A method for detecting the reagent concentration of methylene blue solution used in the MB value test of manufactured sand and correcting the MB value result

Abstract

The present invention discloses a method for testing the concentration of methylene blue solution reagent for detecting the MB value of manufactured sand and correcting the MB value result, comprising the following steps: preparation of drugs; preparation of methylene blue solution with a nominal concentration of 10 g / L; determination of the absorbance of the solution. The technical solution of the present invention can effectively control the quality of methylene blue reagent solution for MB value detection. By monitoring the concentration of the prepared solution, it can effectively prevent test errors caused by insufficient purity of the original drug reagent or improper preparation resulting in too low or too high concentration. The technical solution of the present invention can quickly determine whether the prepared methylene blue solution meets the usage requirements. By comparing the absorbance of the dilution (1.5 mg / L) of the prepared methylene blue solution with the absorbance of high-purity copper sulfate pentahydrate reagent at 2.8 g / L, it can quickly determine whether the prepared solution reaches the prepared concentration.

Description

Technical Field

[0001] The present invention relates to the technical field of material property detection, and particularly relates to a method for correcting the reagent concentration and MB value result of methylene blue solution for testing the MB value of manufactured sand. Background Art

[0002] The methylene blue value in manufactured sand is an index used to determine whether the particles with a particle size less than 0.075 mm in manufactured sand are mainly clay or stone powder with the same chemical composition as the processed parent rock. The determination of the methylene blue value mainly utilizes the different adsorption characteristics of methylene blue for stone powder and clay in manufactured sand. The adsorption amount of stone powder for methylene blue is relatively small, while clay has a strong adsorption for methylene blue. By adding methylene blue solution to manufactured sand, and then observing the color change of the solution and the consumed amount of methylene blue to judge the content of clay in manufactured sand.

[0003] In the current national standard GB / T14684-2022 "Sand for construction", it is stipulated that the purity of methylene blue (C 16 H 18 N 3 S·Cl·3H 2 O) is greater than 98.5%, and there are relatively high requirements for the reagent. After investigation, it is found that although the labels of most reagents on the market meet the requirements, the actual purity cannot reach the requirements, and the specification does not stipulate the means to control the quality of the reagent; the concentration of the prepared methylene blue reagent is not calibrated and quality controlled, and it is impossible to determine whether the prepared solution reaches the specified concentration, which in turn affects the MB value result; the MB value result correction is not involved.

[0004] In the standard JGJ52-2006 "Standard for quality and inspection method of sand for ordinary concrete", the purity requirement of methylene blue is not stipulated. After investigation, it is found that most reagents on the market cannot reach the purity requirement, and the specification does not stipulate the means to control the quality of the reagent; the concentration of the prepared methylene blue reagent is not calibrated and quality controlled, and it is impossible to determine whether the prepared solution reaches the specified concentration, which in turn affects the MB value result; furthermore, the MB value result correction is not involved.

[0005] If the purity of the methylene blue reagent is not controlled, it will have a significant impact on the MB value test result, and further affect the performance of concrete. Neither the above-mentioned national specification nor the industry specification mentions calibrating the concentration of the prepared methylene blue, and it is impossible to determine whether the prepared solution reaches the specified concentration.

[0006] Although there are relevant calibration methods for the concentration of methylene blue reagent in "Test Methods for Wood Activated Carbon - Methylene Blue Adsorption Value" GB / T 12496.10 and "Test Methods for Coal-based Granular Activated Carbon - Determination of Methylene Blue Adsorption Value" GB / T 7702.6, the purity calibration method of methylene blue reagent is not specified. Moreover, the required concentration for methylene blue calibration is different from the concentration of the methylene blue solution used for the MB value detection of manufactured sand, and the preparation methods are also different, so it may not necessarily be applicable to the accuracy detection of the MB value of manufactured sand. GB / T 12496.10 also proposes a method for calibrating the methylene blue solution by absorbance, which is also involved in GB / T 7702.6-2008. However, it is old and may not necessarily be applicable to the calibration of the methylene blue reagent solution for the MB test of manufactured sand. The "Chinese Pharmacopoeia" 2020 edition has a content test method for methylene blue (C 16 H 18 CIN 3 S·Cl), but the scope of application may not necessarily be related to the MB value test of manufactured sand.

