and ensuring product quality.

[0003] Boron phosphate (BPO 4 ), is a copolymer of low melting point boron oxide and phosphorus oxide, and its chemical properties are stable. If the traditional acid-base titration is used to determine the content of boron oxide in boron phosphate, the test data will be inaccurate due to the presence of a large amount of phosphate in the system. 3 ) 2 Phosphate is separated, and then the content of boron oxide in boron phosphate is determined by potentiometric titration. This method can meet the needs of scientific research and production analysis. However, it is necessary to prepare a variety of reagents, and the analysis and determination process is long, specifically requiring high-temperature melting, sample leaching, precipitation filtration and titration. At present, the content of phosphorus pentoxide in boron phosphate is mainly determined by the quinoline phosphomolybdic acid weight method. Whether it is potentiometric titration or weight method, these classical traditional determination methods all need to measure each oxide separately, and it is impossible to achieve the simultaneous determination of two oxides. At the same time, the operation steps are cumbersome, time-consuming, and the experimental process requires the use of a large amount of organic reagents, which pollutes the environment. The present invention digests the sample by microwave, and adopts inductively coupled plasma emission spectrometry to simultaneously determine boron trioxide and phosphorus pentoxide. The method is simple to operate, efficient, small in reagent dosage, and environmentally friendly, but can accurately determine the content of boron trioxide and phosphorus pentoxide. Therefore, it is of great significance to use microwave digestion-inductively coupled plasma emission spectrometry to determine the content of boron trioxide and phosphorus pentoxide in boron phosphate. Summary of the invention

[0004] In view of the above problems, the present invention provides a method for simultaneously determining the content of boron trioxide and phosphorus pentoxide in boron phosphate. The method of the present invention has the advantages of simple operation, small reagent dosage, environmental friendliness, high accuracy, short test cycle, etc.

[0005] Based on the above purpose, the technical solution adopted by the present invention is as follows:

[0006] A method for simultaneously determining the contents of boron trioxide and phosphorus pentoxide in boron phosphate, specifically comprising the following steps:

[0007] (1) Accurately weigh the sample into a polytetrafluoroethylene digestion tank, add aqua regia, place on a pre-digestion heating device at 100-150°C for 5-15 minutes, remove and cool to room temperature, then transfer to a microwave digestion instrument to digest the sample, cool the digested sample to room temperature, transfer to a volumetric flask, and dilute to scale with pure water to obtain a sample solution to be tested; prepare a sample blank solution together with the sample;

[0008] (2) preparing a series of mixed standard solutions of boron and phosphorus with a concentration range of 0 to 20 mg / L, and firstly preparing a sample blank solution under the premise of determining the working parameters of the inductively coupled plasma atomic emission spectrometer. After the test is completed, the mixed standard solutions of boron and phosphorus with different concentrations are fed into the inductively coupled plasma atomic emission spectrometer by a feed pump to perform scanning tests on the mixed standard solutions respectively, and the optimal analytical spectral lines of the boron element and the phosphorus element are determined. Under the optimal analytical spectral lines of the boron element and the phosphorus element, the emission spectrum intensity of each mixed standard solution is measured, and the working curves of boron and phosphorus are plotted with the mass concentration of boron and phosphorus as the abscissa and the emission spectrum intensity as the ordinate, and the linear regression equations of boron and phosphorus are obtained;

[0009] (3) Sample testing: The sample solution obtained in step (1) is fed into an inductively coupled plasma emission spectrometer using a feed pump. The emission spectrum intensities of boron and phosphorus are obtained under the optimal analytical spectrum of boron and phosphorus. The intensities are substituted into the linear regression equation to obtain the mass concentrations (C) of boron and phosphorus in the sample solution. If the test concentrations of boron and phosphorus exceed 20 mg / L, the sample solution needs to be diluted to make the test concentration within 20 mg / L. The boron trioxide and phosphorus pentoxide contents W in the sample are determined by calculation using formula (1): i :

[0010]

[0011] Where:

[0012] c——The concentration of each element in the tested solution after subtracting the blank test, in micrograms per milliliter (mg / L);

[0013] V——the volume of the measured solution, in milliliters (mL);

[0014] d——dilution ratio of the measured solution;

[0015] k——The coefficient of each element converted into oxide, see Table 2 for details;

[0016] m – the value of the sample mass weighed, in grams (g).

