Detection Process for Sulfur Dioxide Content in Samples

Abstract

A detection process for the sulfur dioxide content in a sample is provided, including the following steps: heating the distillate and the sample in the distillate and bringing the distillate to a complete boil; applying nitrogen gas into the distillate; the nitrogen gas carrying sulfur dioxide and water vapor enters a series-connected first condenser and second condenser and is introduced into the absorption liquid; titrating the standard alkali solution to the absorption liquid and calculating the sulfur dioxide content in the sample. This process is provided with two-stage condensation, which improves the separation and removal efficiency of water vapor, avoids the interference and influence of water vapor on the subsequent titration detection, improves the detection accuracy of the sulfur dioxide content, and at the same time the complete boiling speeds up the volatilization rate of sulfur dioxide, improving the detection efficiency. During distillation, the standard alkali solution can be automatically titrated, realizing complete detection automation.

Description

Technical Field

[0001] The present invention relates to the field of detecting sulfur dioxide residues in foods and drugs, and particularly to a detection process for the sulfur dioxide content in a sample. Background Art

[0002] The safety and health of food and medicinal materials have been increasingly emphasized. Among them, the sulfur dioxide content in food and medicinal materials needs to be specifically detected. In the prior art, the sample to be detected is placed in a test tube, diluted hydrochloric acid is added, and the sample is heated and distilled. The sulfur dioxide gas is distilled out of the liquid surface and is pushed into a condenser by nitrogen. The condenser condenses the water vapor generated by the distillation and returns it to the test tube, while the sulfur dioxide is pushed by nitrogen into a collection container such as a reaction cup and is absorbed by an absorbent solution added with a color reagent, thereby realizing the collection of sulfur dioxide, and then manually titrated by a tester. For example, in the existing national food sulfur dioxide detection standard, it is stipulated that when heating and distilling the sample, the distillate (such as hydrochloric acid solution) needs to be kept in a "gentle boiling" state, and the distillation time is 90 - 120 minutes. However, the "gentle boiling" state is difficult to standardize and control, the distillation time is long and the efficiency is low, the composition and content of the collected gas are difficult to accurately control, and if the boiling degree is greater than "gentle boiling", too much distilled water may randomly (the pipeline has an adsorption effect on the liquid and will flow down only when accumulated) flow into the reaction cup, and this distilled water is dissolved with sulfur dioxide, and it may be the distilled water remaining from the previous sample that flows in, resulting in great cross-interference. The error of the subsequent manual titration detection result is also very large.

[0003] Therefore, it is necessary to study a detection process for the sulfur dioxide content in a sample to solve one or more of the above technical problems. Summary of the Invention

[0004] To solve at least one of the above technical problems, the applicant has found through research that in the prior art, the water vapor from the distillate often enters the reaction cup together with nitrogen and sulfur dioxide, thus diluting the color of the color reagent in the reaction cup, and the judgment of the acid-base balance end point will drift and cause errors during the titration detection. For this reason, according to one aspect of the present invention, a detection process for the sulfur dioxide content in a sample is provided, which is characterized by including:

[0005] Heating the distillate and the sample in the distillate and making the distillate boil completely;

[0006] Applying nitrogen to the distillate;

[0007] The nitrogen carries sulfur dioxide and water vapor into a series-connected first condenser and second condenser and is introduced into the absorbent solution;

[0008] Titrating the standard alkali solution to the absorbent solution and calculating the sulfur dioxide content in the sample.

[0009] According to another aspect of the present invention, it is determined that the distillation of sulfur dioxide in the sample is complete based on the time for heating the distillate. The time is a first predetermined time, and the first predetermined time is 5 - 60 minutes.

[0010] According to another aspect of the present invention, it is determined that the distillation of sulfur dioxide in the sample is complete based on the time when the distillate boils completely. The time is a first predetermined time, and the first predetermined time is 5 - 40 minutes.

[0011] According to another aspect of the present invention, the acid - base titration equilibrium point is automatically determined by a light - emitting unit disposed on the first side of the reaction cup and a color sensor located on the second side of the reaction cup.

