Method for extracting and determining saccharin sodium in sweet gloss oil and method for detecting quality of saccharin sodium

Abstract

The invention relates to a method for extracting and determining saccharin sodium in sweet gloss oil and a method for detecting the quality of the saccharin sodium. According to the extraction separation and detection method for the saccharin sodium in the sweet gloss oil, the content of the saccharin sodium in the sweet gloss oil can be rapidly and accurately determined. The method for detecting the quality of the sodium saccharin raw material (namely sodium saccharin dihydrate) does not need complex pretreatment, and can quickly and accurately judge whether the quality of the sodium saccharin raw material is qualified or not.

Description

Technical Field

[0001] The present invention relates to the field of tobacco, and specifically relates to a method for extracting and determining saccharin sodium in a sweet varnish and a method for detecting the quality of saccharin sodium. Background Art

[0002] In recent years, in order to improve the smoking quality of cigarettes and meet the taste enjoyment of consumers, the tobacco industry has developed sweet tipping papers. The technical method used for such sweet tipping papers is to add saccharin sodium to the last ink, i.e., varnish, and coat the sweet ink on the surface of the tipping paper through gravure printing.

[0003] Varnish is composed of resin and organic solvents (such as ethyl acetate, propyl acetate, etc.). Sweet varnish generally modifies the resin in the varnish to have a certain water-soluble ability and adds sweeteners (such as saccharin sodium, etc.) on the basis of the modified varnish.

[0004] Saccharin sodium, also known as sodium o-benzoylbenzenesulfonimide, is an artificially synthesized non-nutritive sweetener. Saccharin sodium is a white crystalline powder, soluble in water and ethanol, and its sweetness is 300-500 times sweeter than sucrose. Because of its low cost, it is widely used to replace sucrose. When saccharin sodium is heated under acidic conditions, it will produce bitter o-aminobenzenesulfonic acid. By-products such as o-toluenesulfonamide will be generated during the preparation of saccharin sodium, which is a carcinogen; o-toluenesulfonamide will generate insoluble saccharin after oxidation and acid precipitation. If a large amount of saccharin sodium is consumed, it will affect the normal secretion of digestive enzymes in the body, reduce appetite, and a large amount of consumption in a short time will cause a decrease in platelets and acute damage. Each country has strict policies on the restricted use of saccharin sodium, and detecting and analyzing the saccharin sodium content in food has become an important requirement. The key process for controlling the saccharin sodium content in the tipping paper lies in controlling the saccharin sodium content in the varnish. At present, there are many detection methods for the saccharin sodium content in tipping papers on the market, but there is no detection method for the saccharin sodium content in varnish.

[0005] In addition, saccharin sodium dihydrate is a crystal, and anhydrous saccharin sodium is a powder. Under the same conditions, saccharin sodium dihydrate will reduce the contact surface with air, is not easy to lose sodium ions, and delays the shelf life. Therefore, saccharin sodium raw materials generally require two crystal waters, that is, saccharin sodium dihydrate.

[0006] The detection methods of saccharin sodium include spectroscopy, chromatography, and liquid chromatography-tandem mass spectrometry. Among them, high-performance liquid chromatography-mass spectrometry is the most widely used. In particular, the food industry has adopted it as the national standard method for detecting saccharin sodium in food. The existing standard methods only involve the detection method of saccharin sodium in food, without conducting quality evaluation on saccharin sodium raw materials, nor detecting the saccharin sodium content in the varnish during the production process. Although high-performance liquid chromatography can detect the quality of saccharin sodium raw materials and the saccharin sodium content during the production process, its detection cost is high, the detection time is long, the pretreatment is complex, baseline drift and tailing may occur due to insufficient pre-detection equilibration, resulting in inaccurate quantification. Ammonium acetate solution is prone to crystallization, leading to an increase in column pressure of the chromatographic column and even blocking the chromatographic column. Therefore, the chromatographic column needs to be rinsed after each detection, which requires high requirements for inspectors. At the same time, the measured concentration generally needs to be lower than 0.5 mg / mL, and high-concentration saccharin sodium samples cannot be measured.

[0007] Therefore, methods for quality evaluation of saccharin sodium raw materials and detection of saccharin sodium content in the varnish during the production process need to be further studied and developed. Summary of the Invention

[0008] One of the objectives of the present invention is to provide a method for extraction, separation, and detection of saccharin sodium in sweet varnish, which can quickly and accurately determine the content of saccharin sodium in sweet varnish.

[0009] Another objective of the present invention is to provide a method for detecting the quality of saccharin sodium raw materials (i.e., saccharin sodium dihydrate), which can quickly and accurately determine whether the quality of saccharin sodium raw materials is qualified without complex pretreatment.

