Method for detecting halogen concentration in liquid chloromethane

Abstract

The invention discloses a method for detecting the concentration of halogen in liquid chloromethane, which comprises the following steps: S1, preparing an acetic acid-sodium acetate buffer solution, a phenol red solution, a chloramine-T solution and a sodium thiosulfate solution for later use, volatilizing the to-be-detected liquid chloromethane with a fixed volume at normal temperature, and then adding water to dilute the to-be-detected liquid chloromethane to the original volume so as to obtain a test solution A; taking the test solution A with the volume of W1, adding hydrochloric acid to adjust the pH value to 4.4-5, adding water to dilute until the volume is W2, and uniformly shaking to obtain a test solution B; s2, taking N groups of test solutions B, respectively adding an acetic acid-sodium acetate buffer solution with the volume of K1 and a phenol red solution with the volume of K2 into each group of test solutions B, uniformly shaking, adding a chloramine-T solution with the volume of K3, uniformly shaking, adding a sodium thiosulfate solution with the volume of K4, uniformly shaking, adding water to dilute until the volume is W0, uniformly shaking, and standing to obtain N groups of solutions to be detected, and respectively measuring the absorbance of each group of solution to be measured at the wavelength lambda. The method can accurately detect the concentration of the halogen in the liquid chloromethane.

Description

Technical Field

[0001] The invention relates to a method for detecting the halogen concentration in liquid chloromethane. Background Art

[0002] Currently, methyl chloride is a colorless, transparent liquid. When the color of liquid methyl chloride is unacceptable, such as when it turns pale yellow, it is necessary to measure the halogen concentration in the liquid methyl chloride to help identify the problem in the production process and take appropriate measures. However, a search revealed that there is currently a lack of a method for accurately measuring the halogen concentration in liquid methyl chloride, resulting in an inability to accurately measure the halogen concentration in liquid methyl chloride. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to overcome the defects of the prior art and provide a method for detecting the concentration of halogen in liquid chloromethane, which can accurately detect the concentration of halogen in liquid chloromethane.

[0004] In order to solve the above technical problems, the technical solution of the present invention is: a method for detecting the halogen concentration in liquid chloromethane, the method comprising the following steps:

[0005] S1: Prepare acetic acid-sodium acetate buffer solution, phenol red solution, chloramine-T solution and sodium thiosulfate solution for use, and volatilize a fixed volume of the liquid chloromethane to be tested at room temperature, then dilute with water to the original volume to prepare test solution A, take a volume of W1 of test solution A and add hydrochloric acid to adjust the pH value to 4.4-5, then dilute with water to a volume of W2 and shake well to prepare test solution B;

[0006] S2: Take N groups of test solution B, wherein the volume of the i-th group of test solution B is Vi, 1≤i≤N, N≥1, and first add acetic acid-sodium acetate buffer solution with a volume of K1 and phenol red solution with a volume of K2 to each group of test solution B and shake up, then add chloramine-T solution with a volume of K3 and shake up, then add sodium thiosulfate solution with a volume of K4 and shake up, then dilute with water to a volume of W0 and shake up and let stand to obtain N groups of test solutions, respectively measure the absorbance of each group of test solutions at a wavelength λ, and compare the absorbance of each group of test solutions with the drawn absorbance-halogen content standard curve to obtain the halogen content in each group of test solutions, wherein the halogen content in the i-th group of test solutions is recorded as Xi;

[0007] S3: The concentration of halogen in the liquid chloromethane to be tested is obtained as

[0008] Among them, the method for drawing the absorbance-halogen content standard curve is: taking multiple groups of halogen standard solutions with different volumes and a mass concentration of C as samples, obtaining the halogen content in each group of samples according to the volume and mass concentration C of the halogen standard solution in each group of samples, first adding a volume of K1 of acetic acid-sodium acetate buffer solution and a volume of K2 of phenol red solution to each group of samples and shaking them well, then adding a volume of K3 of chloramine-T solution and shaking them well, then adding a volume of K4 of sodium thiosulfate solution and shaking them well, then diluting with water to a volume of W0 and shaking and standing, then measuring the absorbance of each group of samples at a wavelength λ, and drawing an absorbance-halogen content standard curve according to the absorbance of each group of samples and the halogen content in each group of samples.

[0009] Furthermore, the method further comprises the steps of:

[0010] S4: Take a volume of W3 of test solution B as the blank group, take a volume of W3 of test solution B in group M as the control group, add a halogen standard solution with a mass concentration of C to the control group in group M, and do not add a halogen standard solution to the blank group; wherein, the volume of the halogen standard solution added to the j-th control group is Uj, 1≤j≤M, M≥1;

[0011] To the blank group and each control group, respectively, add a volume of K1 of acetic acid-sodium acetate buffer solution and a volume of K2 of phenol red solution and shake well, then add a volume of K3 of chloramine-T solution and shake well, then add a volume of K4 of sodium thiosulfate solution and shake well, then dilute with water to a volume of W0 and shake well and let stand, then measure the absorbance of the blank group solution and each control group solution at wavelength λ, and compare the absorbance of the blank group solution with the absorbance-halogen content standard curve to obtain the halogen content Y0 in the blank group solution, and compare the absorbance of each group of control group solutions with the absorbance-halogen content standard curve to obtain the halogen content in each group of control group solutions; wherein, the halogen content in the jth group of control group solutions is recorded as Yj;

[0012] Obtain the spiked recovery rate of each control group; wherein, the spiked recovery rate of the j-th control group Pj = [(Yj-Y0) / (Uj·C)]×100%.

