CN115236066A - Detection technology of sulfur dioxide content in samples - Google Patents

Abstract

Provided is a process for detecting sulfur dioxide content in a sample, comprising the following steps: heating a distillate and a sample in the distillate and making the distillate completely boil; applying nitrogen gas to the distillate; the nitrogen carrying sulfur dioxide and water The steam enters the first and second condenser tubes in series and is led into the absorption liquid; standard alkali is titrated to the absorption liquid and the content of sulfur dioxide in the sample is calculated. The process is equipped with two-stage condensation, which improves the separation and removal efficiency of water vapor, avoids the interference and influence of water vapor on subsequent titration detection, improves the detection accuracy of sulfur dioxide content, and at the same time, complete boiling speeds up the volatilization speed of sulfur dioxide, improving the detection efficiency. At the same time of distillation, standard lye can be automatically titrated to realize complete detection automation.

Description

Detection technology of sulfur dioxide content in samples

technical field

The invention relates to the field of detection of sulfur dioxide residues in foods and medicines, in particular to a detection process for the content of sulfur dioxide in a sample.

Background technique

The safety and health of food and medicinal materials has been paid more and more attention. Among them, the content of sulfur dioxide in edible and medicinal materials needs to be specially 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, so that the sulfur dioxide gas is distilled out of the liquid surface, and the sulfur dioxide gas is pushed into the condensation tube through nitrogen, and the condensation tube produces the distillation result. The water vapor condensed and returned to the test tube, and the sulfur dioxide was pushed to the collection container by nitrogen gas, such as the reaction cup, and absorbed by the absorbing liquid with the color developer, so as to realize the collection of sulfur dioxide, and then manually titrated by the testing personnel. For example, the existing national food sulfur dioxide detection standard stipulates that heating and distillation of the sample needs to maintain the "slightly boiling" state of the distillate (such as hydrochloric acid solution), and the distillation time is 90-120 minutes. However, the state of "slight boiling" is difficult to standardize and control, the distillation time is long and the efficiency is low, the collected gas composition and content are difficult to precisely control, and if the degree of boiling is greater than "slight boiling", too much water in distilled water may be produced. Randomly (the pipe has an adsorption effect on the liquid, and it will flow down if it is too much) into the reaction cup, and the distilled water is dissolved in sulfur dioxide, which may be the inflow of the residual distilled water from the previous sample, resulting in great cross-interference. The results of subsequent manual titration tests are also very error-prone.

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

SUMMARY OF THE INVENTION

In order to solve the above-mentioned at least one technical problem, the applicant has found through research that the water vapor from the distillate in the prior art is often entrained into the reaction cup along with nitrogen and sulfur dioxide, thereby diluting the color of the color developer in the reaction cup. During titration detection, the judgment of the end point of acid-base balance will drift and cause errors. To this end, according to an aspect of the present invention, there is provided a detection process for the content of sulfur dioxide in a sample, characterized in that it includes:

heating the distillate and the sample in the distillate and bringing the distillate to a complete boil;

applying nitrogen to the distillate;

The nitrogen carries sulfur dioxide and water vapor into the first condenser tube and the second condenser tube in series and is introduced into the absorption liquid;

A standard base was titrated to the absorption solution and the content of sulfur dioxide in the sample was calculated.

According to another aspect of the present invention, it is judged that the distillation of sulfur dioxide in the sample is complete according to the time for heating the distillate, which is a first predetermined time, and the first predetermined time is 5-60 minutes.

According to another aspect of the present invention, it is judged that the sulfur dioxide in the sample is completely distilled according to the time when the distillate is completely boiled, and the time is a first predetermined time, and the first predetermined time is 5-40 minutes.

According to yet another aspect of the present invention, the titration acid-base balance point is automatically determined by the light-emitting unit disposed on the first side of the cuvette and the color sensor located on the second side of the cuvette.

According to yet another aspect of the present invention, a color frame is drawn according to the real-time color of the color indicator in the absorption liquid, and the real-time recorded standard alkali droplet titration speed is drawn into a bar graph, which is displayed on a display.

According to another aspect of the present invention, in the titration process, the titration speed of the standard alkali solution is controlled from fast to slow, and the interval time between slow drops gradually becomes longer, until there is no titration per unit time, and when there is no titration per unit time, it is judged that the sulfur dioxide in the sample is distilled completely.

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

According to yet another aspect of the present invention, the first predetermined time decreases as the boiling severity of the distillate increases.