[0010] To this end, in the first aspect of the present invention, the present invention provides a method for determining the mass fraction of saccharin sodium in sweet varnish, which includes:

[0011] 1) Mix the varnish to be tested with an aqueous sodium chloride solution, shake, and centrifuge to obtain the lower clear liquid. Among them, the mass fraction of sodium chloride in the aqueous sodium chloride solution is 13-17% (such as 13%, 13.5%, 14%, 14.5%, 15%, 15.5%, 16%, 16.5%, or 17%), preferably 15%;

[0012] 2) Take the lower clear liquid and use differential scanning calorimetry to determine the mass fraction of saccharin sodium in the lower clear liquid;

[0013] 3) Determine the mass fraction of saccharin sodium in the varnish to be tested through the following formula,

[0014]

[0015] In the formula:

[0016] χ——the mass fraction of saccharin sodium in the varnish to be tested;

[0017] χ l —— mass fraction of saccharin sodium in the lower-layer clear liquid;

[0018] m2—— mass of the varnish to be measured, g;

[0019] m1—— sampling amount of the lower-layer clear liquid, g.

[0020] In some embodiments, step 2) is carried out through the following steps:

[0021] 2-1) Provide aqueous saccharin sodium solutions with different mass fractions;

[0022] 2-2) Use differential scanning calorimetry to measure the DSC curves of the aqueous saccharin sodium solutions with different mass fractions, and obtain the peak areas of the saccharin sodium melting peaks of each solution;

[0023] 2-3) Take the saccharin sodium mass fraction as the abscissa and the peak area of the saccharin sodium melting peak as the ordinate to establish a saccharin sodium mass fraction - saccharin sodium melting peak area standard curve;

[0024] 2-4) Take the lower-layer clear liquid, use differential scanning calorimetry to measure the DSC curve of the lower-layer clear liquid, and obtain the peak area of the saccharin sodium melting peak of the lower-layer clear liquid;

[0025] 2-5) Substitute the peak area of the saccharin sodium melting peak of the lower-layer clear liquid into the saccharin sodium mass fraction - saccharin sodium melting peak area standard curve to obtain the mass fraction of saccharin sodium in the lower-layer clear liquid.

[0026] In some embodiments, the peak temperature of the saccharin sodium melting peak is 356.21 - 372.89 °C (such as 356.21 °C, 356.5 °C, 257 °C, 357.5 °C, 358 °C, 358.5 °C, 359 °C, 359.5 °C, 360 °C, 360.78 °C, 360.97 °C, 361.76 °C, 361.77 °C, 362.00 °C, 362.17 °C, 362.21 °C, 362.22 °C, 362.43 °C, 362.58 °C, 362.71 °C, 362.86 °C, 363.16 °C, 363.45 °C, 363.77 °C, 364.43 °C, 364.99 °C, 365.38 °C, 365.49 °C, 365.63 °C, 366.02 °C, 367.10 °C, 367.82 °C, 368.25 °C, 369.29 °C, 370.67 °C, 371 °C, 371.5 °C, 372 °C or 372.89 °C).

[0027] In some embodiments, the mass fraction of the sodium saccharin aqueous solution is 0 - 0.4% (such as 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35% or 0.4%).

[0028] In some embodiments, in the differential scanning calorimetry, the starting temperature is 90 °C and the ending temperature is 400 °C.

[0029] In some embodiments, in the differential scanning calorimetry, the heating rate is 15 °C / min.

[0030] In some embodiments, in the differential scanning calorimetry, the differential scanning calorimetry is carried out under a nitrogen atmosphere.

[0031] In some embodiments, in the differential scanning calorimetry, the flow rate of the nitrogen is 40 - 60 mL / min, such as 40 mL / min, 45 mL / min, 50 mL / min, 55 mL / min or 60 mL / min, specifically 50 mL / min.

[0032] In some embodiments, the ratio of the mass of the varnish to be measured to the mass of the sodium chloride aqueous solution is (5 - 10):1, for example 5:1, 5.5:1, 6:1, 6.5:1, 7:1, 7.5:1, 8:1, 8.5:1, 9:1, 9.5:1 or 10:1, preferably 8:1.

[0033] In some embodiments, the mass of the varnish to be measured is 5 - 10 g, such as 5 g, 5.5 g, 6 g, 6.5 g, 7 g, 7.5 g, 8 g, 8.5 g, 9 g, 9.5 g or 10 g, preferably 8 g.

[0034] In some embodiments, the rotation speed of the centrifugation is 4000 - 6000 rpm, such as 4000 rpm, 4500 rpm, 5000 rpm, 5500 rpm or 6000 rpm, preferably 5000 rpm.

[0035] In some embodiments, the time of the centrifugation is 5 - 30 min, such as 5 min, 10 min, 15 min, 20 min, 25 min or 30 min, preferably 15 min.

[0036] In some embodiments, step 1) is carried out at room temperature.