[0007] In non-building material fields, the used fields are different and there are applicable preconditions: the content of methylene blue indicator used in the preparation of methylene blue test solution is above 98.5%, and it needs to be prepared strictly in accordance with Article 5.5.1 of GB / T 12496.10, and the calibrated concentration is 1.5 g / L; the technical index of the concentration of anhydrous copper sulfate in the spectrophotometer method of Article 8.3 has been reconfirmed with pure water as the diluent due to its old age and different diluents.

[0008] In view of the above technical problems, it is an urgent technical problem to propose a method for testing the concentration of methylene blue solution reagent for MB value detection of manufactured sand and correcting the MB value results. Summary of the Invention

[0009] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a method for testing the concentration of methylene blue solution reagent for MB value detection of manufactured sand and correcting the MB value results, which can not only quickly test the concentration of the prepared methylene blue solution, reduce the consumption of samples and methylene blue solution, but also quickly determine the purity of the original methylene blue drug, improve the accuracy of the MB value of manufactured sand and reduce errors, making up for the deficiencies of standards and the industry.

[0010] Aiming at the deficiencies of the prior art, the present invention provides a method for testing the concentration of methylene blue solution reagent for MB value detection of manufactured sand and correcting the MB value results, including the following steps:

[0011] Step S1, drug preparation: Select methylene blue chemical drugs with a labeled purity ≥ 82% (hereinafter all calculated as C 16 H 18 N 3 S·Cl·3H 2 O).

[0012] Step S2, preparation of solution: Prepare a methylene blue solution with a nominal concentration of 10 g / L.

[0013] Step S3, determination of absorbance of solution: Pipette 30 ml of the methylene blue solution with a nominal concentration of 10 g / L into a 200 ml volumetric flask and dilute it with pure water to prepare a methylene blue reagent solution with a nominal concentration of 1.5 g / L; Pipette 10 mL of the 1.5 g / L methylene blue solution into a 200 mL volumetric flask again, dilute it to the mark with pure water, and shake well; Then accurately pipette 20 mL from this diluted solution into a 1000 mL volumetric flask and dilute it to the mark with pure water, shake well to prepare a 1.5 mg / L reagent solution, and measure the absorbance with a spectrophotometer; Prepare a reference solution with a concentration of 2.80 g / 100 mL using a high-purity reagent or primary standard reagent of copper sulfate pentahydrate with a purity above 99.9%, and measure its absorbance at a wavelength of 665 nm and a light path of 1 cm. All tests use pure water as a reference; If the difference in absorbance between the reagent solution and the reference solution is within ±0.020, the prepared methylene blue solution with a concentration of 10 g / L can be directly used for the MB value test, and the MB value result does not need to be corrected; If the difference in absorbance between the reagent solution and the reference solution is greater than ±0.020, MB value detection and correction are required.

[0014] Further, the MB value detection and correction include the following steps:

[0015] (1) Calibration of the concentration of the methylene blue solution and calculation of purity: Use the methylene blue solution with a nominal concentration of 10 g / L prepared in Step S2 to perform calibration and calculate the drug purity according to the improved iodometric method.

[0016] (2) MB value detection and correction.

[0017] Further, the calibration of the concentration of the methylene blue solution in step (1) is carried out according to the improved iodometric method, and the specific steps are as follows:

[0018] Pipette 30 mL of the methylene blue solution with a nominal concentration of 10 g / L prepared in Step S2 into a 200 mL volumetric flask and dilute it to prepare a methylene blue test solution with a nominal concentration of 1.5 g / L. Pipette 50 mL of the test solution into a 250 mL brown volumetric flask, add 25 mL of 36% acetic acid and shake well, add 30 mL of 0.1 mol / L iodine standard solution, shake for 1 min, place the brown volumetric flask in the dark for 1 h, shake it every 10 min during this period, dilute it to the mark with water, shake well, filter it with filter paper, discard the first 20 mL of the solution, and collect the subsequent filtrate in a dry Erlenmeyer flask; Pipette 100 mL of the above filtrate, titrate it with 0.1 mol / L sodium thiosulfate solution until it turns light yellow, and continue titrating with starch solution as an indicator until it becomes colorless as the end point.