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

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

The present invention can obtain one or more of the following technical effects:

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

Two-stage condensation is provided, which avoids the interference and influence of water vapor on subsequent titration detection, and improves the detection accuracy of sulfur dioxide content;

The complete boiling of the distillate can speed up the volatilization speed of sulfur dioxide, improve the detection efficiency, and shorten the complete extraction time of sulfur dioxide to between 5-60 minutes, including automatic titration and calculation of sulfur dioxide content;

The combination of complete boiling and two-stage condensation further realizes the efficient removal of water vapor and greatly improves the detection efficiency, while reducing the detection error.

Description of drawings

The present invention will be described in further detail below with reference to the accompanying drawings and specific embodiments.

Fig. 1 is a process flow diagram of sulfur dioxide detection according to a preferred embodiment of the present invention.

FIG. 2 is a schematic structural diagram of a sulfur dioxide detector according to a preferred embodiment of the present invention.

3 is a schematic structural diagram of an acid-base balance point automatic determination unit according to a preferred embodiment of the present invention.

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

Fig. 5 is a schematic structural diagram of a first condenser pipe according to a preferred embodiment of the present invention.

Detailed ways

Below in conjunction with the accompanying drawings, the best mode of implementation of the present invention will be described through preferred embodiments. The specific embodiments herein are intended to describe the present invention in detail, and should not be construed as a limitation to the present invention, without departing from the spirit and essence of the present invention. Various deformations and modifications can be made within the scope of the present invention, and these should be included within the protection scope of the present invention.

Example 1

According to a preferred embodiment of the present invention, referring to FIG. 1 , a process for detecting sulfur dioxide content in a sample is provided, which is characterized by comprising:

heating the distillate and the sample in the distillate and bringing the distillate to a complete boil;

applying nitrogen to the distillate;

The nitrogen carries sulfur dioxide and water vapor into the first condenser tube and the second condenser tube in series and is introduced into the absorption liquid;

A standard base was titrated to the absorption solution and the content of sulfur dioxide in the sample was calculated.

Preferably, the first condensing tube condenses a large part of the water vapor and flows back into the test tube. The second condenser tube condenses the remaining water vapor to obtain a mixed gas of sulfur dioxide and nitrogen.

Preferably, the standard alkali is titrated to the absorption liquid until the acid-base equilibrium point, and as the sulfur dioxide enters the reaction cup, the standard alkali is subsequently titrated, and the distillation is repeated until the end of the distillation. Calculate the content of sulfur dioxide in the sample based on the consumption of standard alkali volume.

Further, since water has the ability to absorb sulfur dioxide, the generated water vapor is separated from it as much as possible after distillation. If there is an uncertain amount of water (the pipe has an adsorption effect on the liquid, and the liquid dripping into the reaction cup is a random state) into 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), detect Data can be inaccurate. Since the amount of sulfur dioxide in the sample is very small, usually on the order of milligrams, any possible interference will produce large errors.

Further, in the Pharmacopoeia and the national food standard, the liquid in the test tube is required to be in a "slightly boiling" state, the purpose is to generate as little water vapor as possible, and it can be cooled by the condenser and returned to the test tube. Since this "slight boiling" is not precisely defined and quantified, adjusting the "slightly boiling" state brings uncertainty to the detection. What's more, even if there is no heating, the "slightly boiling" state will be seen by the naked eye when nitrogen is charged into the sample liquid, which may cause the sample to appear in a false "slightly boiling" state for detection without reaching the temperature. It makes the sulfur dioxide gas not easy to be distilled out, even if it is not possible to obtain reliable data through long-term distillation (90-120 minutes).

Preferably, a stepper motor is used to automatically titrate the standard lye. For example, a standard base with a concentration of 0.01 mol/L can be used. It is understandable that the naked eye has a large error in judging the end point of acid-base balance, and the minimum titration volume of manual titration is 50-80 μl. In contrast, the minimum titration volume for automatic titration with a stepper motor is only 10 μl.

According to another preferred embodiment of the present invention, the complete distillation of sulfur dioxide in the sample is determined according to the time for heating the distillate, which is a first predetermined time, and the first predetermined time is 5-60 minutes.

According to another preferred embodiment of the present invention, it is judged that the distillation of sulfur dioxide in the sample is complete according to the time when the distillate is completely boiled, and the time is a first predetermined time, and the first predetermined time is 5-40 minutes.

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

According to yet another preferred embodiment of the present invention, referring to FIG. 4 , a color frame is drawn according to the real-time color of the color indicator in the absorption liquid, and the real-time recorded standard alkali liquid titration speed is drawn into a bar graph, which is displayed on the display, that is, the display Sulfur dioxide distillation-titration diagram.