[0037] In some embodiments, the sampling amount of the lower clear liquid is 10 - 15 mg, such as 10 mg, 11 mg, 12 mg, 13 mg, 14 mg or 15 mg.

[0038] In a second aspect of the present invention, the present invention provides a method for detecting the quality of a saccharin sodium dihydrate sample, which comprises:

[0039] 1) Taking a saccharin sodium dihydrate sample to be tested, and determining the DSC curve of the saccharin sodium dihydrate sample to be tested through two heating-cooling procedures by differential scanning calorimetry; wherein, in the first heating-cooling, the starting temperature of the heating procedure is T1, the ending temperature is T2, the starting temperature of the cooling procedure is T2, and the ending temperature is T1; in the second heating-cooling, the starting temperature of the heating procedure is T1, the ending temperature is T2, the starting temperature of the cooling procedure is T2, and the ending temperature is T1;

[0040] 2) If the DSC curve of the saccharin sodium dihydrate sample to be tested simultaneously meets the following three conditions a)-c), the sample to be tested is determined to be qualified; if the DSC curve of the sample to be tested does not simultaneously meet the following three conditions a)-c), the sample to be tested is determined to be unqualified;

[0041] a) In the DSC curve of the heating procedure of the first heating-cooling, the number of peaks is 4;

[0042] b) In the DSC curves of the heating procedures of the first heating-cooling and the second heating-cooling, a saccharin sodium melting peak appears, and in the DSC curve of the heating procedure of the first heating-cooling, the peak temperature of the melting peak is 356.21-372.89 °C (for example, 356.21 °C, 356.5 °C, 257 °C, 357.5 °C, 358 °C, 358.5 °C, 359 °C, 359.5 °C, 360 °C, 360.78 °C, 360.97 °C, 361.76 °C, 361.77 °C, 362.00 °C, 362.17 °C, 362.21 °C, 362.22 °C, 362.43 °C, 362.58 °C, 362.71 °C, 362.86 °C, 363.16 °C, 363.45 °C, 363.77 °C, 364.43 °C, 364.99 °C, 365.38 °C, 365.49 °C, 365.63 °C, 366.02 °C, 367.10 °C, 367.82 °C, 368.25 °C, 369.29 °C, 370.67 °C, 371 °C, 371.5 °C, 372 °C or 372.89 °C);

[0043] c) In the DSC curves of the cooling procedures of the first heating-cooling and the second heating-cooling, a saccharin sodium crystallization peak appears.

[0044] In some embodiments, T1 is 40 °C and T2 is 400 °C.

[0045] In some embodiments, in the heating procedures of the first heating-cooling and the second heating-cooling, the heating rate is 15 °C / min.

[0046] In some embodiments, in the cooling procedures of the first heating-cooling and the second heating-cooling, the cooling rate is 15 °C / min.

[0047] In some embodiments, the differential scanning calorimetry is carried out under a nitrogen atmosphere.

[0048] In some embodiments, the flow rate of the nitrogen is 40 - 60 mL / min, such as 40 mL / min, 45 mL / min, 50 mL / min, 55 mL / min or 60 mL / min, specifically 50 mL / min.

[0049] In some embodiments, the weight of the saccharin sodium dihydrate sample to be measured is 5 - 14 mg (such as 5 mg, 5.5 mg, 5.8 mg, 6 mg, 6.5 mg, 7 mg, 7.5 mg, 7.9 mg, 8 mg, 8.5 mg, 9 mg, 9.5 mg, 9.7 mg, 10 mg, 10.5 mg, 11 mg, 11.5 mg, 12 mg, 12.2 mg, 12.5 mg, 13 mg, 13.5 mg or 14 mg), preferably 8 - 12 mg, such as 9.7 mg or 10 mg.

[0050] In some embodiments, in step 2), condition a) is that in the DSC curve of the heating procedure of the first heating-cooling, the number of peaks is 4, and the peak temperature of the first peak is 66 - 69 °C (such as 66 °C, 66.07 °C, 66.5 °C, 66.76 °C, 66.92 °C, 67 °C, 67.10 °C, 67.39 °C, 67.5 °C, 68 °C, 68.37 °C, 68.5 °C or 69 °C), the peak temperature of the second peak is 110 - 113 °C (such as 110 °C, 110.5 °C, 110.74 °C, 111 °C, 111.5 °C, 111.94 °C, 112 °C, 112.19 °C, 112.5 °C, 112.54 °C, 112.81 °C, 112.91 °C or 113 °C), and the peak temperature of the third peak is 134 - 137 °C (134 °C, 134.5 °C, 134.82 °C, 135 °C, 135.5 °C, 135.73 °C, 135.83 °C, 135.87 °C, 136 °C, 136.04 °C, 136.09 °C, 136.5 °C or 137 °C).