[0012] According to another aspect of the present invention, a color frame is drawn based on the real - time color of the color indicator in the absorption liquid, and the titration speed of the standard alkali solution recorded in real time is plotted as a bar chart and displayed through a display.

[0013] According to another aspect of the present invention, during the titration process, the titration speed of the standard alkali solution is controlled to be from fast to slow, and the slow - drip interval time gradually becomes longer until there is no titration per unit time. When there is no titration per unit time, it is determined that the distillation of sulfur dioxide in the sample is complete.

[0014] According to another aspect of the present invention, 5 - 30 seconds before the end of distillation, a predetermined amount of absorption liquid is added into the reaction cup.

[0015] According to another aspect of the present invention, the first predetermined time decreases as the boiling intensity of the distillate increases.

[0016] According to another aspect of the present invention, the flow rate of nitrogen gas applied to the distillate is 1 - 2.5 liters per minute.

[0017] According to another aspect of the present invention, the first predetermined time is 10 - 20 minutes.

[0018] The present invention can achieve one or more of the following technical effects:

[0019] It can realize the automatic real - time detection of the sulfur dioxide content in the sample, including automatic addition of hydrochloric acid, absorption liquid, distillation, titration, titration end - point judgment, calculation of results, etc. And it can prompt: Whether the sulfur dioxide in the sample is completely distilled? Whether the titration is at the equilibrium point? Eliminate the generation of incorrect data and reduce the workload of the detection personnel;

[0020] Two - stage condensation is provided to avoid the interference and influence of water vapor on the subsequent titration detection, and improve the detection accuracy of the sulfur dioxide content;

[0021] The complete boiling of the distillate can accelerate the volatilization rate of sulfur dioxide, improve the detection efficiency, and shorten the complete extraction time of sulfur dioxide to between 5 and 60 minutes, including realizing automatic titration and calculating the sulfur dioxide content;

[0022] The combination of complete boiling and two-stage condensation further realizes the efficient removal of water vapor and a significant improvement in detection efficiency, while reducing the detection error. Brief Description of the Drawings

[0023] The present invention will be further described in detail below in conjunction with the drawings and specific embodiments.

[0024] Figure 1 It is a process flow chart of a sulfur dioxide detection process according to a preferred embodiment of the present invention.

[0025] Figure 2 It is a schematic structural diagram of a sulfur dioxide detector according to a preferred embodiment of the present invention.

[0026] Figure 3 It is a schematic structural diagram of an automatic acid-base balance judgment unit according to a preferred embodiment of the present invention.

[0027] Figure 4 It is a sulfur dioxide distillation-titration diagram according to a preferred embodiment of the present invention.

[0028] Figure 5 It is a schematic structural diagram of a first condenser according to a preferred embodiment of the present invention. Specific Embodiments

[0029] The best mode of the present invention will be described below in conjunction with the drawings through preferred embodiments. The specific embodiments herein are for explaining the present invention in detail and should not be construed as limiting the present invention. Without departing from the spirit and scope of the present invention, various modifications can be made, and all of them should be included within the protection scope of the present invention.

[0030] Embodiment 1

[0031] According to a preferred embodiment of the present invention, refer to Figure 1 , a detection process for the sulfur dioxide content in a sample is provided, which is characterized by including:

[0032] Heating the distillate and the sample in the distillate and causing the distillate to boil completely;

[0033] Applying nitrogen gas to the distillate;

[0034] The nitrogen gas carries sulfur dioxide and water vapor into the series-connected first condenser and second condenser and is introduced into the absorption liquid;

[0035] Titrate the standard alkali solution into the absorption liquid and calculate the sulfur dioxide content in the sample.

[0036] Preferably, the first condenser condenses most of the water vapor and refluxes it into the test tube. The second condenser condenses the remaining water vapor to obtain a mixed gas of sulfur dioxide and nitrogen.