[0019] Take another 50 mL of pure water and place it in a 250 mL brown volumetric flask for a blank test;

[0020] The concentration of the methylene blue solution is calculated according to formula (a), and the calibration result is recorded as the calibration value C, with the unit g / L.

[0021] Concentration of methylene blue solution:

[0022] C = C 0 (V 1 - V) × 3.196 (a)

[0023] In the formula: C 0 — Concentration of sodium thiosulfate, mol / L;

[0024] V — Volume of sodium thiosulfate solution consumed in the blank test, mL;

[0025] V 1 — Volume of sodium thiosulfate solution consumed by the reagent, mL;

[0026] 319.6 — Molar mass of methylene blue (C 16 H 18 N 3 S·Cl), g / mol.

[0027] Furthermore, the measured value C 1 of the concentration of the methylene blue solution with a nominal concentration of 10 g / L prepared in step (1), in the unit g / L, is calculated according to formula (b):

[0028]

[0029] where C is the calibrated concentration of the methylene blue solution according to step (1).

[0030] Furthermore, the calculation of the purity of the methylene blue solution in step (1) is carried out according to the following steps:

[0031]

[0032]

[0033] where C 1 is the measured value of the concentration of the methylene blue solution with a nominal concentration of 10 g / L prepared (unit g / L), m represents the mass of the drug weighed, in the unit g, and the content (Ma, unit %) of methylene blue anhydrous (C 16 H 18 N 3 S·Cl) is calculated according to formula (c), and the drug purity of methylene blue trihydrate (C 16 H 18 N 3 S·Cl·3H 2O)(M c , in units of %, is calculated according to formula (d).

[0034] Furthermore, in step (2), the MB value detection uses the prepared methylene blue solution with a nominal concentration of 10 g / L for the MB value test.

[0035] Furthermore, in step (2), the MB value correction is calculated according to formula (e) in combination with the calibrated value C of the concentration of the methylene blue solution in step (1), and the MB value correction coefficient is

[0036]

[0037] Compared with the prior art, the present invention has the following advantages:

[0038] 1) The technical solution of the present invention can effectively control the quality of the methylene blue reagent solution for MB value detection. By monitoring the concentration of the prepared solution, it can effectively prevent test errors caused by insufficient purity of the original drug reagent or improper preparation resulting in too low or too high concentration.

[0039] 2) The technical solution of the present invention can quickly determine whether the prepared methylene blue solution meets the usage requirements. By measuring the absorbance of the dilution (1.5 mg / L) of the prepared methylene blue solution and comparing it with the absorbance of the high-purity copper sulfate pentahydrate reagent of 2.8 g / L, it can quickly determine whether the prepared solution reaches the prepared concentration.

[0040] 3) The technical solution of the present invention can quickly determine whether the purity of the original methylene blue reagent can meet the requirements. If the preparation process is correct and there is no obvious operation error, by calibrating the concentration of the prepared solution and calculating the purity of the drug, it can be determined whether the original drug reagent meets the required purity.

[0041] 4) The technical solution of the present invention can quickly and accurately test the MB value. By measuring the concentration of the prepared methylene blue solution and correcting the MB value according to the measured concentration value, the correct value of the MB value can be found more accurately and quickly without re-preparing the solution and replacing with better drugs. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 is the label diagram of samples No. 1-9 in Example 1;

[0043] Figure 2 is the schematic diagram of the method flow in Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0044] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0045] Embodiment 1:

[0046] There are two main types of methylene blue on the market: methylene blue anhydrate, molecular formula C 16 H 18 N 3 S·Cl; Methylene blue trihydrate, molecular formula C 16 H 18 N 3 S·Cl·3H 2 O. This example uses 9 kinds of methylene blue reagents produced by different manufacturers. The information of the reagent labels, purity and composition, etc. are shown in Table 1. The labels of samples No. 1-9 are as follows: Figure 1 shown.