[0017] Furthermore, in step (1), 10 mL to 15 mL of aqua regia is added for every 0.15 g of sample.

[0018] Furthermore, in step (1), the microwave digestion procedure is as follows: the first stage: heating from room temperature to 100°C for 10 minutes and maintaining at 100°C for 10 minutes; the second stage: heating from 100°C to 180°C for 10 minutes and maintaining at 180°C for 20 minutes; the third stage: heating from 180°C to 220°C for 10 minutes and maintaining at 220°C for 15 minutes; the sample is taken out after cooling to 80°C for 10 minutes.

[0019] Furthermore, in step (2), the operating parameters of the inductively coupled plasma emission spectrometer are: power of 1150 W, plasma gas flow rate of 16.5 L / min, auxiliary gas flow rate of 2.25 L / min, nebulizer flow rate of 0.75 L / min, injection pump speed of 15 rpm, and injection flushing time of 30 s.

[0020] Furthermore, in step (2), in the mixed standard solution of boron and phosphorus, the mass concentrations of boron and phosphorus are 0.00 mg / L, 1.00 mg / L, 2.00 mg / L, 5.00 mg / L, 10.00 mg / L, and 20.00 mg / L, respectively.

[0021] Among them, the linear regression equation of the boron standard curve is y=3181.4x+383.68, and the linear regression equation of the phosphorus standard curve is y=108.84x+11.186.

[0022] Furthermore, in step (3), 2% to 5% by volume of dilute nitric acid is used to dilute the sample solution.

[0023] Specifically, in step (2), a series of mixed standard solutions of boron and phosphorus with different concentrations are prepared; after the instrument is turned on and stabilized, the polychromator is turned on for high blowing, the interface is purged, and after the wavelength correction is passed, the mixed standard solutions are measured. The mixed standard solutions of boron and phosphorus with different concentrations are fed into the inductively coupled plasma emission spectrometer by a feed pump, and the spectrum intensity count values ​​of each standard solution are measured at the same time, and a working curve is drawn according to the emission spectrum intensity count values. Boron trioxide and phosphorus pentoxide are the main contents in boron phosphate. The corresponding boron and phosphorus elements can simultaneously select multiple characteristic spectral lines as analysis spectral lines. The present invention is screened from the aspects of emission intensity, relative error of standard solution, interference between elements, stability, detection limit, etc., and the spectrum lines with high emission intensity, small relative error of standard solution, small interference of coexisting elements, good stability and low detection limit are selected as the best analysis spectral lines. The best analysis spectral lines of boron and phosphorus elements are shown in Table 1.

[0024] Table 1 Best analysis lines for boron and phosphorus

[0025] element Analytical line / nm B 249.772 P 213.618

[0026] Table 2 Conversion coefficients of each element into oxides

[0027] Element-Oxide Conversion coefficient k <![CDATA[B-B 2 THE 3 ]]> 3.2199 <![CDATA[P-P 2 THE 5 ]]> 2.2914

[0028] The invention can simultaneously determine the contents of boron trioxide and phosphorus pentoxide in boron phosphate, has a simple method, high sensitivity, low detection limit, and accurate and reliable detection results. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a linear relationship graph between mass concentration of B and light intensity;

[0030] Figure 2 There is a linear relationship between P mass concentration and intensity. DETAILED DESCRIPTION

[0031] The following is a complete and detailed description of the present invention in conjunction with specific embodiments, but the present invention is not limited to the following embodiments.

[0032] The materials and reagents used in the examples of the present invention are commercially available products unless otherwise specified. Only reagents and ultrapure water of confirmed high purity or above were used in the analysis.