Further, due to the heavy weight of sulfur dioxide gas, it is very important to monitor the state of sulfur dioxide being distilled and whether the titration is at the equilibrium point. Therefore, a sulfur dioxide distillation-titration chart is designed. After the sulfur dioxide is pushed into the absorption liquid for a predetermined time, such as one minute, start the titration (ie, simultaneous distillation and titration), record the titration volume per unit time, and a large amount of sulfur dioxide gas is absorbed in the early stage. To the acid-base equilibrium point, repeated titration-detection, as a large amount of sulfur dioxide is absorbed, the amount of distilled sulfur dioxide gradually decreases, the titration solution becomes very slow, and the interval becomes longer. According to this, it can be judged that the sulfur dioxide was almost completely distilled at the last time. At the same time, draw the acid-base point in the reaction cup into an equilibrium curve to determine whether the end point of the titration is at the equilibrium point.

According to another preferred embodiment of the present invention, in the titration process, the titration speed of the standard alkali solution is controlled from fast to slow, and the interval between slow drops gradually becomes longer until there is no titration per unit time. Distillation of sulfur dioxide is complete. More specifically, the titration speed of the control standard lye in the titration process 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 volume per unit time will be small, and if no sulfur dioxide is distilled out per unit time, it will not be titrated. And the slow titration interval gradually becomes longer, and when there is no titration within the second predetermined time, it can be judged that the sulfur dioxide in the sample is completely distilled.

According to another preferred embodiment of the present invention, 5-30 seconds before the end of distillation, a predetermined amount of absorbing liquid is added to the reaction cup. Further, since the amount of nitrogen passing through the narrow pipe to the reaction cup will have a great impact on the absorption liquid, it is possible that the entrained sulfur dioxide will flush out of the absorption liquid, and the cross-sectional area of the reaction cup is very large, and the thrust of the nitrogen gas almost disappears and is flushed out. The nitrogen gas is absorbed by the liquid on the cuvette wall or floats on the liquid surface. In the present invention, 5-30 seconds before the end of distillation, a quantitative absorption liquid is added in the reaction cup, the two are absorbed through the absorption liquid, and the distillation-titration is continued to acid-base balance, thereby further improving the accuracy of detection data.

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

According to yet another preferred embodiment of the present invention, the flow rate of nitrogen applied to the distillate is 1-2.5 liters per minute. Due to the heavy weight of sulfur dioxide gas, the entire process needs to be assisted by nitrogen. The flow rate of nitrogen is also an important parameter. If it is too small, it cannot generate enough thrust, and the sulfur dioxide gas cannot be completely absorbed. If it is too large, it may cause the distilled water to quickly pass through the condenser and not be sufficiently cooled, increasing the probability of water vapor entering the reaction cup. Nitrogen gas coming out of the reaction cup will be wrapped in sulfur dioxide before it can be absorbed by the absorption liquid and flushed out of the absorption liquid.

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

The present invention can obtain one or more of the following technical effects:

It can realize automatic real-time detection of sulfur dioxide content in samples and reduce the workload of testing personnel;

Two-stage condensation is provided, which avoids the interference and influence of water vapor on subsequent titration detection, and improves the detection accuracy of sulfur dioxide content;

The complete boiling of the distillate can speed up the volatilization rate of sulfur dioxide and improve the detection efficiency, including automatic addition of hydrochloric acid, absorption liquid, distillation, titration, titration end point judgment, calculation results, etc. And can prompt: Is the sulfur dioxide in the sample distilled completely? Is the titration at equilibrium? Eliminate the generation of erroneous data, which can shorten the complete extraction time of sulfur dioxide to between 5-60 minutes, including automatic titration and calculation of sulfur dioxide content;

The combination of complete boiling and two-stage condensation further realizes the efficient removal of water vapor and greatly improves the detection efficiency, while reducing the detection error.

Example 2

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

Test tubes for holding distillates and samples;

a steam generator for generating steam and heating the distillate and the sample by the steam, keeping the distillate fully boiling;

Nitrogen generator for generating nitrogen and applying it to the test tube;

a first condenser tube, communicated with the test tube, and nitrogen carrying sulfur dioxide and water vapor enters the first condenser tube from the test tube;

a second condensing pipe, connected in series with the first condensing pipe;

a reaction cup containing an absorption liquid and a color indicator into which nitrogen and sulfur dioxide from the second condenser are passed; and

The titration unit is used for titrating standard alkali to the absorption liquid and calculating the content of sulfur dioxide in the sample.