[0013] Furthermore, K1 is 0.5 ml, K2 is 0.4 ml, K3 is 1 ml, K4 is 1 ml, W0 is 25 ml, wavelength λ is 590 nm, mass concentration C is 4 ug / ml, W1 is 20 ml, and W2 is 100 ml.

[0014] Furthermore, the specific operations of step S4 are:

[0015] Take a volume of W3 of test solution B and place it in a 25ml colorimetric tube as the blank group. Take a volume of W3 of test solution B in group M and place it in a 25ml colorimetric tube as the control group. Add a halogen standard solution with a mass concentration of 4ug / ml to the control group in group M, while do not add a halogen standard solution to the blank group. Among them, the volume of the halogen standard solution added to the control group in group j is Uj;

[0016] To the colorimetric tube of the blank group and the colorimetric tube of each control group, respectively, 0.5 ml of acetic acid-sodium acetate buffer solution and 0.4 ml of phenol red solution were first added and shaken, then 1 ml of chloramine-T solution was added and immediately shaken for 2 minutes, then 1 ml of sodium thiosulfate solution was added and shaken for 15 seconds, and then diluted with water to the scale of the colorimetric tube, shaken and allowed to stand for 15 minutes, and then the absorbance of the blank group solution and each control group solution at 590 nm was measured respectively, and the halogen content Y0 in the blank group solution was obtained by comparing the absorbance of the blank group solution with the absorbance-halogen content standard curve, and the halogen content in each group of control group solutions was obtained by comparing the absorbance of each group of control group solutions with the absorbance-halogen content standard curve; wherein, the halogen content in the jth group of control group solutions is recorded as Yj;

[0017] Obtain the spiked recovery rate of each control group; wherein, the spiked recovery rate of the j-th control group Pj = [(Yj-Y0) / (Uj·C)]×100%.

[0018] Furthermore, the specific operation of step S2 is: take N groups of test solution B and place them in 25 ml colorimetric tubes respectively, wherein the volume of the i-th group of test solution B is Vi, first add 0.5 ml of acetic acid-sodium acetate buffer solution and 0.4 ml of phenol red solution to the test solution B in each colorimetric tube and shake well, then add 1 ml of chloramine-T solution and immediately shake well for 2 minutes, then add 1 ml of sodium thiosulfate solution and shake well for 15 seconds, then add water to the colorimetric tube to dilute to the scale and then shake and stand for 15 minutes, thereby obtaining N groups of test solutions, respectively measuring the absorbance of each group of test solutions at 590 nm, and comparing the absorbance of each group of test solutions with the drawn absorbance-halogen content standard curve to obtain the halogen content in each group of test solutions; wherein the halogen content in the i-th group of test solutions is recorded as Xi.

[0019] Furthermore, the specific method for drawing the absorbance-halogen content standard curve is as follows: take multiple groups of 4ug / ml halogen standard solutions of different volumes as samples and place them in 25ml colorimetric tubes respectively, obtain the halogen content in each group of samples according to the volume and mass concentration of the halogen standard solution in each group of samples, first add 0.5ml of acetic acid-sodium acetate buffer solution and 0.4ml of phenol red solution to the sample in each colorimetric tube and shake well, then add 1ml of chloramine-T solution and immediately shake well for 2 minutes, then add 1ml of sodium thiosulfate solution and shake well for 15 seconds, then add water to the colorimetric tube to dilute to the scale and then shake and let stand for 15 minutes, then measure the absorbance of each group of samples at 590nm, and draw the absorbance-halogen content standard curve according to the absorbance of each group of samples and the halogen content in each group of samples.

[0020] Furthermore, the specific operation of preparing test solution A in step S1 is: placing 250 ml of the liquid chloroform to be tested in an environment below 40° C. to evaporate until the liquid volume is less than 5 ml, then transferring it to a 250 ml volumetric flask and diluting it to the scale with water to prepare test solution A.

[0021] Furthermore, the specific operation of preparing test solution B in step S1 is as follows: taking 20 ml of test solution A into a beaker, adding hydrochloric acid to the beaker to adjust the pH value to 4.6, then transferring the solution in the beaker into a 100 ml volumetric flask, diluting the volume with water to the scale, shaking well and setting aside to prepare test solution B.

[0022] Furthermore, step S1 also includes: preparing a halogen standard solution with a mass concentration of C for standby use.

[0023] Further, the steps for preparing a halogen standard solution with a mass concentration of 4ug / ml are as follows:

[0024] Prepare 0.1 mg / ml halogen standard solution and store in a brown bottle;

[0025] Pipette 4 ml of 0.1 mg / ml halogen standard solution into a 100 ml brown volumetric flask and dilute to the mark with water to obtain a 4 ug / ml halogen standard solution.

