Reagent concentration and MB value result correction method for detecting methylene blue solution for testing MB value of machine-made sand

Abstract

The invention discloses a detection methylene blue solution reagent concentration and MB value result correction method for testing the MB value of machine-made sand. The detection methylene blue solution reagent concentration and MB value result correction method comprises the following steps: preparing drugs; preparing a methylene blue solution with the nominal concentration of 10g / L; determining the absorbance of the solution; according to the technical scheme, the quality of the methylene blue reagent solution for MB value detection can be effectively controlled. By monitoring the concentration of the prepared solution, the test error caused by too low or too high concentration due to insufficient purity or improper preparation of the original medicine reagent can be effectively prevented, and the technical scheme provided by the invention can quickly judge whether the prepared methylene blue solution meets the use requirement or not. Whether the prepared solution reaches the preparation concentration or not is rapidly judged by determining the absorbance of the diluent (1.5 mg / L) of the prepared methylene blue solution and comparing the absorbance of the diluent (1.5 mg / L) with the absorbance of the high-purity copper sulfate pentahydrate reagent (2.8 g / L).

Description

Technical Field

[0001] The invention relates to the technical field of material performance detection, and in particular to a method for correcting the concentration of a methylene blue solution reagent used for testing the MB value of machine-made sand and a MB value result. Background Art

[0002] The methylene blue value in machine-made sand is an indicator used to determine whether the particles with a particle size of less than 0.075 mm in the machine-made sand are mainly soil 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 on stone powder and soil in machine-made sand. The amount of methylene blue adsorbed by stone powder is relatively small, while soil has a strong adsorption capacity for methylene blue. The content of soil in the machine-made sand can be determined by adding methylene blue solution to the machine-made sand and then observing the color change of the solution and the amount of methylene blue consumed.

[0003] The current national standard GB / T14684-2022 "Construction Sand" stipulates that the purity of methylene blue (C 16 H 18 N 3 S·Cl·3H 2 O) is greater than 98.5%, which has high requirements for reagents. After investigation, it was found that although most reagents on the market meet the label requirements, the actual purity cannot meet the requirements. The specification does not specify the means to control the quality of the reagents; the concentration of the prepared methylene blue reagent is not calibrated and quality controlled, and it is impossible to determine that the prepared solution has reached the specified concentration, which in turn affects the MB value results; it does not involve the correction of MB value results.

[0004] The standard JGJ52-2006 "Standard for Sand, Quality and Inspection Methods for Ordinary Concrete" does not specify the purity requirements for methylene blue. After investigation, it was found that most reagents on the market cannot meet the purity requirements, and the specification does not specify 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 results; further, it does not involve the correction of the MB value results.

[0005] If the purity of the methylene blue reagent is not controlled, it will have a significant impact on the MB value test results, thereby affecting the performance of concrete. The above national standards and industry standards do not mention the calibration of the prepared methylene blue concentration, 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 the "Test Method for Methylene Blue Adsorption Value of Wood Activated Carbon" GB / T12496.10 and the "Test Method for Methylene Blue Adsorption Value of Coal-Based Granular Activated Carbon" GB / T7702.6, the calibration method for the purity of methylene blue reagent is not specified, and the concentration required for methylene blue calibration is different from the concentration of methylene blue solution used for the detection of MB value of machine-made sand, and the preparation method is also different, and it may not be suitable for the accuracy detection of MB value of machine-made sand. GB / T12496.10 also proposed a method for calibrating methylene blue solution by absorbance, which is also involved in GB / T7702.6-2008, but it is old and may not be applicable to the calibration of methylene blue reagent solution for MB test of machine-made sand. The 2020 edition of the "Chinese Pharmacopoeia" has a standard for methylene blue (C 16 H 18 CIN 3 However, the scope of application may not be related to the MB value test of machine-made sand.

[0007] In the non-building materials field, the fields used are different and there are applicable prerequisites: the content of methylene blue indicator used in the preparation of methylene blue test solution is above 98.5%, and it must be prepared in strict accordance with the standard GB / T12496.10 Section 5.5.1, and the calibrated concentration is 1.5g / L; the technical indicators of anhydrous copper sulfate concentration by spectrophotometer method in Section 8.3 are outdated and all dilutions are different, so they have been reconfirmed with pure water as the dilution.

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

[0009] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a method for testing the concentration of a methylene blue solution reagent for the MB value of machine-made sand and a method for correcting the MB value results, which can not only quickly test the concentration of the prepared methylene blue solution and reduce the amount of sample and methylene blue solution, but also quickly determine the purity of the original methylene blue drug, and improve the accuracy of the MB value of the machine-made sand methylene blue and reduce errors, thereby making up for the deficiencies of standards and the industry.