According to another preferred embodiment of the present invention, the sulfur dioxide detector further includes a distillation end determination unit for determining that the sulfur dioxide in the sample is completely distilled.

According to another preferred embodiment of the present invention, the distillation end determination unit determines the end of distillation according to the working time of the steam generator, where the working time 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.

According to another preferred embodiment of the present invention, the sulfur dioxide detector further includes an acid-base balance point automatic judging unit, and the acid-base balance point automatic judging unit includes a light-emitting unit disposed on the first side of the cuvette and a light-emitting unit located on the first side of the cuvette. Color sensor on both sides.

Preferably, the color change of the color indicator can be detected by a color sensor, and the detected data is sent to the processor in real time, and the processor accepts and stores the real-time color change and processes it, and the detected color starts from red to the end of the titration. is yellow, the titration is over. The color-developing agent is methyl red, which is red in acid and yellow in alkali. The hydrogen peroxide is weakly acidic and appears red. After the sulfur dioxide is absorbed, it continues to appear red. With the distillation, the standard alkali titration also begins. With the titration of the alkali, the inside of the reaction cup is yellow. balance point.

According to another preferred embodiment of the present invention, the sulfur dioxide detector further includes a distillation atlas unit, which is used to draw a color frame according to the real-time color of the color indicator, and draw the real-time recorded standard alkali titration speed into a histogram, through the display is displayed. Detectors can monitor the detection process and whether the final data is abnormal through the distillation map.

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 interval time between slow drops gradually becomes longer until there is no titration per unit time; The distillation end judgment unit judges that the distillation of sulfur dioxide in the sample is complete according to no titration per unit time.

According to another preferred embodiment of the present invention, a drain valve is communicated with the bottom of the reaction cup.

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

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

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

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

Preferably, the light-emitting unit is a compound light spectrum lamp.

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

According to yet another preferred embodiment of the present invention, the parts of the cuvette corresponding to the light-emitting unit and the color sensor are composed of optical glass.

According to yet another preferred embodiment of the present invention, the steam from the steam generator is led to the bottom of the distillate through a pipeline.

According to yet another preferred embodiment of the present invention, the nitrogen gas from the nitrogen generator is led to the bottom of the distillate through piping.

According to yet another preferred embodiment of the present invention, referring to FIG. 5 , the first condensation pipe includes:

a body 2 comprising two or more expansion parts 22 and a neck 21 connected between adjacent expansion parts 22 and having a mixed gas inlet 23 at a first end and a mixed gas outlet 24 at a second end; and

The spoiler pipe 3 is arranged at the mixed gas outlet 24, and the first end 31 extends into the expansion part adjacent to the mixed gas outlet, and the second end 32 extends out of the mixed gas outlet;

The body 2 is surrounded by cooling liquid, and the portion of the spoiler tube 3 extending into the expansion portion is composed of a vertical portion and a bent portion that are connected in sequence.

According to another preferred embodiment of the present invention, the body 2 is arranged vertically with the mixed gas inlet 23 at the bottom, the mixed gas outlet 24 at the top, and the opening at the first end 31 of the spoiler pipe faces to one side . Advantageously, the first end of the spoiler pipe extends into the expansion part adjacent to the outlet of the mixed gas, which prevents the gas from directly passing through the outlet, changes, disturbs and increases the path of the airflow, and increases the number of times that the water vapor hits the inner wall of the body. , further improving the condensation efficiency.

The working principle of the present invention is as follows: the sample is placed in a test tube (test tube), diluted hydrochloric acid is added, and the sample is heated and distilled to allow the sulfur dioxide gas to be distilled out of the liquid surface. Pass nitrogen. The nitrogen action pushes the sulfur dioxide gas into the condenser tube, the condenser tube condenses the water vapor produced by distillation and returns it to the test tube, and the sulfur dioxide is pushed into the reaction cup by the nitrogen gas and absorbed by the absorbing liquid with the color developer. Then, titrate the absorption titration of absorbing sulfur dioxide by standard alkali, determine the acid-base balance point by the color change of the color developer, and finally calculate the content of sulfur dioxide in the sample by the volume of standard alkali consumed.

Example 3

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

1. Reagents and Materials

1.1 Reagents

1.1.1 Hydrogen peroxide (H2O2): 30%.

1.1.2 Absolute ethanol (C2H5OH).

1.1.3 Sodium hydroxide (NaOH).

1.1.4 Methyl red (C15H15N3O2).

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

1.1.6 High-purity nitrogen.

1.1.7 Sodium sulfite (Na2SO3)

1.2 Reagent configuration

1.2.1 Hydrogen peroxide solution (3%): Measure 100 mL of hydrogen peroxide with a mass fraction of 30%, add water to dilute to 1000 mL. Ready for temporary use.