[0026] Further, in step S1, the pH value of the prepared acetic acid-sodium acetate buffer solution is 4.6, the concentration of the prepared phenol red solution is 0.24 g / L, the concentration of the prepared chloramine-T solution is 2 g / L, and the concentration of the prepared sodium thiosulfate solution is 2.5 g / L.

[0027] After adopting the above technical solution, the halogen concentration in the test solution A can be obtained according to the formula Xi / [Vi·(W1 / W2)]. Because the test solution A is obtained by volatilizing the liquid methyl chloride and then diluting it with water to the original volume, the halogen concentration in the test solution A is the same as the halogen concentration in the liquid methyl chloride to be tested. Therefore, the halogen concentration in the liquid methyl chloride to be tested can be obtained by taking the average of the halogen concentrations in multiple test solutions A, thereby accurately detecting the halogen concentration in the liquid methyl chloride. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is the absorbance-halogen content standard curve in a specific embodiment of the present invention. DETAILED DESCRIPTION

[0029] The present invention provides a method for detecting the halogen concentration in liquid chloromethane. Those skilled in the art can refer to the content of this article and appropriately improve the parameters to achieve the desired result. It should be noted that all similar substitutions and modifications are obvious to those skilled in the art and fall within the scope of protection of the present invention. The method of the present invention has been described through examples, and relevant personnel can obviously modify or appropriately change and combine the method herein without departing from the content, spirit and scope of the present invention to implement and apply the technology of the present invention.

[0030] The present invention provides a method for detecting the halogen concentration in liquid chloromethane, the method comprising the following steps:

[0031] S1: Prepare acetic acid-sodium acetate buffer solution, phenol red solution, chloramine-T solution and sodium thiosulfate solution for use, and volatilize a fixed volume of the liquid chloromethane to be tested at room temperature, then dilute with water to the original volume to prepare test solution A, take a volume of W1 of test solution A and add hydrochloric acid to adjust the pH value to 4.4-5, then dilute with water to a volume of W2 and shake well to prepare test solution B;

[0032] S2: Take N groups of test solution B, wherein the volume of the i-th group of test solution B is Vi, 1≤i≤N, N≥1, and first add acetic acid-sodium acetate buffer solution with a volume of K1 and phenol red solution with a volume of K2 to each group of test solution B and shake up, then add chloramine-T solution with a volume of K3 and shake up, then add sodium thiosulfate solution with a volume of K4 and shake up, then dilute with water to a volume of W0 and shake up and let stand to obtain N groups of test solutions, respectively measure the absorbance of each group of test solutions at a wavelength λ, and compare the absorbance of each group of test solutions with the drawn absorbance-halogen content standard curve to obtain the halogen content in each group of test solutions, wherein the halogen content in the i-th group of test solutions is recorded as Xi;

[0033] S3: The concentration of halogen in the liquid chloromethane to be tested is obtained as

[0034] Among them, the method for drawing the absorbance-halogen content standard curve is: taking multiple groups of halogen standard solutions with different volumes and a mass concentration of C as samples, obtaining the halogen content in each group of samples according to the volume and mass concentration C of the halogen standard solution in each group of samples, first adding a volume of K1 of acetic acid-sodium acetate buffer solution and a volume of K2 of phenol red solution to each group of samples and shaking them well, then adding a volume of K3 of chloramine-T solution and shaking them well, then adding a volume of K4 of sodium thiosulfate solution and shaking them well, then diluting with water to a volume of W0 and shaking and standing, then measuring the absorbance of each group of samples at a wavelength λ, and drawing an absorbance-halogen content standard curve according to the absorbance of each group of samples and the halogen content in each group of samples.

[0035] Specifically, the acetic acid-sodium acetate buffer solution, phenol red solution, chloramine-T solution, and sodium thiosulfate solution added to each group of test solution B, and the acetic acid-sodium acetate buffer solution, phenol red solution, chloramine-T solution, and sodium thiosulfate solution added to each group of samples are all prepared in step S1. More specifically, the halogen concentration in test solution A can be obtained according to the formula Xi / [Vi·(W1 / W2)]. Because test solution A is obtained by diluting the liquid chloromethane to be tested with water after volatilization, the halogen concentration in test solution A is the same as the halogen concentration in the liquid chloromethane to be tested. Therefore, the halogen concentration in the liquid chloromethane to be tested can be obtained by averaging the halogen concentrations in the multiple test solutions A. Therefore, the concentration of halogen in liquid chloromethane can be accurately detected.