[0010] In view of the shortcomings of the prior art, the present invention provides a method for testing the concentration of a methylene blue solution reagent for detecting the MB value of machine-made sand and correcting the MB value result, comprising the following steps:

[0011] Step S1, drug preparation: select the label purity ≥ 82% (hereinafter referred to as C 16 H 18 N 3 S·Cl·3H 2 O) of methylene blue chemicals;

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

[0013] 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 20mL of the diluted solution is accurately drawn into a 1000mL volumetric flask, diluted to the mark with pure water, shaken to make a 1.5mg / L reagent solution, and the absorbance is tested with a spectrophotometer; a high-purity copper sulfate pentahydrate reagent or a standard reagent with a purity of more than 99.9% is selected to prepare a reference solution with a concentration of 2.80g / 100mL, and its absorbance is measured at a wavelength of 665nm and a light path of 1cm. The test is all 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.

[0014] Furthermore, the MB value detection and correction includes the following steps:

[0015] (1) Calibration of methylene blue solution concentration and calculation of purity: The methylene blue solution with a nominal concentration of 10 g / L prepared in step S2 is used to calibrate and calculate the purity of the drug according to the improved iodine titration method;

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

[0017] Furthermore, the concentration of the methylene blue solution in step (1) is calibrated according to the iodine modified method, and the specific steps are as follows:

[0018] 30 mL of the methylene blue solution with a nominal concentration of 10 g / L prepared in step S2 is 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 is taken in a 250 mL brown volumetric flask, 25 mL of 36% acetic acid is added and shaken, 30 mL of 0.1 mol / L iodine standard solution is added, and shaken for 1 min. The brown volumetric flask is 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 is discarded. The filtrate is then collected in a dry conical flask; 100 mL of the above filtrate is taken, and titrated with 0.1 mol / L sodium thiosulfate solution until it turns light yellow, and the starch solution is used as an indicator to continue titrating until it turns colorless as the end point;

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

[0020] 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.

[0021] Methylene blue solution concentration:

[0022] C=C 0 (V 1 -V)×3.196 (a)

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

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

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

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

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

[0028]

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

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

[0031]

[0032]

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

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

[0035] Furthermore, the MB value correction in step (2) is calculated by combining the calibration value C of the methylene blue solution concentration in step (1) according to formula (e), 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 the experimental error caused by the 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 use requirements. By measuring the absorbance of the prepared methylene blue solution dilution (1.5 mg / L) and comparing it with the absorbance of the high-purity copper sulfate pentahydrate reagent 2.8 g / L, it can be quickly determined 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 operating 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 has reached 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 actual measured concentration value, the correct MB value can be found more accurately and quickly without the need to re-prepare the solution or replace it with a better drug. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0043] Figure 2 It is a schematic diagram of the method flow in Example 1. DETAILED DESCRIPTION

[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: Absorbance determination of solution: 30mL of methylene blue solution with a nominal concentration of 10g / L is taken and diluted with pure water in a 200mL volumetric flask to prepare a methylene blue reagent solution with a nominal concentration of 1.5g / L; 10mL of 1.5g / L methylene blue solution is taken again in a 200mL volumetric flask, diluted to the mark with pure water, and shaken; 20mL of the dilution is accurately taken into a 1000mL volumetric flask, diluted to the mark with pure water, shaken to prepare a 1.5mg / L reagent solution, and the absorbance is tested with a spectrophotometer; a high-purity copper sulfate pentahydrate reagent or a reference reagent with a purity of more than 99.9% is selected to prepare a reference solution with a concentration of 2.80g / 100mL, and its absorbance is measured at a wavelength of 665nm and a light path of 1cm. The test is all based on pure water. The test results are shown in Table 2.

[0054] Table 2 Methylene blue absorbance test results

[0055]

[0056] Since the absorbance of No. 3 and No. 7 differed from that of the reference solution by no more than ±0.020, the prepared methylene blue solution with a nominal concentration of 10 g / L was directly measured according to the determination method of the methylene blue value of machine-made sand specified in GB / T 14684-2022. The measurement results were: MB value of No. 3 was 0.5, and MB value of No. 7 was 0.5.

[0057] Step S4: calibration of solution concentration and calculation of drug purity: using the methylene blue solution with a nominal concentration of 10 g / L prepared above, calibration and drug purity calculation are performed according to the iodine volume modified method. The specific steps are as follows:

[0058] (1) Calibration of solution concentration:

[0059] 30 ml of the methylene blue solution with a nominal concentration of 10 g / L prepared in step S2 is 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 is taken in a 250 ml brown volumetric flask, 25 ml of 36% acetic acid is added and shaken, 30 ml of 0.1 mol / L iodine standard solution is added, and shaken for 1 min. The brown volumetric flask is 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 is discarded. The filtrate is then collected in a dry conical flask; 100 ml of the above filtrate is taken, and titrated with 0.1 mol / L sodium thiosulfate solution until it turns light yellow, and the starch solution is used as an indicator to continue titrating until it turns colorless as the end point;

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

[0061] 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.