1.2.2 Hydrochloric acid solution (0.3mol/L): Measure 125mL of hydrochloric acid (ρ20=1.19g/mL), slowly pour it into 4500mL of water, add while stirring, and continue to add water to dilute to 5000mL.

1.2.3 Methyl red ethanol solution indicator (2.5g/L): Weigh 0.25 g of methyl red indicator and dissolve it in 100 mL of absolute ethanol. After fully dissolving, take 3mL indicator to 1.2.1.

1.3 Standard solution

Sodium hydroxide standard solution (0.01mol/L): a standard titration solution prepared and calibrated according to GB/T 601 or certified by the state and granted a certificate of reference material.

2 Test Conditions

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

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

2.3 Distillation power: 450W.

2.4 Distillation time: 15 minutes.

2.5 Nitrogen: 1.5 L/min.

2.6 Sodium sulfite solution: take 1 mL of solution 1 and 1 mL of solution 2.

3 Test results

The present invention can obtain one or more of the following technical effects:

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

Two-stage condensation is provided, which avoids the interference and influence of water vapor on subsequent titration detection, and improves the detection accuracy of sulfur dioxide content;

The complete boiling of the distillate can speed up the volatilization speed of sulfur dioxide, improve the detection efficiency, and shorten the complete extraction time of sulfur dioxide to between 5-60 minutes, including automatic titration and calculation of sulfur dioxide content;

The combination of complete boiling and two-stage condensation further realizes the efficient removal of water vapor and greatly improves the detection efficiency, while reducing the detection error.

Those skilled in the art should understand that the present invention is not limited by the above-mentioned embodiments, and the descriptions in the above-mentioned embodiments and the description are only to illustrate 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 modifications fall within the scope of the claimed invention. The claimed scope of the present invention is defined by the appended claims and their equivalents.

Claims (10)

1. the detection technique of sulfur dioxide content in a sample is characterized in that comprising the following steps: heating the distillate and the sample in the distillate and bringing the distillate to a complete boil; applying nitrogen to the distillate; The nitrogen carries sulfur dioxide and water vapor into the first condenser tube and the second condenser tube in series and is introduced into the absorption liquid; A standard base was titrated to the absorption solution and the content of sulfur dioxide in the sample was calculated. 2. the detection technique of sulfur dioxide content in the sample according to claim 1, is characterized in that according to the time of heating distillate to judge that the sulfur dioxide distillation in the sample is complete, and described time is the first predetermined time, and described first predetermined time 5-60 minutes. 3. the detection technique of sulfur dioxide content in the sample according to claim 1, it is characterized in that according to the time when described distillate fully boils, judge that the sulfur dioxide distillation in the sample is complete, and described time is the first predetermined time, the described second A predetermined time is 5-40 minutes. 4. The detection process of sulfur dioxide content in the sample according to any one of claims 1-3, characterized in that the titration is automatically determined by the light-emitting unit arranged on the first side of the reaction cup and the color sensor positioned on the second side of the reaction cup acid-base balance. 5. the detection technique of sulfur dioxide content in the sample according to claim 4, it is characterized in that according to the real-time color of the color indicator in the absorption liquid to draw a color frame, and the standard alkali titration speed recorded in real time is drawn into a histogram, displayed on the display. 6. the detection technique of sulfur dioxide content in the sample according to claim 1, it is characterized in that in the titration process, the titration speed of control standard alkali liquor is from fast to slow, and the slow drip interval time gradually becomes longer, until there is no titration in unit time, When there is no titration per unit time, it is judged that the sulfur dioxide in the sample is completely distilled. 7 . The detection process of sulfur dioxide content in a sample according to claim 4 , wherein a predetermined amount of absorbing liquid is added to the reaction cup 5-30 seconds before the end of distillation. 8 . 8 . The method for detecting sulfur dioxide content in a sample according to claim 4 , wherein the first predetermined time decreases as the boiling intensity of the distillate increases. 9 . 9. The method for detecting sulfur dioxide content in a sample according to claim 4, wherein the flow rate of nitrogen gas applied to the distillate is 1-2.5 liters per minute. 10 . The method for detecting sulfur dioxide content in a sample according to claim 8 , wherein the first predetermined time is 10-20 minutes. 11 .

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