[0036] Specifically, the method further includes the following steps:

[0037] S4: Take a volume of W3 of test solution B as the blank group, take a volume of W3 of test solution B in group M as the control group, add a halogen standard solution with a mass concentration of C to the control group in group M, and do not add a halogen standard solution to the blank group; wherein, the volume of the halogen standard solution added to the j-th control group is Uj, 1≤j≤M, M≥1;

[0038] To the blank group and each control group, respectively, add a volume of K1 of acetic acid-sodium acetate buffer solution and a volume of K2 of phenol red solution and shake well, then add a volume of K3 of chloramine-T solution and shake well, then add a volume of K4 of sodium thiosulfate solution and shake well, then dilute with water to a volume of W0 and shake well and let stand, then measure the absorbance of the blank group solution and each control group solution at wavelength λ, and compare the absorbance of the blank group solution with the absorbance-halogen content standard curve to obtain the halogen content Y0 in the blank group solution, and compare the absorbance of each group of control group solutions with the absorbance-halogen content standard curve to obtain the halogen content in each group of control group solutions; wherein, the halogen content in the jth group of control group solutions is recorded as Yj;

[0039] Obtain the spiked recovery of each control group; where the spiked recovery of the jth control group, Pj, is [(Yj - Y0) / (Uj·C)] × 100%. The acetic acid-sodium acetate buffer solution, phenol red solution, chloramine-T solution, and sodium thiosulfate solution added to the blank group and each control group are all prepared in step S1.

[0040] Among them, K1 is 0.5ml, K2 is 0.4ml, K3 is 1ml, K4 is 1ml, W0 is 25ml, wavelength λ is 590nm, mass concentration C is 4ug / ml, W1 is 20ml, and W2 is 100ml.

[0041] Specifically, the specific operations of step S4 are:

[0042] Take a volume of W3 of test solution B and place it in a 25ml colorimetric tube as the blank group. Take a volume of W3 of test solution B in group M and place it in a 25ml colorimetric tube as the control group. Add a halogen standard solution with a mass concentration of 4ug / ml to the control group in group M, while do not add a halogen standard solution to the blank group. Among them, the volume of the halogen standard solution added to the control group in group j is Uj;

[0043] To the colorimetric tube of the blank group and the colorimetric tube of each control group, respectively, 0.5 ml of acetic acid-sodium acetate buffer solution and 0.4 ml of phenol red solution were first added and shaken, then 1 ml of chloramine-T solution was added and immediately shaken for 2 minutes, then 1 ml of sodium thiosulfate solution was added and shaken for 15 seconds, and then diluted with water to the scale of the colorimetric tube, shaken and allowed to stand for 15 minutes, and then the absorbance of the blank group solution and each control group solution at 590 nm was measured respectively, and the halogen content Y0 in the blank group solution was obtained by comparing the absorbance of the blank group solution with the absorbance-halogen content standard curve, and the halogen content in each group of control group solutions was obtained by comparing the absorbance of each group of control group solutions with the absorbance-halogen content standard curve; wherein, the halogen content in the jth group of control group solutions is recorded as Yj;

[0044] Obtain the spiked recovery rate of each control group; wherein, the spiked recovery rate of the j-th control group Pj = [(Yj-Y0) / (Uj·C)]×100%.

[0045] Specifically, the specific operation of step S2 is: take N groups of test solution B and place them in 25 ml colorimetric tubes respectively, wherein the volume of the i-th group of test solution B is Vi, first add 0.5 ml of acetic acid-sodium acetate buffer solution and 0.4 ml of phenol red solution to the test solution B in each colorimetric tube and shake well, then add 1 ml of chloramine-T solution and immediately shake well for 2 minutes, then add 1 ml of sodium thiosulfate solution and shake well for 15 seconds, then add water to the colorimetric tube to dilute to the scale and then shake and stand for 15 minutes, thereby obtaining N groups of test solutions, respectively measuring the absorbance of each group of test solutions at 590 nm, and comparing the absorbance of each group of test solutions with the drawn absorbance-halogen content standard curve to obtain the halogen content in each group of test solutions; wherein the halogen content in the i-th group of test solutions is recorded as Xi.

[0046] Specifically, the specific method for drawing the absorbance-halogen content standard curve is as follows: take multiple groups of 4ug / ml halogen standard solutions of different volumes as samples and place them in 25ml colorimetric tubes respectively, obtain the halogen content in each group of samples according to the volume and mass concentration of the halogen standard solution in each group of samples, first add 0.5ml of acetic acid-sodium acetate buffer solution and 0.4ml of phenol red solution to the sample in each colorimetric tube and shake well, then add 1ml of chloramine-T solution and immediately shake well for 2 minutes, then add 1ml of sodium thiosulfate solution and shake well for 15 seconds, then add water to the colorimetric tube to dilute to the scale and then shake and let stand for 15 minutes, then measure the absorbance of each group of samples at 590nm, and draw an absorbance-halogen content standard curve according to the absorbance of each group of samples and the halogen content in each group of samples.

[0047] Specifically, the specific operation of preparing test solution A in step S1 is: placing 250 ml of the liquid chloroform to be tested in an environment below 40° C. to evaporate until the liquid volume is less than 5 ml, then transferring it to a 250 ml volumetric flask and diluting it to the scale with water to prepare test solution A.

[0048] Specifically, the specific operation of preparing test solution B in step S1 is as follows: taking 20 ml of test solution A into a beaker, adding hydrochloric acid to the beaker to adjust the pH value to 4.6, then transferring the solution in the beaker to a 100 ml volumetric flask, diluting the volume with water to the mark, shaking well and setting aside to prepare test solution B. The hydrochloric acid added to the beaker is a dilute hydrochloric acid with a concentration of (1+10), and the pH value of the solution in the beaker needs to be tested with a pH meter when adjusting the pH value.