[0037] Preferably, titrate the standard alkali solution into the absorption liquid until the acid-base equilibrium point. As sulfur dioxide enters the reaction cup, the standard alkali is then titrated repeatedly until the distillation ends. Calculate the sulfur dioxide content in the sample based on the volume of the consumed standard alkali.

[0038] Furthermore, since water has the ability to absorb sulfur dioxide, it is necessary to separate the generated water vapor from it as much as possible after distillation. If an uncertain amount of water (the pipeline has an adsorption effect on the liquid, and the liquid dropped into the reaction cup is in a random state) enters the reaction cup, that is, an uncertain amount of sulfur dioxide may enter the reaction cup (it may also be the residue of the previous sample), the detection data will have errors. Since the sulfur dioxide in the sample is extremely trace, usually in the milligram order, any possible interference will cause significant errors.

[0039] Furthermore, in the pharmacopoeia and national food standards, it is required that the liquid in the test tube be in a "gentle boiling" state, aiming to generate as little water vapor as possible and be cooled by the condenser and refluxed back into the test tube. Since this "gentle boiling" has no exact definition and quantification, adjusting the "gentle boiling" state brings uncertainty to the detection. Moreover, even without heating, when nitrogen is introduced into the sample liquid, a "gentle boiling" state can be seen with the naked eye, which may lead to false "gentle boiling" states during detection without the sample reaching the required temperature. As a result, sulfur dioxide gas is not easily distilled out, and reliable data (90 - 120 minutes) may not be obtained even through long-term distillation.

[0040] Preferably, a stepper motor is used to automatically titrate the standard alkali solution. For example, a standard alkali with a concentration of 0.01 mol / L can be used. It can be understood that the visual judgment of the acid-base equilibrium end point has a large error, and the minimum titration volume for manual titration is 50 - 80 μl. In contrast, the minimum titration volume for automatic titration using a stepper motor is only 10 μl.

[0041] According to another preferred embodiment of the present invention, it is determined whether the sulfur dioxide in the sample is completely distilled based on the heating time of the distillate, and the time is a first predetermined time, and the first predetermined time is 5 - 60 minutes.

[0042] According to another preferred embodiment of the present invention, it is determined whether the sulfur dioxide in the sample is completely distilled based on the time when the distillate is completely boiling, and the time is a first predetermined time, and the first predetermined time is 5 - 40 minutes.

[0043] According to another preferred embodiment of the present invention, the acid-base titration equilibrium point is automatically determined by a light-emitting unit disposed on the first side of the reaction cup and a color sensor located on the second side of the reaction cup. More specifically, the acid-base titration equilibrium point is automatically determined by the light-emitting unit disposed on the first side of the reaction cup and the color sensor located on the second side of the reaction cup through the color change of the color-developing agent in the absorption solution.

[0044] According to another preferred embodiment of the present invention, refer to Figure 4 , a color box is drawn according to the real-time color of the color indicator in the absorption solution, and the titration speed of the standard alkali solution recorded in real time is plotted as a bar chart and displayed on the display, that is, the sulfur dioxide distillation-titration diagram is displayed.

[0045] Furthermore, since sulfur dioxide gas is heavy, it is very important to monitor the distillation state of sulfur dioxide and whether the titration is at the equilibrium point. Therefore, a sulfur dioxide distillation-titration diagram is designed. After sulfur dioxide is pushed into the absorption solution for a predetermined time, for example, one minute, titration begins (i.e., synchronous distillation and titration), and the titration volume per unit time is recorded. In the early stage, a large amount of sulfur dioxide gas is absorbed, and the standard alkali is titrated rapidly, and it is judged at any time whether the titration reaches the acid-base equilibrium point, with repeated titration-detection. As a large amount of sulfur dioxide is absorbed, the amount of sulfur dioxide distilled out gradually decreases, the titrant becomes very slow, and the interval time becomes longer. Based on this, it can be judged that almost all the sulfur dioxide is distilled completely at the final time. At the same time, the acid-base point in the reaction cup is traced into an equilibrium curve to judge whether the titration end point is at the equilibrium point.