[0033] Preparation of 5v% dilute nitric acid: Mix 5mL of commercially available concentrated nitric acid and 95mL of ultrapure water.

[0034] The working parameters of the inductively coupled plasma emission spectrometer in the present invention are: power of 1150W, plasma gas flow rate of 16.5L / min, auxiliary gas flow rate of 2.25L / min, nebulizer flow rate of 0.75L / min, injection pump speed of 15rpm, and injection flushing time of 30s.

[0035] Embodiment 1:

[0036] (1) Weigh 0.1500 g of the boron phosphate to be tested provided by a manufacturer as a sample into a polytetrafluoroethylene digestion tank, add 12 mL of hydrochloric acid-nitric acid aqueous solution, place on a pre-digestion heating device to react for 10 min, cool and transfer to a microwave digestion instrument, and digest the sample according to the procedure in Table 3. After digestion, take out the sample, cool the digested sample to room temperature, transfer it to a 250 mL boron-free glass volumetric flask, and dilute to the mark with pure water.

[0037] Prepare a sample blank solution along with the sample: the same as step (1) except that 0.1500 g of boron phosphate sample to be tested is not added.

[0038] Table 3 Microwave digestion procedure

[0039]

[0040] (2) Drawing of working curve: Pipette 0.00mL, 1.00mL, 2.00mL, 5.00mL, 10.00mL, and 20.00mL of 100μg / mL boron standard solution and 100μg / mL phosphorus standard solution into a 100mL volumetric flask, and dilute to scale with 5v% dilute nitric acid. The 100μg / mL boron standard solution and the 100μg / mL phosphorus standard solution are both commercially available standard solutions, the certificate number of the 100μg / mL boron standard solution is NCS148428, and the certificate number of the 100μg / mL phosphorus standard solution is NCS180057. The mass concentrations of boron and phosphorus in the above 100mL volumetric flasks are 0.00mg / L, 1.00mg / L, 2.00mg / L, 5.00mg / L, 10.00mg / L, and 20.00mg / L, respectively, and a series of mixed standard solutions of boron and phosphorus with different concentrations are prepared; 99.999% argon is used as a carrier gas, and a sample blank solution is first introduced. After the test is completed, the mixed standard solutions of boron and phosphorus with different concentrations are fed into the inductively coupled plasma emission spectrometer with a feed pump, and the emission intensity, relative error of the standard solution, interference between elements, stability, detection limit, etc. are screened, and the spectrum with high emission intensity, small relative error of the standard solution, small interference of coexisting elements, good stability, and low detection limit is selected as the best analysis spectrum. First, according to the instrument (small interference of coexisting elements and good stability), the two analysis spectra of boron and phosphorus elements in Tables 4 and 5 are recommended, and then the best analysis spectra of boron and phosphorus elements are screened according to the spectrum line intensity and relative error, as shown in Table 6. Under the optimal analytical spectral lines of boron and phosphorus elements, the emission spectrum intensity of each mixed standard solution was measured.

[0041] Table 4 Test results of boron standard solution at different wavelengths

[0042]

[0043] Table 5 Test results of phosphorus standard solution at different wavelengths

[0044]

[0045] Table 6 Best analysis lines for boron and phosphorus

[0046] element Analytical line / nm B 249.772 P 213.618

[0047] The working curves of boron and phosphorus are plotted with the mass concentration of boron and phosphorus as the ordinate and the emission spectrum intensity as the ordinate. The results are as follows: Figure 1 and Figure 2 According to the working curve, the linear regression equation of the boron standard curve is y = 3181.4x +

[0048] 383.68, the linear correlation coefficient is 0.9992, and the relative error of each standard solution is less than 4%, indicating that the standard curve has strong reliability; the linear regression equation of the phosphorus standard curve is y=108.84x+11.186, the linear correlation coefficient is 0.9999, and the relative error of each standard solution is less than 4%, indicating that the standard curve has strong reliability.