[0049] Specifically, step S1 further includes: preparing a halogen standard solution with a mass concentration of C for standby use; wherein the steps of preparing a halogen standard solution with a mass concentration of 4ug / ml are:

[0050] Prepare 0.1 mg / ml halogen standard solution and store in a brown bottle;

[0051] Pipette 4 ml of 0.1 mg / ml halogen standard solution into a 100 ml brown volumetric flask and dilute to the mark with water to obtain a 4 ug / ml halogen standard solution.

[0052] Specifically, in step S1, the pH value of the prepared acetic acid-sodium acetate buffer solution is 4.6, the concentration of the prepared phenol red solution is 0.24 g / L, the concentration of the prepared chloramine-T solution is 2 g / L, and the concentration of the prepared sodium thiosulfate solution is 2.5 g / L. In this embodiment, chloramine-T is used as an oxidant to oxidize halogen ions into free halides, which then react with phenol red to form tetrahalophenol red. The color of the solution varies from yellow-green to purple depending on the halogen ion concentration, which is used for photometric determination.

[0053] Specifically, the step of preparing acetic acid-sodium acetate buffer solution in step S1 is: weighing 164g sodium acetate trihydrate and dissolving it in water, adding 84ml acetic acid and diluting it to 1000ml, then detecting the pH value with a pH meter and adding glacial acetic acid to adjust the pH value to 4.6. Specifically, the step of preparing 0.24g / L phenol red solution in step S1 is: weighing 0.024g phenol red and 0.12g sodium carbonate in the same beaker, adding 20mL distilled water to the beaker to dissolve it and then diluting it to 100ml. If the solution is not clear at this time, it needs to be filtered before use. Specifically, the step of preparing 2g / L ammonia amine-T solution in step S1 is: weighing 0.2g chloramine-T, dissolving it in distilled water and diluting it to 100ml, and then storing it in a brown bottle for refrigeration. Specifically, the step of preparing 25g / L sodium thiosulfate solution in step S1 is: weighing 2.5g sodium thiosulfate, dissolving it in distilled water and diluting it to 100ml.

[0054] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below based on specific embodiments.

[0055] In this specific embodiment, K1 is 0.5 ml, K2 is 0.4 ml, K3 is 1 ml, K4 is 1 ml, W1 is 20 ml, W2 is 100 ml, W3 is 1 ml, W0 is 25 ml, the wavelength λ is 590 nm, and the mass concentration C is 4 ug / ml.

[0056] The method for detecting the halogen concentration in the liquid chloromethane of this specific embodiment is:

[0057] Prepare an acetic acid-sodium acetate buffer solution with a pH value of 4.6, a 0.24g / L phenol red solution, a 2g / L chloramine-T solution, a 25g / L sodium thiosulfate solution, and a halogen standard solution with a mass concentration of 4ug / ml for use. The steps for preparing the acetic acid-sodium acetate buffer solution with a pH value of 4.6 are as follows: weigh 164g of sodium acetate trihydrate and dissolve it in water, add 84ml of acetic acid and dilute to 1000ml, then use a pH meter to detect the pH value and add glacial acetic acid to adjust the pH value to 4.6. The steps for preparing a 0.24g / L phenol red solution are as follows: weigh 0.024g of phenol red and 0.12g of sodium carbonate in the same beaker, add 20mL of distilled water to the beaker to dissolve it, and then dilute to 100ml. If the solution is not clear at this time, it needs to be filtered before use. The steps for preparing a 2g / L ammonia-T solution are: weigh 0.2g of chloramine-T, dissolve it in distilled water, dilute it to 100ml, and store it in a brown bottle under refrigeration. The steps for preparing a 25g / L sodium thiosulfate solution are: weigh 2.5g of sodium thiosulfate, dissolve it in distilled water, and dilute it to 100ml. The steps for preparing a halogen standard solution with a mass concentration of 4ug / ml are:

[0058] Prepare 0.1 mg / ml halogen standard solution and store in a brown bottle;

[0059] Pipette 4 ml of 0.1 mg / ml halogen standard solution into a 100 ml brown volumetric flask and dilute to the mark with water to obtain a 4 ug / ml halogen standard solution.

[0060] Draw the absorbance-halogen content standard curve. The specific operation is: take 6 groups of 4ug / ml halogen standard solutions with volumes of 1ml, 2ml, 4ml, 6ml, 8ml and 10ml respectively as samples and place them in 6 25ml colorimetric tubes respectively. According to the volume and mass concentration of the halogen standard solutions in the 6 groups of samples, the halogen contents in the 6 groups of samples are 4ug, 8ug, 16ug, 24ug, 32ug and 40ug respectively. To the sample in each colorimetric tube, 0.5 ml of acetic acid-sodium acetate buffer solution and 0.4 ml of phenol red solution were added and shaken, then 1 ml of chloramine-T solution was added and immediately shaken for 2 minutes, then 1 ml of sodium thiosulfate solution was added and shaken for 15 seconds, then water was added to the colorimetric tube to dilute to the scale and then shaken and allowed to stand for 15 minutes, and then the absorbance of the six groups of samples at 590 nm was measured, and the results were 0.035, 0.0639, 0.1301, 0.1955, 0.262 and 0.3376 respectively. The halogen content and absorbance of each group of samples are listed in Table 1. Then, according to the absorbance of each group of samples and the halogen content in each group of samples, the absorbance-halogen content standard curve was drawn as shown in FIG. Figure 1 shown.