[0046] According to another preferred embodiment of the present invention, during the titration process, the titration speed of the standard alkali solution is controlled to be from fast to slow, and the slow-dripping interval time gradually becomes longer until there is no titration per unit time. When there is no titration per unit time, it is judged that the sulfur dioxide in the sample is distilled completely. More specifically, during the titration process, the titration speed of the standard alkali solution is determined by the color in the reaction cup. At the beginning, a large amount of sulfur dioxide is distilled out, and the titration volume per unit time is very large. As the sulfur dioxide in the test tube becomes less and less, the titration amount per unit time will be small. If no sulfur dioxide is distilled out per unit time, there is no titration. And the slow-dripping interval time gradually becomes longer until there is no titration within the second predetermined time, and it can be judged that the sulfur dioxide in the sample is distilled completely.

[0047] According to another preferred embodiment of the present invention, 5 - 30 seconds before the end of distillation, a predetermined amount of absorbent liquid is added into the reaction cup. Further, since the large amount of nitrogen gas flowing through the narrow pipe into the reaction cup will cause a great impact on the absorbent liquid, it is possible that the sulfur dioxide gas carried away will be washed out of the absorbent liquid. However, the cross-sectional area of the reaction cup is large, and the thrust of the nitrogen gas almost disappears. The nitrogen gas washed out is absorbed by the liquid on the wall of the reaction cup or floats on the liquid surface. In the present invention, 5 - 30 seconds before the end of distillation, a quantitative absorbent liquid is added into the reaction cup, and the two are absorbed by the absorbent liquid, and the distillation - titration is continued until the acid - base balance is reached, further improving the accuracy of the detection data.

[0048] According to another preferred embodiment of the present invention, the first predetermined time decreases as the boiling intensity of the distillate increases.

[0049] According to another preferred embodiment of the present invention, the flow rate of the nitrogen gas applied to the distillate is 1 - 2.5 liters per minute. Since sulfur dioxide gas is relatively heavy, the assistance of nitrogen gas is required to complete the whole process. The flow rate of nitrogen gas is also a very important parameter. If it is too small, insufficient thrust will be generated and the sulfur dioxide gas cannot be completely absorbed. If it is too large, the distilled water may quickly pass through the condenser tube, unable to be fully cooled, increasing the probability of water vapor entering the reaction cup. The nitrogen gas coming out of the reaction cup will carry sulfur dioxide and rush out of the absorbent liquid before it can be absorbed by the absorbent liquid.

[0050] According to another preferred embodiment of the present invention, the first predetermined time is 10 - 20 minutes.

[0051] The present invention can achieve one or more of the following technical effects:

[0052] It can realize the automatic real - time detection of the sulfur dioxide content in the sample, reducing the workload of the testers;

[0053] Two - stage condensation is provided, avoiding the interference and influence of water vapor on the subsequent titration detection, and improving the detection accuracy of the sulfur dioxide content;

[0054] The complete boiling of the distillate can accelerate the volatilization rate of sulfur dioxide, improving the detection efficiency, including automatic addition of hydrochloric acid, absorbent liquid, distillation, titration, determination of the titration end point, calculation of results, etc. And it can prompt: whether the sulfur dioxide in the sample is completely distilled? Whether the titration is at the equilibrium point? Eliminate the generation of incorrect data, and the complete extraction time of sulfur dioxide can be shortened to between 5 - 60 minutes, including realizing automatic titration and calculating the sulfur dioxide content;

[0055] The combination of complete boiling and two - stage condensation further realizes the efficient removal of water vapor and a significant improvement in detection efficiency, while reducing the detection error.