[0051] In some embodiments, in step 2), condition b) is that in the DSC curves of the heating programs for the first heating-cooling and the second heating-cooling, a saccharin sodium melting peak appears in both; and in the DSC curve of the heating program for the first heating-cooling, the fourth peak is a melting peak, and the peak temperature of the melting peak is 356.21 to 372.89 °C (such as 356.21 °C, 356.5 °C, 257 °C, 357.5 °C, 358 °C, 358.5 °C, 359 °C, 359.5 °C, 360 °C, 360.78 °C, 360.97 °C, 361.76 °C, 361.77 °C, 362.00 °C, 362.17 °C, 362.21 °C, 362.22 °C, 362.43 °C, 362.58 °C, 362.71 °C, 362.86 °C, 363.16 °C, 363.45 °C, 363.77 °C, 364.43 °C, 364.99 °C, 365.38 °C, 365.49 °C, 365.63 °C, 366.02 °C, 367.10 °C, 367.82 °C, 368.25 °C, 369.29 °C, 370.67 °C, 371 °C, 371.5 °C, 372 °C or 372.89 °C); in the DSC curve of the heating program for the second heating-cooling, the number of peaks is 1, the peak is a melting peak, and the peak temperature of the melting peak is 356.21 to 372.89 °C (such as 356.21 °C, 356.5 °C, 257 °C, 357.5 °C, 358 °C, 358.5 °C, 359 °C, 359.5 °C, 360 °C, 360.78 °C, 360.97 °C, 361.76 °C, 361.77 °C, 362.00 °C, 362.17 °C, 362.21 °C, 362.22 °C, 362.43 °C, 362.58 °C, 362.71 °C, 362.86 °C, 363.16 °C, 363.45 °C, 363.77 °C, 364.43 °C, 364.99 °C, 365.38 °C, 365.49 °C, 365.63 °C, 366.02 °C, 367.10 °C, 367.82 °C, 368.25 °C, 369.29 °C, 370.67 °C, 371 °C, 371.5 °C, 372 °C or 372.89 °C), preferably 360 - 362 °C.

[0054] In some embodiments, in step 2), condition c) is that in the DSC curves of the cooling procedures of the first heating-cooling and the second heating-cooling, saccharin sodium crystallization peaks appear; and in the DSC curve of the cooling procedure of the first heating-cooling, the number of peaks is 1, the peak is a crystallization peak, and the peak temperature of the crystallization peak is 296 - 304 °C (296 °C, 296.5 °C, 297 °C, 297.5 °C, 298 °C, 298.5 °C, 299 °C, 299.5 °C, 299.90 °C, 300 °C, 300.5 °C, 300.84 °C, 301 °C, 301.5 °C, 301.69 °C, 302 °C, 302.05 °C, 302.47 °C, 302.5 °C, 303 °C, 303.18 °C, 303.5 °C or 304 °C), preferably 299 - 304 °C; in the DSC curve of the cooling procedure of the second heating-cooling, the number of peaks is 1, the peak is a crystallization peak, and the peak temperature of the crystallization peak is 296 - 304 °C (296 °C, 296.02 °C, 296.30 °C, 296.5 °C, 297 °C, 297.33 °C, 297.5 °C, 297.96 °C, 298 °C, 298.5 °C, 299 °C, 299.36 °C, 299.5 °C, 299.90 °C, 300 °C, 300.5 °C, 300.79 °C, 300.84 °C, 301 °C, 301.5 °C, 301.69 °C, 302 °C, 302.05 °C, 302.47 °C, 302.5 °C, 303 °C, 303.18 °C, 303.5 °C or 304 °C), preferably 296 - 301 °C.

[0055] In the present invention, when determining that the saccharin sodium dihydrate sample is qualified by the method of detecting the mass of the saccharin sodium dihydrate sample, the purity of the sample detected by high performance liquid chromatography is not less than 90%. Among them, those skilled in the art can conventionally know the detection method of high performance liquid chromatography. An exemplary detection method of high performance liquid chromatography is as follows.

[0056] High performance liquid chromatography method: The sample is extracted with water, separated by high performance liquid chromatography, qualitatively analyzed according to the peak retention time, and quantitatively analyzed according to the peak area.

[0057] Sample pretreatment: Weigh 0.1 g of the sample, place it in a 50 ml stoppered conical flask, add 20 ml of distilled water, shake well on a shaker to obtain a primary sample solution. Then take 0.1 ml of the primary sample solution, place it in a 50 ml stoppered conical flask, add 20 ml of distilled water, shake well on a shaker to obtain a secondary sample solution.

[0058] Chromatographic column: C18 column, 250 mm × 4.6 mm, 5 μm; Mobile phase: methanol + ammonium acetate solution (5% + 95%); Flow rate: 1 ml·min -1 ; Column temperature: 35 °C; Detection wavelength: 230 nm; Injection volume: 10 μl.