[0061] Table 1

[0062] absorbance 0.035 0.0639 0.1301 0.1955 0.262 0.3376 Halogen content ug 4 8 16 24 32 40

[0063] Detect the concentration of halogen in liquid chloromethane. The specific operation is:

[0064] First, 250 ml of the liquid methyl chloride to be tested is placed in an environment below 40°C to evaporate until the liquid volume is less than 5 ml. The mixture is then transferred to a 250 ml volumetric flask and diluted to the mark with water to prepare test solution A.

[0065] Then, take 20 ml of test solution A in a beaker, add hydrochloric acid with a concentration of (1+10) to the beaker to adjust the pH value to 4.6, then transfer the solution in the beaker to a 100 ml volumetric flask and dilute it to the mark with water, shake well and set aside to prepare test solution B;

[0066] Three groups of test solution B were placed in three 25 ml colorimetric tubes, respectively. The volume V1 of the first group of test solution B was 1 ml, the volume V2 of the second group of test solution B was 2 ml, and the volume V3 of the third group of test solution B was 5 ml. To each colorimetric tube, 0.5 ml of acetic acid-sodium acetate buffer solution and 0.4 ml of phenol red solution were first added and shaken. Then, 1 ml of chloramine-T solution was added and immediately shaken for 2 minutes. Then, 1 ml of sodium thiosulfate solution was added and shaken for 15 seconds. The colorimetric tubes were diluted to the mark with water, shaken, and allowed to stand for 15 minutes, thereby obtaining three groups of test solutions. The absorbance of each group of test solutions at 590 nm was measured. The absorbance of group 1 was 0.0526, that of group 2 was 0.1061, and that of group 3 was 0.273. The absorbance of each group of test solutions was compared with the absorbance-halogen content standard curve to obtain the halogen content in each group of test solutions; among them, the halogen content X1 of Group 1 was 6.574384ug, the halogen content X2 of Group 2 was 12.959074ug, and the halogen content X3 of Group 3 was 32.87692ug.

[0067] Specifically, the halogen concentration in the liquid methyl chloride to be tested is obtained from the first set of data as X1 / [V1·(W1 / W2)]=32.87192 mg / L;

[0068] Specifically, the halogen concentration in the liquid methyl chloride to be tested is obtained from the second set of data as X2 / [V2·(W1 / W2)]=32.397685 mg / L;

[0069] Specifically, the halogen concentration in the liquid chloromethane to be tested is obtained from the third set of data as X3 / [V3·(W1 / W2)]=32.87692 mg / L;

[0070] The average value is calculated to obtain the halogen concentration in the liquid chloromethane to be tested as (32.87192+32.397685+32.87692) / 3=32.71550833 mg / L.

[0071] For a more intuitive observation, the above data are listed in Table 2.

[0072] Table 2

[0073]

[0074] Detect the spike recovery rate. The specific operation is as follows:

[0075] Take 1 ml of test solution B and place it in a 25 ml colorimetric tube as the blank group, take 3 groups of 1 ml of test solution B and place them in 3 25 ml colorimetric tubes as the control group, add a halogen standard solution with a mass concentration of 4 ug / ml to the 3 control groups respectively, and do not add a halogen standard solution to the blank group; among them, the volume U1 of the halogen standard solution added to the first control group is 1 ml, the volume U2 of the halogen standard solution added to the second control group is 2 ml, and the volume U3 of the halogen standard solution added to the third control group is 3 ml.

[0076] To the colorimetric tube of the blank group and each control group, respectively, 0.5 ml of acetic acid-sodium acetate buffer solution and 0.4 ml of phenol red solution were added and shaken, then 1 ml of chloramine-T solution was added and immediately shaken for 2 minutes, then 1 ml of sodium thiosulfate solution was added and shaken for 15 seconds, and then diluted with water to the scale of the colorimetric tube, shaken and allowed to stand for 15 minutes, and then the absorbance of the blank group solution and the three control group solutions at 590 nm was measured respectively; the absorbance of the blank group was 0.0524, the absorbance of the first control group was 0.086, the absorbance of the second control group was 0.1195, and the absorbance of the third control group was 0.1529.

[0077] The absorbance of the blank solution was compared with the absorbance-halogen content standard curve, and the halogen content Y0 in the blank solution was 6.5505ug;

[0078] The absorbance of the three control groups was compared with the absorbance-halogen content standard curve. The halogen content Y1 in the first control group solution was 10.5603 ug, the halogen content Y2 in the second control group solution was 14.5582 ug, and the halogen content Y3 in the third control group solution was 18.5442 ug.

[0079] The spiked recovery of the first control group was calculated as P1 = [(Y1 - Y0) / (U1·C)] × 100% = 100.25%;

[0080] The spiked recovery rate of the second control group was calculated as P2 = [(Y2 - Y0) / (U2·C)] × 100% = 100.1%;

[0081] The spiked recovery rate of the third control group was calculated as P3 = [(Y3 - Y0) / (U3·C)] × 100% = 99.95%.