[0047] Artificial sand: Artificial sand produced by Chongqing Tonglei Building Materials Co., Ltd. Absorbance reference reagent: Copper sulfate pentahydrate produced by Aladdin, 99.99% metals basis; the test water is pure water.

[0048] The method for correcting the concentration of methylene blue solution reagent and the MB value result for testing the MB value of machine-made sand provided in this embodiment comprises the following steps:

[0049] Step S1: Drug preparation: Select drugs from regular sources, produced by chemical manufacturers with a label purity of ≥82% (in C 16 H 18 N 3 S·Cl·3H 2 The high-quality chemicals (measured by weight) are shown in Table 1. Since the purity of label No. 1 is qualified, sample No. 1 is used as a control example;

[0050] Table 1 Specifications of methylene blue from different manufacturers

[0051]

[0052] Step S2: Preparation of solution: According to the preparation method of methylene blue solution in national standard GB / T 14684-2022, the methylene blue reagent in Table 1 is prepared into a methylene blue solution with a nominal concentration of 10 g / L;

[0053] Step S3: Measurement of the absorbance of the solution: Pipette 30 mL of the methylene blue solution with a nominal concentration of 10 g / L into a 200 mL volumetric flask and dilute it with pure water to prepare a methylene blue reagent solution with a nominal concentration of 1.5 g / L; Pipette 10 mL of the 1.5 g / L methylene blue solution again into a 200 mL volumetric flask, dilute it to the mark with pure water, and shake well; Then accurately pipette 20 mL from this diluted solution into a 1000 mL volumetric flask and dilute it to the mark with pure water, shake well to prepare a reagent solution of 1.5 mg / L, and measure the absorbance with a spectrophotometer; Prepare a reference solution with a concentration of 2.80 g / 100 mL using a high-purity reagent or primary standard reagent of copper sulfate pentahydrate with a purity of more than 99.9%, and measure its absorbance at a wavelength of 665 nm and a light path of 1 cm. All tests are referenced with pure water. The test results are shown in Table 2.

[0054] Table 2 Test Results of Methylene Blue Absorbance

[0055]

[0056] Since the difference between the absorbances of No. 3 and No. 7 and that of the reference solution does not exceed ±0.020, directly measure the methylene blue solution with a nominal concentration of 10 g / L prepared according to the determination method of the methylene blue value of manufactured sand specified in GB / T 14684-2022. The measurement results are: the MB value of No. 3 is 0.5, and the MB value of No. 7 is 0.5.

[0057] Step S4: Calibration of the solution concentration and calculation of the drug purity: Use the methylene blue solution with a nominal concentration of 10 g / L prepared above to carry out calibration and drug purity calculation according to the improved iodometric method. The specific steps are as follows:

[0058] (1) Calibration of the solution concentration:

[0059] Pipette 30 ml of the methylene blue solution with a nominal concentration of 10 g / L prepared in Step S2 into a 200 ml volumetric flask and dilute it to prepare a methylene blue test solution with a nominal concentration of 1.5 g / L. Pipette 50 mL of the test solution into a 250 mL brown volumetric flask, add 25 mL of 36% acetic acid and shake well, add 30 mL of 0.1 mol / L iodine standard solution, shake for 1 min, place the brown volumetric flask in the dark for 1 h, shake it once every 10 min during this period, dilute it to the mark with water, shake well, filter it with filter paper, discard the first 20 mL of the solution, and collect the subsequent filtrate in a dry Erlenmeyer flask; Pipette 100 mL of the above filtrate and titrate it with 0.1 moL / L sodium thiosulfate solution until it turns light yellow, and continue titrating with starch solution as an indicator until it turns colorless as the end point;

[0060] Take another 50 mL of pure water and place it in a 250 mL brown volumetric flask for a blank test;

[0061] The concentration of methylene blue solution is calculated according to formula (a), and the calibration result is recorded as the calibration value C, with the unit g / L.