[0059] The content of saccharin sodium in the sample is calculated according to the following formula:

[0060]

[0061] In the formula:

[0062] χ—the content of the component to be measured in the sample, unit: g / kg;

[0063] c—the concentration of the analyte in the sample solution obtained from the standard curve, unit: mg / ml;

[0064] V—the volume of sample constant volume, unit: ml;

[0065] m—the mass of the sample, unit: g.

[0066] In the present invention, room temperature refers to 15-25 °C, such as 25 °C.

[0067] Beneficial effects

[0068] 1. The present invention provides a method for detecting the quality of saccharin sodium raw material (i.e., saccharin sodium dihydrate). This method does not require complex pretreatment, and judges whether the quality of the test sample is qualified by the number of characteristic peaks and the range of melting peak 1 (356.21, 372.89). The result of this method is consistent with that of high performance liquid chromatography test, and can quickly and accurately judge the quality of saccharin sodium raw material.

[0069] 2. The present invention provides a method for extraction, separation and detection of saccharin sodium in sweet varnish. This method can quickly and accurately determine the content of saccharin sodium in sweet varnish, and has excellent repeatability, stability and accuracy. Description of the drawings

[0070] Figure 1 Shows DSC curves at different heating rates;

[0071] Figure 2 Shows DSC curves of different sample weights;

[0072] Figure 3 Shows the DSC curve of saccharin sodium dihydrate standard;

[0073] Figure 4 Shows the normal distribution diagram of melting peak 1;

[0074] Figure 5 Shows the DSC curves of saccharin sodium test samples 1-9;

[0075] Figure 6 Shows the DSC curve of sweet varnish;

[0076] Figure 7The DSC curve of the supernatant after adding 15% sodium chloride aqueous solution is shown;

[0077] Figure 8 The line graph of the saccharin sodium content extracted with different concentrations of sodium chloride aqueous solution is shown;

[0078] Figure 9 The DSC curves of saccharin sodium aqueous solutions with different mass fractions are shown;

[0079] Figure 10 The standard curve of saccharin sodium is shown. Detailed implementation manners

[0080] The implementation scheme of the present invention will be described in detail below in conjunction with the drawings and embodiments. However, those skilled in the art will understand that the following drawings and embodiments are only used to illustrate the present invention, rather than limiting the scope of the present invention. According to the following detailed description of the drawings and preferred implementation schemes, various objects and advantageous aspects of the present invention will become apparent to those skilled in the art.

[0081] Example 1: Method for detecting the quality of saccharin sodium dihydrate sample by differential scanning calorimeter

[0082] 1. Program setting and determination of sample weight

[0083] 1.1 Determination of starting and ending temperatures

[0084] The melting point of saccharin sodium with two crystal waters in the CAS database is 228 °C, and the melting point of saccharin sodium without crystal water > 300 °C. As mentioned above, the purpose of this application is to detect saccharin sodium with two crystal waters. The endothermic peak of water is around 100 °C. As the temperature rises, it is expected to lose two crystal waters, and the final melting peak presented is expected to be the melting peak of saccharin sodium without crystal water. Therefore, the starting temperature is initially set to 40 °C and the ending temperature is set to 400 °C.

[0085] Further, taking the sample of saccharin sodium dihydrate with a purity greater than 90% in our company as an example to determine the heating and cooling rates and sample weight.

[0086] 1.2 Determination of heating and cooling rates

[0087] Weigh about 10 mg of the sample and place it in a 40 μl standard aluminum crucible, then pierce holes and seal it. The starting and ending points are set to 40 °C and 400 °C respectively, and the heating rates are set to 5 °C / min, 10 °C / min, 15 °C / min, 20 °C / min, 30 °C / min in sequence, and observe the heating curve. As Figure 1As shown, the heating rate has an impact on the peak value of the melting peak. The highest value is 372.12 °C at 20 °C / min, and the lowest value is 361.58 °C at 30 °C / min; it also has a certain impact on the melting peak area. The highest value is -73.87 J·g at 5 °C / min -1 , and the lowest value is -113.63 J·g at 15 °C / min -1 ; it also has an impact on the plateau near 100 - 125 °C and the absorption peak near 140 °C. To ensure the comparability of measurement data, the heating rate should be kept consistent. To better present the endothermic peak, exothermic peak, and plateau of the DSC curve, the heating rate is set to be consistent. The response values of saccharin sodium are the highest at heating and cooling rates of 30 °C / min, 15 °C / min, and 10 °C / min. However, at 30 °C / min, the peak shape of saccharin sodium is poor, and samples are prone to overflow during rapid heating, resulting in inaccurate quantification. Therefore, to balance measurement efficiency and accuracy, the heating and cooling rate is selected as 15 °C / min.