[0082] It can be seen that the spiked recoveries are between 95% and 105%, proving that the results of this method are accurate and feasible.

[0083] For a more intuitive observation, the above data are listed in Table 3.

[0084] Table 3

[0085]

[0086] In summary, the halogen concentration in test solution A can be obtained according to the formula Xi / [Vi·(W1 / W2)]. Since test solution A is obtained by diluting the liquid methyl chloride to its original volume after evaporation of the liquid methyl chloride, the halogen concentration in test solution A is the same as the halogen concentration in the liquid methyl chloride to be tested. Therefore, the halogen concentration in the liquid methyl chloride to be tested can be obtained by averaging the halogen concentrations in multiple test solutions A, thereby accurately detecting the halogen concentration in the liquid methyl chloride.

[0087] The specific embodiments described above further illustrate the technical problems, technical solutions and beneficial effects solved by the present invention. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for detecting halogen concentration in liquid chloromethane, characterized in that: The steps of the method include: S1: Prepare acetic acid-sodium acetate buffer solution, phenol red solution, chloramine-T solution and sodium thiosulfate solution for use, and volatilize a fixed volume of the liquid chloromethane to be tested at room temperature, then dilute with water to the original volume to prepare test solution A, take a volume of W1 of test solution A and add hydrochloric acid to adjust the pH value to 4.4-5, then dilute with water to a volume of W2 and shake well to prepare test solution B; S2: Take N groups of test solution B, wherein the volume of the i-th group of test solution B is Vi, 1≤i≤N, N≥1, and first add acetic acid-sodium acetate buffer solution with a volume of K1 and phenol red solution with a volume of K2 to each group of test solution B and shake up, then add chloramine-T solution with a volume of K3 and shake up, then add sodium thiosulfate solution with a volume of K4 and shake up, then dilute with water to a volume of W0 and shake up and let stand to obtain N groups of test solutions, respectively measure the absorbance of each group of test solutions at a wavelength λ, and compare the absorbance of each group of test solutions with the drawn absorbance-halogen content standard curve to obtain the halogen content in each group of test solutions, wherein the halogen content in the i-th group of test solutions is recorded as Xi; S3: The concentration of halogen in the liquid chloromethane to be tested is obtained as ; Among them, the method for drawing the absorbance-halogen content standard curve is: taking multiple groups of halogen standard solutions with different volumes and a mass concentration of C as samples, obtaining the halogen content in each group of samples according to the volume and mass concentration C of the halogen standard solution in each group of samples, first adding a volume of K1 of acetic acid-sodium acetate buffer solution and a volume of K2 of phenol red solution to each group of samples and shaking them well, then adding a volume of K3 of chloramine-T solution and shaking them well, then adding a volume of K4 of sodium thiosulfate solution and shaking them well, then diluting with water to a volume of W0 and shaking and standing, then measuring the absorbance of each group of samples at a wavelength λ, and drawing an absorbance-halogen content standard curve according to the absorbance of each group of samples and the halogen content in each group of samples.

2. The method for detecting the halogen concentration in liquid chloromethane according to claim 1, wherein: The method also includes the following steps: S4: Take a volume of W3 of test solution B as the blank group, take a volume of W3 of test solution B in group M as the control group, add a halogen standard solution with a mass concentration of C to the control group in group M, and do not add a halogen standard solution to the blank group; wherein, the volume of the halogen standard solution added to the j-th control group is Uj, 1≤j≤M, M≥1; To the blank group and each control group, respectively, add a volume of K1 of acetic acid-sodium acetate buffer solution and a volume of K2 of phenol red solution and shake well, then add a volume of K3 of chloramine-T solution and shake well, then add a volume of K4 of sodium thiosulfate solution and shake well, then dilute with water to a volume of W0 and shake well and let stand, then measure the absorbance of the blank group solution and each control group solution at wavelength λ, and compare the absorbance of the blank group solution with the absorbance-halogen content standard curve to obtain the halogen content Y0 in the blank group solution, and compare the absorbance of each group of control group solutions with the absorbance-halogen content standard curve to obtain the halogen content in each group of control group solutions; wherein, the halogen content in the jth group of control group solutions is recorded as Yj; Obtain the spiked recovery rate of each control group; where the spiked recovery rate of the j-th control group Pj = [(Yj-Y0) / (Uj·C)] × 100%.