[0056] Example 2

[0057] According to a preferred embodiment of the present invention, referring to Figure 2-3 , a sulfur dioxide detector is provided, which is characterized by comprising:

[0058] A test tube for accommodating distillate and a sample;

[0059] A steam generator for generating steam and heating the distillate and the sample with the steam to maintain the distillate in a full boil;

[0060] A nitrogen generator for generating nitrogen and applying it into the test tube;

[0061] A first condenser connected to the test tube, and nitrogen carrying sulfur dioxide and water vapor enter the first condenser from the test tube;

[0062] A second condenser connected in series with the first condenser;

[0063] A reaction cup containing an absorbent solution and a color indicator, and nitrogen and sulfur dioxide from the second condenser are introduced into the absorbent solution; and

[0064] A titration unit for titrating a standard alkali solution into the absorbent solution and calculating the content of sulfur dioxide in the sample.

[0065] According to another preferred embodiment of the present invention, the sulfur dioxide detector further comprises a distillation end determination unit for determining whether the sulfur dioxide in the sample has been completely distilled.

[0066] According to another preferred embodiment of the present invention, the distillation end determination unit determines the end of distillation according to the working duration of the steam generator, the working duration is a first predetermined time, and the first predetermined time is 5 - 60 minutes. It can be understood that the first predetermined time can be determined according to experience.

[0067] According to another preferred embodiment of the present invention, the sulfur dioxide detector further comprises an automatic acid-base balance point determination unit, and the automatic acid-base balance point determination unit comprises a light-emitting unit arranged on the first side of the reaction cup and a color sensor located on the second side of the reaction cup.

[0068] Preferably, the color change of the color indicator can be detected by the color sensor, and the detected data is sent to the processor in real time. The processor receives and stores the real-time color change and processes it. The detected color changes from red at the beginning to yellow at the titration end point, then the titration ends. The color-developing agent uses methyl red, which shows red in acidic conditions and yellow in alkaline conditions. Hydrogen peroxide is weakly acidic and shows red. After sulfur dioxide is absorbed, it continues to show red. As the distillation progresses, the standard alkali titration also starts. As the alkali is titrated, the inside of the reaction cup turns yellow. At the end of distillation, it is determined again whether the acid-base balance point is reached.

[0069] According to another preferred embodiment of the present invention, the sulfur dioxide detector further includes a distillation spectrum unit, which is used to draw a color frame based on the real-time color of the color indicator, and draw a bar chart of the titration speed of the standard alkali solution recorded in real time, and display it through a display. The tester can monitor whether the detection process and the final data are abnormal through this distillation spectrum.

[0070] According to another preferred embodiment of the present invention, the sulfur dioxide detector further includes a titration control unit, which is used to control the titration speed of the standard alkali solution from fast to slow, and the slow drip interval time gradually becomes longer until there is no titration per unit time; the distillation end determination unit determines that the sulfur dioxide in the sample is completely distilled according to no titration per unit time.

[0071] According to another preferred embodiment of the present invention, a drain valve is connected to the bottom of the reaction cup.

[0072] According to another preferred embodiment of the present invention, the first predetermined time decreases as the boiling intensity of the distillate increases.

[0073] According to another preferred embodiment of the present invention, the flow rate of the nitrogen gas applied into the test tube is 1 - 2.5 liters per minute.

[0074] According to another preferred embodiment of the present invention, the first predetermined time is 10 - 20 minutes, and the sulfur dioxide detector is a fully automatic sulfur dioxide detector.

[0075] It can be understood that, the same as the prior art, the test tube contains a distillate and a sample to be detected. The distillate is, for example, a hydrochloric acid solution (such as 0.3 mol / L). Measure 150 - 200 mL of hydrochloric acid and slowly pour it into the test tube containing the sample.

[0076] Preferably, the light emitting unit is a composite light spectrum lamp.

[0077] According to another preferred embodiment of the present invention, the absorption liquid is a hydrogen peroxide solution, and the color indicator is a methyl red ethanol solution indicator.

[0078] According to another preferred embodiment of the present invention, the part of the reaction cup corresponding to the light emitting unit and the color sensor is made of optical glass.

[0079] According to another preferred embodiment of the present invention, the water vapor from the water vapor generator is guided to the bottom of the distillate through a pipeline.

[0080] According to another preferred embodiment of the present invention, the nitrogen gas from the nitrogen gas generator is guided to the bottom of the distillate through a pipeline.