[0088] 1.3 Determination of sample weight

[0089] Weigh 5.8 mg, 7.9 mg, 9.7 mg, 12.2 mg, and 14.7 mg of the sample and place them in a 40 μl standard aluminum crucible. Punch holes and seal the sample for preparation. The heating rate is 15 °C / min, and observe the heating curve. As Figure 2 shown, it can be seen that the sample weight has little impact on the peak value of the melting peak. The melting peak is almost near 362 °C. However, when the sample weight reaches 14.7 mg, the melting peak splits into two small peaks; it also has little impact on the melting peak area, basically -112 J·g -1 ; it has a slight impact on the plateau near 100 - 125 °C, and the plateau of 9.7 mg is slightly longer. To better present the plateau of the DSC curve, the sample weight is set at about 9.7 mg.

[0090] 1.4 Sample detection method

[0091] Sample pretreatment: Weigh about 10 mg of saccharin sodium dihydrate sample, place it in a 40 μl standard aluminum crucible, punch holes and seal the sample for preparation.

[0092] Program settings: Conduct under a nitrogen atmosphere with a flow rate of 50 ml / min, with two heating and cooling cycles ①②. Specifically:

[0093] Heating ① program segment: Heat from 40 °C to 400 °C at a rate of 15 °C / min;

[0094] Cooling ① program segment: Cool from 400 °C to 40 °C at a rate of 15 °C / min;

[0095] Heating ② program segment: Heat from 40 °C to 400 °C at a rate of 15 °C / min;

[0096] Cooling ② program segment: Cool from 400 °C to 40 °C at a rate of 15 °C / min.

[0097] Determination of standard samples

[0098] Measure the standard sample of saccharin sodium dihydrate, and the specific results are as Figure 3 shown.

[0099] Figure 3 Among them, heating ①: The standard sample of saccharin sodium dihydrate has 4 characteristic peaks, and their temperatures are respectively located at 67.39 °C, 112.91 °C, 136.04 °C, and 362.00 °C, among which 362.00 °C is the melting peak; cooling ①: The crystallization peak peak appears at 303.18 °C. Heating ②: The first three peaks before 200 °C disappear, the curve is flat, and the peak temperature of the melting peak is 361.45 °C; cooling ②: The crystallization peak peak is 297.33 °C. Comparing heating and cooling ② with heating and cooling ①, the first three peaks before 200 °C disappear, and the temperatures of the melting peak and the crystallization peak are not much different, indicating that the standard sample of saccharin sodium dihydrate is stable during the two heating and cooling processes. Conduct multiple repeated tests on the standard sample, and the test results are shown in Table 1. The highest relative standard deviation is 1.27%, indicating that the repeatability of the method is good.

[0100] Table 1: DSC data of saccharin sodium dihydrate standard sample

[0101]

[0102]

[0103] 3 Quality determination method of saccharin sodium dihydrate

[0104] The purity is calculated according to the following formula from the data of high performance liquid chromatography:

[0105]

[0106] Judge that the high performance liquid purity is not less than 90% as qualified. Select 22 saccharin sodium dihydrate samples with a purity of not less than 90% for DSC testing, monitor the value of melting peak 1, and conduct statistical analysis on the measured results. The results are shown in Table 2, Table 3 and Figure 4 .

[0107] Table 2: DSC data of samples with a purity of not less than 90%

[0108] Sample Melting peak 1 Sample Melting peak 1 P1 362.86 P12 362.22 P2 363.77 P13 367.82 P3 364.99 P14 370.67 P4 363.16 P15 363.45 P5 365.38 P16 361.77 P6 368.25 P17 364.43 P7 367.10 P18 366.02 P8 369.29 P19 362.58 P9 365.49 P20 361.77 P10 365.63 P21 360.97 P11 361.77 P22 360.78

[0109] Table 3: Statistical analysis results of melting peak 1

[0110]

[0111] The p-value of melting peak 1 = 0.44693 > 0.05. At the 0.05 level, the data significantly comes from a normal distribution population. Thus, the confidence interval of the sample can be obtained according to the confidence level. When the confidence level is 99.73%, the confidence interval is (μ - 3σ, μ + 3σ), where μ is the average value of melting peak 1 of 22 samples, and σ is the standard deviation. At this time, the range of melting peak 1 is (356.21, 372.89). Under the same conditions, the same stable sample is measured 5 times in a short time, and its relative standard deviation is 0.10%, which is far less than 5%. It can be considered that it has good repeatability. Therefore, the range of melting peak 1 obtained by the above statistical analysis is used as the basis for judging qualification.

[0112] Thus, a quality evaluation method is obtained: satisfying the 4 characteristic peaks of the standard product of saccharin sodium dihydrate during heating ①, with melting peaks and crystallization peaks appearing during the heating and cooling process, and the peak temperature range of melting peak 1 being (356.21, 372.89), it can be considered that the quality of saccharin sodium dihydrate is qualified.