3. The method for detecting the halogen concentration in liquid chloromethane according to claim 2, wherein: K1 is 0.5 ml, K2 is 0.4 ml, K3 is 1 ml, K4 is 1 ml, W0 is 25 ml, wavelength λ is 590 nm, and mass concentration C is 4 ug / ml; The specific operations of step S4 are: Take a volume of W3 of test solution B and place it in a 25ml colorimetric tube as the blank group. Take a volume of W3 of test solution B in group M and place it in a 25ml colorimetric tube as the control group. Add a halogen standard solution with a mass concentration of 4ug / ml to the control group in group M, while do not add a halogen standard solution to the blank group. Among them, the volume of the halogen standard solution added to the control group in group j is Uj; To the colorimetric tube of the blank group and the colorimetric tube of each control group, respectively, 0.5 ml of acetic acid-sodium acetate buffer solution and 0.4 ml of phenol red solution were first added and shaken, then 1 ml of chloramine-T solution was added and immediately shaken for 2 minutes, then 1 ml of sodium thiosulfate solution was added and shaken for 15 seconds, and then diluted with water to the scale of the colorimetric tube, shaken and allowed to stand for 15 minutes, and then the absorbance of the blank group solution and each control group solution at 590 nm was measured respectively, and the halogen content Y0 in the blank group solution was obtained by comparing the absorbance of the blank group solution with the absorbance-halogen content standard curve, and the halogen content in each group of control group solutions was obtained by comparing the absorbance of each group of control group solutions with the absorbance-halogen content standard curve; wherein, the halogen content in the jth group of control group solutions is recorded as Yj; Obtain the spiked recovery rate of each control group; where the spiked recovery rate of the j-th control group Pj = [(Yj-Y0) / (Uj·C)] × 100%.

4. The method for detecting the halogen concentration in liquid methyl chloride according to claim 1, wherein: K1 is 0.5ml, K2 is 0.4ml, K3 is 1ml, K4 is 1ml, W0 is 25ml, and the wavelength λ is 590nm; The specific operation of step S2 is as follows: take N groups of test solutions B and place them in 25 ml colorimetric tubes respectively, wherein the volume of the i-th group of test solution B is Vi, first add 0.5 ml of acetic acid-sodium acetate buffer solution and 0.4 ml of phenol red solution to the test solution B in each colorimetric tube and shake well, then add 1 ml of chloramine-T solution and immediately shake well for 2 minutes, then add 1 ml of sodium thiosulfate solution and shake well for 15 seconds, then add water to the colorimetric tube to dilute to the scale and then shake and stand for 15 minutes, thereby obtaining N groups of test solutions, respectively measuring the absorbance of each group of test solutions at 590 nm, and comparing the absorbance of each group of test solutions with the drawn absorbance-halogen content standard curve to obtain the halogen content in each group of test solutions; wherein the halogen content in the i-th group of test solutions is recorded as Xi.

5. The method for detecting the halogen concentration in liquid chloromethane according to claim 1, wherein: K1 is 0.5 ml, K2 is 0.4 ml, K3 is 1 ml, K4 is 1 ml, W0 is 25 ml, wavelength λ is 590 nm, and mass concentration C is 4 ug / ml; The specific method for drawing the absorbance-halogen content standard curve is as follows: take multiple groups of 4ug / ml halogen standard solutions of different volumes as samples and place them in 25ml colorimetric tubes respectively, obtain the halogen content in each group of samples according to the volume and mass concentration of the halogen standard solution in each group of samples, first add 0.5ml acetic acid-sodium acetate buffer solution and 0.4ml phenol red solution to the sample in each colorimetric tube and shake well, then add 1ml chloramine-T solution and immediately shake well for 2 minutes, then add 1ml sodium thiosulfate solution and shake well for 15 seconds, then add water to the colorimetric tube to dilute to the scale and then shake and let stand for 15 minutes, then measure the absorbance of each group of samples at 590nm, and draw the absorbance-halogen content standard curve according to the absorbance of each group of samples and the halogen content in each group of samples.

6. The method for detecting the halogen concentration in liquid chloromethane according to claim 1, wherein: The specific operation of preparing test solution A in step S1 is as follows: 250 ml of the liquid chloroform to be tested is placed in an environment below 40° C. to evaporate until the liquid volume is less than 5 ml, then transferred to a 250 ml volumetric flask and diluted with water to the scale, thereby preparing test solution A.

7. The method for detecting the halogen concentration in liquid chloromethane according to claim 1, wherein: W1 is 20ml, W2 is 100ml; The specific operation of preparing test solution B in step S1 is as follows: take 20 ml of test solution A into a beaker, add hydrochloric acid to the beaker to adjust the pH value to 4.6, then transfer the solution in the beaker to a 100 ml volumetric flask, dilute it with water to the scale, shake it well and set aside to prepare test solution B.

8. The method for detecting the halogen concentration in liquid methyl chloride according to claim 1, wherein: Step S1 also includes: preparing a halogen standard solution with a mass concentration of C for standby use.

9. The method for detecting the halogen concentration in liquid chloromethane according to claim 8, wherein: The mass concentration C is 4ug / ml. The steps for preparing a halogen standard solution with a mass concentration of 4ug / ml are: Prepare 0.1 mg / ml halogen standard solution and store in a brown bottle; Pipette 4 ml of 0.1 mg / ml halogen standard solution into a 100 ml brown volumetric flask and dilute to the mark with water to obtain a 4 ug / ml halogen standard solution.

10. The method for detecting the halogen concentration in liquid chloromethane according to claim 1, wherein: In step S1, the pH value of the prepared acetic acid-sodium acetate buffer solution is 4.6, the concentration of the prepared phenol red solution is 0.24 g / L, the concentration of the prepared chloramine-T solution is 2 g / L, and the concentration of the prepared sodium thiosulfate solution is 2.5 g / L.

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