[0081] According to another preferred embodiment of the present invention, see Figure 5 , the first condenser includes:

[0082] The main body 2 includes two or more expansion parts 22 and a neck 21 connected between adjacent expansion parts 22, and has a mixed gas inlet 23 at the first end and a mixed gas outlet 24 at the second end; and

[0083] The spoiler tube 3 is arranged at the mixed gas outlet 24, with the first end 31 extending into the expansion part adjacent to the mixed gas outlet, and the second end 32 extending out of the mixed gas outlet;

[0084] Wherein, the main body 2 is surrounded by coolant, and the part of the spoiler tube 3 extending into the expansion part is composed of a vertical part and a bent part connected in sequence.

[0085] According to another preferred embodiment of the present invention, the main body 2 is vertically arranged with the mixed gas inlet 23 at the bottom and the mixed gas outlet 24 at the top, and the opening at the first end 31 of the spoiler tube faces one side. Advantageously, the first end of the spoiler tube extends into the expansion part adjacent to the mixed gas outlet, avoiding the direct passage of gas through the outlet, changing, disturbing and increasing the gas flow path, increasing the number of times of water vapor hitting the inner wall of the main body, and further improving the condensation efficiency.

[0086] The working principle of the present invention is as follows: Place the sample in a test tube, add diluted hydrochloric acid, heat and distill the sample to distill out sulfur dioxide gas from the liquid surface. Since the molecular weight of sulfur dioxide gas is more than twice that of air, nitrogen needs to be passed through the distillate. The function of nitrogen is to push the sulfur dioxide gas into the condenser. The condenser condenses the water vapor generated by distillation and returns it to the test tube, while the sulfur dioxide is pushed by nitrogen to the reaction cup and absorbed by the absorbent solution added with a color reagent. Then, titrate the absorbent solution that has absorbed sulfur dioxide with a standard base, determine the acid-base equilibrium point through the color change of the color reagent, and finally calculate the sulfur dioxide content of the sample through the volume of the standard base consumed.

[0087] Example 3

[0088] According to another preferred embodiment of the present invention, two batches of samples are detected as follows:

[0089] 1. Reagents and materials

[0090] 1.1 Reagents

[0091] 1.1.1 Hydrogen peroxide (H2O2): 30%.

[0092] 1.1.2 Absolute ethanol (C2H5OH).

[0093] 1.1.3 Sodium hydroxide (NaOH).

[0094] 1.1.4 Methyl Red (C15H15N3O2).

[0095] 1.1.5 Analytical pure hydrochloric acid (HCl): (ρ20 = 1.19 g / mL).

[0096] 1.1.6 High-purity nitrogen.

[0097] 1.1.7 Sodium sulfite (Na2SO3)

[0098] 1.2 Reagent preparation

[0099] 1.2.1 Hydrogen peroxide solution (3%): Measure 100 mL of hydrogen peroxide with a mass fraction of 30%, and dilute it with water to 1000 mL. Prepare it freshly before use.

[0100] 1.2.2 Hydrochloric acid solution (0.3 mol / L): Measure 125 mL of hydrochloric acid (ρ20 = 1.19 g / mL), slowly pour it into 4500 mL of water, stir while adding, and continue to add water to make up the volume to 5000 mL.

[0101] 1.2.3 Methyl Red ethanol solution indicator (2.5 g / L): Weigh 0.25 g of methyl red indicator and dissolve it in 100 mL of anhydrous ethanol. After complete dissolution, take 3 mL of the indicator and add it to 1.2.1.

[0102] 1.3 Standard solution

[0103] Sodium hydroxide standard solution (0.01 mol / L): Prepared and calibrated according to GB / T 601 or a standard titration solution certified by the state and issued with a standard substance certificate.

[0104] 2 Test conditions

[0105] 2.1 Hydrochloric acid solution (0.3 mol / L): 150 mL.

[0106] 2.2 Hydrogen peroxide solution (3%): 80 mL.

[0107] 2.3 Distillation power: 450 W.