[0113] 4 Determination and verification of saccharin sodium dihydrate raw materials

[0114] Randomly select 9 kinds of saccharin sodium dihydrate on the market as test samples 1 - 9, and conduct DSC tests according to the above program settings. As shown in Table 4 and Figure 5 shown, test sample 2 has no melting peak and crystallization peak; test sample 5 has one more peak during heating ①, and has no melting peak 2 and crystallization peak; test sample 7 has no characteristic peak 2, which indicates that the quality of test samples 2, 5, and 7 is unqualified.

[0115] Use a high-performance liquid chromatograph to verify the tests of test samples 1 - 9. As shown in Table 4, the purity of test sample 2 is 0, the purity of test sample 5 is 54.31%, and the purity of test sample 7 is 66.24%, all of which are unqualified, which is consistent with the DSC test determination results.

[0116] Table 4: DSC data of test samples 1 - 9

[0117]

[0118]

[0119] Example 2: Method for detecting the content of saccharin sodium in sweet varnish by differential scanning calorimeter

[0120] 1. Extraction of saccharin sodium in sweet varnish

[0121] Directly suck 10 mg - 15 mg of sweet varnish and place it in an aluminum crucible (when sucking 20 mg, during the heating process, the liquid in the aluminum crucible boils to the puncture hole, and the sample cell is contaminated; when sucking less than 10 mg, the liquid volatilizes, the content of saccharin sodium is small, and the peak value cannot be significantly shown). Puncture and seal the sample, heat from 40 °C to 400 °C at 15 °C / min, and observe the change of the DSC curve. As Figure 6 shown, an endothermic peak appears at about 87 °C, where ethyl acetate vaporizes, and an exothermic peak appears at about 209 °C, where the varnish decomposes exothermically. No melting peak of saccharin sodium is detected at 300 °C - 400 °C because the content of saccharin sodium in the varnish is small and the DSC endothermic peak is not obvious. Therefore, in order to detect the melting peak of saccharin sodium in the sweet varnish, saccharin sodium should be transferred out of the varnish to increase the concentration of saccharin sodium.

[0122] During the production process, ethyl acetate is added to adjust the viscosity of the sweet varnish. Since saccharin sodium has a high solubility in water, is slightly soluble in varnish and slightly soluble in ethyl acetate, and the density order is: water > varnish > ethyl acetate, and the solubility of varnish in ethyl acetate is greater than that in water. Therefore, the designed scheme is: add water in equal proportion to transfer saccharin sodium from the varnish to water. After centrifugation, obvious stratification is observed. The lower layer is the water layer (containing a small amount of varnish), and the upper layer is the ethyl acetate and varnish layer. The specific designed method is as follows:

[0123] Weigh 8 g of the production varnish at room temperature, add 1 g of saturated sodium chloride aqueous solution, 15% sodium chloride aqueous solution, and water respectively, vortex and shake for 1 min and then centrifuge. Absorb the supernatant into an aluminum cup, dry it at 80 °C to remove ethyl acetate, and measure the content of varnish. As can be seen from Table 5, the content of varnish in the supernatant added with saturated sodium chloride aqueous solution is the largest, and the content of varnish in the supernatant added with water is the smallest, which proves that the solubility of varnish in ethyl acetate can be increased by adding sodium chloride, and then the content of saccharin sodium in the water layer can be increased. At the same time, use a syringe needle to absorb the lower supernatant for DSC testing. By establishing a standard curve of saccharin sodium, calculate the content of saccharin sodium in the lower supernatant, and convert it into the content of saccharin sodium in the production varnish through the following formula:

[0124]

[0125] In the formula:

[0126] χ——The content of saccharin sodium in the sample;

[0127] χ l ——The content of saccharin sodium in the water layer;

[0128] m2——The mass of the sample, g;

[0129] m1——The mass of water, g.

[0130] Figure 7The DSC curve of the supernatant liquid after adding 15% sodium chloride aqueous solution. The endothermic peak at about 125°C is the vaporization of water, and the peak at about 350°C is the melting peak of saccharin sodium. It can be seen from the figure that the presence of sodium chloride does not interfere with the melting peak of saccharin sodium, which may be because the melting point of sodium chloride is 801°C. As shown in Table 6, surprisingly, it is found that the saccharin sodium content measured after adding saturated sodium chloride aqueous solution is the least, which is 0.511%, showing a large deviation from the 0.799% measured by liquid phase; the saccharin sodium content directly extracted with water is 0.699%, also showing a certain gap from the liquid phase measurement result; while when adding 15% sodium chloride aqueous solution, the measured saccharin sodium content of 0.794% is the closest to the saccharin sodium content of 0.799% measured by liquid phase. This indicates that adding 15% sodium chloride aqueous solution can completely extract and separate saccharin sodium from the sweet varnish, and the extraction and separation effect of the sweet varnish is relatively ideal.