[0062] Concentration of methylene blue solution:

[0063] C = C 0 (V 1 - V) × 3.196 (a)

[0064] In the formula: C 0 — Concentration of sodium thiosulfate, mol / L;

[0065] V — Volume of sodium thiosulfate solution consumed in the blank test, mL;

[0066] V 1 — Volume of sodium thiosulfate solution consumed by the reagent, mL;

[0067] 319.6 — Molar mass of methylene blue (C 16 H 18 N 3 S·Cl), g / mol.

[0068] The measured value C 1 of the methylene blue solution concentration, with the unit g / L, is calculated according to formula (b):

[0069]

[0070] The test results are shown in Table 3.

[0071] Table 3 Methylene blue calibration results

[0072]

[0073] (2) Calculation of drug purity:

[0074] The calculation of drug purity is carried out according to the following steps:

[0075]

[0076] Among them, C 1 is the measured value of the concentration of the prepared methylene blue solution with a nominal concentration of 10 g / L (unit g / L), m represents the mass of the drug weighed (unit g), and the content (Ma, unit %) of methylene blue anhydrous (C 16 H 18 N 3 S·Cl) is calculated according to formula (c), and the drug purity of methylene blue trihydrate (C 16 H 18 N 3 S·Cl·3H 2 O) (M c, the unit is %) is calculated according to formula (d). The test results are shown in Table 4.

[0077] Table 4 Calibration Results of Methylene Blue Solution Reagent Purity

[0078]

[0079]

[0080] The purity of Drug No. 9 does not meet the user's requirements (C 16 H 18 N 3 S·Cl·3H 2 O content ≥ 30%), it will not be used, and other drugs will be selected according to step S1 for subsequent tests; the purities of Drugs No. 1, 2, 4, 5, 6, and 8 meet the user's requirements, and subsequent tests will be carried out according to S5.

[0081] Step S5: MB value test and correction: The prepared methylene blue solution with a nominal concentration of 10 g / L is measured according to GB / T 14684-2022, and the result is reserved to two decimal places. After the measurement, the MB value is corrected according to the calibration result of S4, and the result is reserved to one decimal place. The test results are shown in Table 5.

[0082] The calibrated value C of the methylene blue solution concentration, the MB correction value is calculated according to formula (d), and the MB value correction coefficient is

[0083]

[0084] Table 5 MB Correction Value Calculation and Results

[0085]

[0086] The technical solution of the present invention can quickly judge whether the prepared methylene blue solution meets the use requirements. By measuring the absorbance of the dilution (1.5 mg / L) of the prepared methylene blue solution and comparing it with the absorbance of the high-purity copper sulfate pentahydrate reagent at 2.8 g / L, it can be quickly determined whether the prepared solution reaches the prepared concentration. The technical solution of the present invention can quickly judge whether the purity of the original methylene blue reagent can meet the requirements. If the preparation process is correct and there is no obvious operation error, by calibrating the concentration of the prepared solution and calculating the purity of the drug, it can be determined whether the original drug reagent reaches the required purity. The technical solution of the present invention can quickly and accurately test the MB value. By measuring the concentration of the prepared methylene blue solution and correcting the MB value according to the measured concentration value, the correct value of the MB value can be found more accurately and quickly without re-preparing the solution and replacing better drugs.

[0087] The above-described embodiments merely represent several implementation manners of the present invention. The description thereof is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can be made on their own, and these all fall within the protection scope of the present invention.