[0108] 2.4 Distillation time: 15 minutes.

[0109] 2.5 Nitrogen: 1.5 L / minute.

[0110] 2.6 Sodium sulfite solution: Take 1 mL of solution 1 and 1 mL of solution 2.

[0111] 3 Test results

[0112]

[0113] The present invention can achieve one or more of the following technical effects:

[0114] It can realize the automatic real-time detection of the sulfur dioxide content in the sample, including automatic addition of hydrochloric acid, absorbent solution, distillation, titration, determination of the titration end point, calculation of results, etc. And it can prompt: Is the sulfur dioxide in the sample completely distilled? Is the titration at the equilibrium point? It eliminates the generation of incorrect data and reduces the workload of the testers;

[0115] It is provided with two-stage condensation, which avoids the interference and influence of water vapor on the subsequent titration detection and improves the detection accuracy of the sulfur dioxide content;

[0116] The complete boiling of the distillate can accelerate the volatilization rate of sulfur dioxide, improve the detection efficiency, and shorten the complete extraction time of sulfur dioxide to between 5 and 60 minutes, including realizing automatic titration and calculating the sulfur dioxide content;

[0117] The combination of complete boiling and two-stage condensation further realizes the efficient removal of water vapor and a significant improvement in the detection efficiency, while reducing the detection error.

[0118] Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of the present invention claimed is defined by the appended claims and their equivalents.

Claims

1. A detection process for the sulfur dioxide content in a sample, characterized in that It includes the following steps: Heat the distillate and the sample in the distillate and bring the distillate to a full boil; Apply nitrogen gas to the distillate; The nitrogen gas carries sulfur dioxide and water vapor into the first condenser and the second condenser connected in series, and after primary condensation by the first condenser, it directly undergoes secondary condensation through the second condenser and is introduced into the absorption liquid. The first condenser and the second condenser condense the water vapor generated by distillation and return it to the test tube; Titrate the standard alkali solution to the absorption liquid and calculate the sulfur dioxide content in the sample.

2. The detection process for the sulfur dioxide content in the sample according to claim 1, characterized in that Judge whether the sulfur dioxide in the sample is completely distilled according to the heating time of the distillate. The time is the first predetermined time, and the first predetermined time is 5 - 60 minutes.

3. The detection process for the sulfur dioxide content in the sample according to claim 1, characterized in that Judge whether the sulfur dioxide in the sample is completely distilled according to the time when the distillate is fully boiled. The time is the first predetermined time, and the first predetermined time is 5 - 40 minutes.

4. The detection process for the sulfur dioxide content in the sample according to any one of claims 1-3, characterized in that Automatically determine the acid-base titration equilibrium point through the light-emitting unit arranged on the first side of the reaction cup and the color sensor located on the second side of the reaction cup.

5. The detection process for the sulfur dioxide content in the sample according to claim 4, wherein Draw a color box according to the real-time color of the color indicator in the absorption liquid, and plot the titration speed of the standard alkali solution recorded in real time as a bar chart and display it through the display.

6. The detection process for the sulfur dioxide content in the sample according to claim 1, characterized in that During the titration process, control the titration speed of the standard alkali solution to slow down from fast, and the slow-drop interval time gradually becomes longer until there is no titration per unit time. When there is no titration per unit time, judge that the sulfur dioxide in the sample is completely distilled.

7. The detection process for the sulfur dioxide content in the sample according to claim 4, characterized in that Add a predetermined amount of absorption liquid into the reaction cup 5 - 30 seconds before the end of distillation.

8. The detection process of the sulfur dioxide content in the sample according to claim 2, characterized in that The first predetermined time decreases as the boiling intensity of the distillate increases.

9. The detection process for the sulfur dioxide content in the sample according to claim 4, characterized in that The flow rate of the nitrogen gas applied to the distillate is 1 - 2.5 liters per minute.

10. The detection process for the sulfur dioxide content in the sample according to claim 8, characterized in that The first predetermined time is 10 - 20 minutes.

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