[0049] (3) The solution to be tested in step (1) is fed into an inductively coupled plasma emission spectrometer by a feed pump, and the emission spectrum intensities of boron and phosphorus are simultaneously measured under the optimal analytical spectrum lines of boron and phosphorus. The obtained emission spectrum intensity values ​​are substituted into a linear regression equation to calculate the mass concentrations (C) of boron and phosphorus in the sample solution to be tested. Formula (1) is used to calculate and determine the content W of boron trioxide and phosphorus pentoxide in the sample. i If the test concentration of boron and phosphorus exceeds 20.00 mg / L, it is necessary to dilute it with 5% dilute nitric acid at a certain ratio and then test it so that the concentration of the diluted solution is within 20.00 mg / L.

[0050] The boron trioxide and phosphorus pentoxide content W in the sample is calculated by formula (1): i :

[0051]

[0052] Where:

[0053] c——The concentration of each element in the tested solution after subtracting the blank test, in micrograms per milliliter (mg / L);

[0054] V——the volume of the measured solution, in milliliters (mL);

[0055] d——dilution ratio of the measured solution;

[0056] k——The coefficient of each element converted into oxide, see Table 2 for details;

[0057] m——the value of the sample mass, in grams (g);

[0058] (4) Determination of the detection limit of this example

[0059] The blank solution was measured 10 times continuously, and 3 times the standard deviation of the 10 measurement results was taken as the detection limit, and 5 times the detection limit was taken as the lower limit of determination of this method. The detection limit and lower limit of determination of boron trioxide and phosphorus pentoxide are shown in Table 7.

[0060] Table 7 Detection limit and determination lower limit

[0061]

[0062] (5) Precision test

[0063] Using the sample to be tested in step (1), according to the detection method of the present invention, 6 parallel results were measured, and the test results were processed according to formula (1), m = 0.15g, V = 250mL, and the relative standard deviation of the parallel results was evaluated. The precision results of the detection method are shown in Table 8. The relative standard deviations (RSDs) of boron trioxide and phosphorus pentoxide were 0.087% and 0.045% respectively.

[0064] Table 8 Precision determination results (n = 6)

[0065]

[0066]

[0067] It can be seen from Table 8 that the relative standard deviation of the determination result is less than 1%, indicating that the present invention has good precision and stability in determining the content of boron trioxide and phosphorus pentoxide in boron phosphate. It meets the technical index requirements of the production enterprise for the content of boron trioxide (31.0% to 34.0%) and phosphorus pentoxide (62.0% to 66.0%) in boron phosphate.

[0068] (6) Spike recovery test

[0069] To verify the accuracy of the method, the sample addition recovery test was carried out according to the experimental method provided by the present invention, and the addition recovery was calculated. Addition recovery = (total amount measured - measured value) ÷ amount added × 100%. The measurement results are shown in Table 9. In Table 9, the recovery test was carried out by adding appropriate amounts of boron and phosphorus standard solutions with the mass concentrations of the measured boron and phosphorus elements. The addition recovery of the embodiment was between 96% and 105%, with high recovery and high accuracy of the results.

[0070] Table 9 Spiked recovery determination results

[0071]

[0072] It can be seen that the method of the present invention is simple, has high sensitivity, low detection limit, and accurate and reliable detection results.