Claims

1. A method for testing the concentration of methylene blue solution reagent for MB value detection of machine-made sand and correcting the MB value result, characterized in that: The following steps are involved: Step S1, preparation of drugs: selecting methylene blue chemical drugs with label purity ≥ 82%; Step S2, preparation of solution: preparing a methylene blue solution with a nominal concentration of 10 g / L; Step S3, absorbance measurement of the solution: 30 ml of a methylene blue solution with a nominal concentration of 10 g / L was taken and diluted with pure water in a 200 ml volumetric flask to prepare a methylene blue reagent solution with a nominal concentration of 1.5 g / L; 10 ml of the methylene blue solution was taken again and diluted with pure water in a 200 ml volumetric flask to prepare a methylene blue reagent solution with a nominal concentration of 1.5 g / L. 1.5g / L methylene blue solution is placed in a 200mL volumetric flask, diluted to the mark with pure water, and shaken; then accurately draw 20mL from the dilution into a 1000mL volumetric flask, dilute to the mark with pure water, shaken to make a 1.5mg / L reagent solution, and test the absorbance with a spectrophotometer; select a high-purity copper sulfate pentahydrate reagent or a standard reagent with a purity of more than 99.9% to prepare a reference solution with a concentration of 2.80g / 100ml, and measure its absorbance at a wavelength of 665nm and a light path of 1cm. The test is based on pure water; if the absorbance of the reagent solution differs from that of the reference solution within ±0.020, the prepared methylene blue solution with a concentration of 10g / L is directly used for the MB value test, and the MB value result does not need to be corrected; if the absorbance of the reagent solution differs from that of the reference solution by more than ±0.020, MB value detection and correction are required; MB value detection and correction includes the following steps: (1) Dilute the methylene blue solution with a nominal concentration of 10 g / L prepared in step S2 to obtain a methylene blue test solution with a nominal concentration of 1.5 g / L, calibrate it according to the iodine modified method to obtain the calibration value C of the methylene blue solution concentration, and calculate the purity of the drug; (2) MB value detection and correction: MB value detection is to use the prepared methylene blue solution with a nominal concentration of 10 g / L for MB value test; MB value correction is to combine the calibration value C of the methylene blue solution concentration in step (1) and calculate according to formula (e). The MB value correction coefficient is: : 。 2. The method for correcting the concentration of methylene blue solution reagent and the MB value result for testing the MB value of machine-made sand according to claim 1, characterized in that: Step (1) The concentration of the methylene blue solution is calibrated according to the iodine modified method, and the specific steps are as follows: 30 mL of the methylene blue solution with a nominal concentration of 10 g / L prepared in step S2 was taken and diluted in a 200 mL volumetric flask to prepare a methylene blue test solution with a nominal concentration of 1.5 g / L. 50 mL of the test solution was taken in a 250 mL brown volumetric flask, 25 mL of 36% acetic acid was added and shaken, 30 mL of 0.1 mol / L iodine standard solution was added, and shaken for 1 min. The brown volumetric flask was placed in a dark place for 1 h, shaken once every 10 min, diluted with water to the mark, shaken, filtered with filter paper, and 20 mL of the initial solution was discarded. The filtrate was then collected in a dry conical flask; 100 mL of the above filtrate was taken, and titrated with 0.1 mol / L sodium thiosulfate solution until it turned light yellow, and the starch solution was used as an indicator to continue titrating until it turned colorless as the end point; Take another 50mL of pure water and place it in a 250mL brown volumetric flask to do a blank test; The concentration of methylene blue solution is calculated according to formula (a), and the calibration result is recorded as calibration value C, in g / L. Methylene blue solution concentration: C = C0 (V1-V) × 3.196 (a) Where: C0—concentration of sodium thiosulfate, mol / L; V—volume of sodium thiosulfate solution consumed in blank test, mL; V1—volume of sodium thiosulfate solution consumed by the reagent, mL; 319.6—Methylene Blue C 16 H 18 Molar mass of N3S·Cl, g / mol.

3. The method for correcting the concentration of methylene blue solution reagent and the MB value result for testing the MB value of machine-made sand according to claim 1, characterized in that: The measured concentration C1 of the methylene blue solution with a nominal concentration of 10 g / L prepared in step (1) is in g / L and is calculated according to formula (b): ； Where C is the standardized concentration of methylene blue solution according to step (1).

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