[0062] Methylene blue solution concentration:

[0063] C=C 0 (V 1 -V)×3.196 (a)

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

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

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

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

[0068] Measured value of methylene blue solution concentration C 1 , unit g / L, 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 prepared nominal concentration of 10g / L methylene blue solution (in g / L), m represents the weighing mass of the drug (in g), and the drug purity is methylene blue anhydrate (C 16 H 18 N 3 The content of S·Cl) (Ma, unit %) is calculated according to formula (c), and the purity of the drug methylene blue tricompound (C 16 H 18 N 3 S·Cl·3H 2 O)(M c, unit %) is calculated according to formula (d). The test results are shown in Table 4.

[0077] Table 4 Methylene blue solution reagent purity calibration results

[0078]

[0079]

[0080] The purity of drug No. 9 does not meet the needs of users (C 16 H 18 N 3 S·Cl·3H 2 O content ≥30%), it will not be used, and other drugs will be selected for subsequent testing according to step S1; if the purity of drugs No. 1, 2, 4, 5, 6, and 8 meets the user's requirements, subsequent testing 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 / T14684-2022, and the result is retained to two digits. After the measurement is completed, the MB value is corrected according to the calibration result of S4, and the result is retained to one decimal place. The test results are shown in Table 5.

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

[0083]

[0084] Table 5 MB correction value calculation and results

[0085]

[0086] The technical solution of the present invention can quickly determine whether the prepared methylene blue solution meets the use requirements. By measuring the absorbance of the prepared methylene blue solution dilution (1.5 mg / L) and comparing the absorbance of the high-purity copper sulfate pentahydrate reagent 2.8 g / L, it is quickly determined whether the prepared solution reaches the preparation concentration. The technical solution of the present invention can quickly determine whether the purity of the original methylene blue reagent can reach the requirements. If the preparation process is correct and there is no obvious operating 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, the MB value is corrected according to the actual measured value of the concentration, and the correct value of the MB value is found more accurately and quickly, without the need to re-prepare the solution and replace better drugs.

[0087] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to 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 20mL of the diluted solution is accurately drawn into a 1000mL volumetric flask, diluted to the mark with pure water, shaken to make a 1.5mg / L reagent solution, and the absorbance is tested with a spectrophotometer; a high-purity copper sulfate pentahydrate reagent or a standard reagent with a purity of more than 99.9% is selected to prepare a reference solution with a concentration of 2.80g / 100ml, and its absorbance is measured at a wavelength of 665nm and a light path of 1cm. The test is all 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.

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: MB value detection and correction includes the following steps: (1) Calibration of methylene blue solution concentration and calculation of purity: The methylene blue solution with a nominal concentration of 10 g / L prepared in step S2 is used to calibrate and calculate the purity of the drug according to the iodine-based modified method; (2) MB value detection and correction.

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 2, 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 is 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 is taken in a 250 mL brown volumetric flask, 25 mL of 36% acetic acid is added and shaken, 30 mL of 0.1 mol / L iodine standard solution is added, and shaken for 1 min. The brown volumetric flask is 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 is discarded. The filtrate is then collected in a dry conical flask; 100 mL of the above filtrate is taken, and titrated with 0.1 mol / L sodium thiosulfate solution until it turns light yellow, and the starch solution is used as an indicator to continue titrating until it turns colorless as the end point; Take another 50mL of pure water and place it in a 250mL brown volumetric flask as a blank test; The concentration of methylene blue solution is calculated according to formula (a). The calibration result is recorded as calibration value C, in g / L. The concentration of methylene blue solution is: 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.

4. 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 2, 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).

5. 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 2, characterized in that: Step (1) The calculation of the purity of the methylene blue solution is carried out according to the following steps: Where C1 is the measured value of the prepared methylene blue solution with a nominal concentration of 10 g / L (in g / L), m represents the weighed mass of the drug (in g), and the purity of the drug is methylene blue anhydrate (C 16 H 18 The content of N3S·Cl) (Ma, unit %) is calculated according to formula (c), and the purity of the drug methylene blue tricompound (C 16 H 18 N3S·Cl·3H2O)(M c , unit %) is calculated according to formula (d).

6. 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 2, characterized in that: In step (2), the MB value test is to use a methylene blue solution with a nominal concentration of 10 g / L for the MB value test.

7. 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 2, characterized in that: The MB value correction in step (2) is calculated by combining the calibration value C of the methylene blue solution concentration in step (1) according to formula (e). The MB value correction coefficient is:

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