Claims

1. A method for simultaneously determining the contents of boron trioxide and phosphorus pentoxide in boron phosphate, characterized in that: The specific steps include: (1) Accurately weigh the sample into a polytetrafluoroethylene digestion tank, add aqua regia, place on a pre-digestion heating device at 100-150°C for 5-15 minutes, remove and cool to room temperature, then transfer to a microwave digestion instrument to digest the sample. After cooling the digested sample to room temperature, transfer it to a volumetric flask and dilute to the mark with pure water to obtain the sample solution to be tested; prepare a sample blank solution together with the sample; (2) Prepare a series of mixed standard solutions of boron and phosphorus with a concentration range of 0-20 mg / L. On the premise of determining the working parameters of the inductively coupled plasma atomic emission spectrometer, first prepare a sample blank solution. After the test is completed, use a feed pump to feed the mixed standard solutions of boron and phosphorus with different concentrations into the inductively coupled plasma atomic emission spectrometer to perform scanning tests on the mixed standard solutions respectively, determine the optimal analytical spectral lines of boron and phosphorus, and measure the emission spectrum intensity of each mixed standard solution under the optimal analytical spectral lines of boron and phosphorus. Draw the working curves of boron and phosphorus with the mass concentration of boron and phosphorus as the horizontal axis and the emission spectrum intensity as the vertical axis to obtain the linear regression equations of boron and phosphorus. (3) Sample testing: The sample solution obtained in step (1) is fed into an inductively coupled plasma emission spectrometer using a feed pump. The emission spectrum intensities of boron and phosphorus are obtained under the optimal analytical spectral lines of boron and phosphorus. The intensities are substituted into the linear regression equation to obtain the mass concentrations of boron and phosphorus in the sample solution (c). If the test concentrations of boron and phosphorus exceed 20 mg / L, the sample solution needs to be diluted to make the test concentration within 20 mg / L. The boron trioxide and phosphorus pentoxide contents W in the sample are determined by calculation using formula (1). i : Where: c ——The concentration of each element in the tested solution after deducting the blank test, in micrograms per milliliter (mg / L); V ——The volume of the measured solution, in milliliters (mL); d ——Dilution ratio of the solution being tested; k ——The conversion coefficient of each element into oxide; m ——The value of the sample mass weighed, in grams (g).

2. The method for simultaneously determining the contents of boron trioxide and phosphorus pentoxide in boron phosphate according to claim 1, characterized in that: In step (1), 10 mL to 15 mL of aqua regia is added for every 0.15 g of sample.

3. The method for simultaneously determining the contents of boron trioxide and phosphorus pentoxide in boron phosphate according to claim 1, characterized in that: In step (1), the microwave digestion procedure is as follows: the first stage: heating from room temperature to 100 °C for 10 min and maintaining at 100 °C for 10 min; the second stage: heating from 100 °C to 180 °C for 10 min and maintaining at 180 °C for 20 min; the third stage: heating from 180 °C to 220 °C for 10 min and maintaining at 220 °C for 15 min; cooling to 80 °C for 10 min and then taking out the sample.

4. The method for simultaneously determining the contents of boron trioxide and phosphorus pentoxide in boron phosphate according to claim 1, characterized in that: In step (2), the operating parameters of the inductively coupled plasma emission spectrometer are: power of 1150 W, plasma gas flow rate of 16.5 L / min, auxiliary gas flow rate of 2.25 L / min, nebulizer flow rate of 0.75 L / min, injection pump speed of 15 rpm, and injection flushing time of 30 s.

5. The method for simultaneously determining the contents of boron trioxide and phosphorus pentoxide in boron phosphate according to claim 1, characterized in that: In step (2), in the mixed standard solution of boron and phosphorus, the mass concentrations of boron and phosphorus are 0.00 mg / L, 1.00 mg / L, 2.00 mg / L, 5.00 mg / L, 10.00 mg / L, and 20.00 mg / L, respectively.

6. The method for simultaneously determining the contents of boron trioxide and phosphorus pentoxide in boron phosphate according to claim 1, characterized in that: In step (2) and step (3), during the test, the best analytical spectra of boron and phosphorus are as follows: 。 7. The method for simultaneously determining the contents of boron trioxide and phosphorus pentoxide in boron phosphate according to claim 1, characterized in that: The linear regression equation for the boron standard curve is y = 3181.4x + 383.68, and the linear regression equation for the phosphorus standard curve is y = 108.84x + 11.

186.

8. The method for simultaneously determining the contents of boron trioxide and phosphorus pentoxide in boron phosphate according to claim 1, characterized in that: In step (3), 2% to 5% dilute nitric acid is used to dilute the sample solution.

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