[0131] Table 5: Varnish content in the supernatant liquid before and after drying

[0132]

[0133] Table 6: Saccharin sodium content in the supernatant liquid

[0134]

[0135]

[0136] To further verify and determine the optimal concentration of sodium chloride in the sodium chloride aqueous solution, at room temperature, sodium chloride aqueous solutions with sodium chloride mass fractions of 5%, 10%, 15%, 20%, and 25% were prepared. Weigh 8 g of the same sweet varnish, add 1 g of the above five concentrations of sodium chloride aqueous solution respectively, oscillate with a vortex oscillator for about 1 min, centrifuge at 5000 rpm for 15 min with a centrifuge, take 10 - 15 mg of the supernatant liquid and place it in a 40 μl aluminum crucible, make samples by punching holes and sealing, and conduct DSC tests. The results are shown in Table 7 and Figure 8 . The inventor found that adding a certain concentration of sodium chloride aqueous solution helps to extract saccharin sodium from the varnish. When the sodium chloride concentration reaches 15%, the saccharin sodium content reaches the maximum value, but when the concentration exceeds 15%, the saccharin sodium content drops rapidly. Therefore, the experimental results further prove that to ensure that saccharin sodium is extracted as much as possible, the mass fraction of sodium chloride in the used sodium chloride aqueous solution should be 15%.

[0137] Table 7: Saccharin sodium content extracted by sodium chloride solutions with different concentrations

[0138]

[0139] 2. Establishment of the saccharin sodium standard curve

[0140] The water solubility of sodium saccharin is approximately 100 g / 100 mL. Therefore, sodium saccharin aqueous solutions with mass fractions of 0.05, 0.1, 0.2, 0.3, and 0.4 were prepared, vortexed on a vortex oscillator, and the solution was aspirated with a syringe needle and placed in a 40 μL aluminum crucible, covering the entire bottom of the crucible. The solution was approximately 15 mg, and holes were pricked and sealed for sample preparation. Water will gradually evaporate at around 100 °C. To ensure slow evaporation of the solution in the crucible, the initial temperature was set to 90 °C, and it was heated to 400 °C at a rate of 15 °C / min in a nitrogen environment. The DSC curve of the sample was measured to observe the melting peaks of sodium saccharin with different mass fractions.

[0141] As Figure 9 shown, a positive peak area indicates exothermic, and a negative peak area indicates endothermic. The melting peak of sodium saccharin is an endothermic peak. Only focus on the numerical value and ignore the positive and negative signs. When the mass fraction of sodium saccharin is large, the peak area of the melting peak will increase proportionally. Using the mass fraction of sodium saccharin as the abscissa and the peak area of the melting peak (only taking the numerical value) as the ordinate, a standard curve of sodium saccharin was made. As Figure 10 shown, when the mass fraction is in the range of 0 - 0.4%, the peak area of the melting peak has a good linear relationship with the mass fraction, and the linear regression equation is y = 105.3114x + 0.00484 (R 2 = 0.99998).

[0142] 3. Sample pretreatment method

[0143] At room temperature, 8 g of varnish in production was weighed, 1 g of 15% sodium chloride aqueous solution was added, vortexed, and then centrifuged at 5000 rpm for 15 min in a centrifuge. 10 - 15 mg of the supernatant liquid was aspirated and placed in an aluminum crucible, and holes were pricked and sealed for storage.

[0144] 4. DSC program settings

[0145] Under a nitrogen atmosphere with a flow rate of 50 ml / min, it was heated from 90 °C to 400 °C at a rate of 15 °C / min.

[0146] 5. Calculation of the sodium saccharin content (i.e., mass fraction) in the varnish sample

[0147]

[0148] In the formula:

[0149] χ —— Sodium saccharin content in the varnish sample;

[0150] χ l —— Sodium saccharin content in the supernatant liquid;

[0151] m2 —— Mass of the varnish sample, g;

[0152] m1 —— Mass of the aspirated supernatant liquid, g.

[0153] It should be understood that the inventions described herein are not limited to specific methodologies, experimental protocols or reagents, as these can vary. The discussions and examples provided herein are only presented to describe specific embodiments and are not intended to limit the scope of the invention, which is only limited by the claims.

Claims

1. A method for determining the mass fraction of saccharin sodium in a sweet varnish, comprising: 1) Mix the varnish to be tested with an aqueous sodium chloride solution, shake it, and centrifuge it to obtain the lower clear liquid. Among them, the mass fraction of sodium chloride in the aqueous sodium chloride solution is 13-17%, preferably 15%. 2) Take the lower clear liquid and determine the mass fraction of saccharin sodium in the lower clear liquid by differential scanning calorimetry. 3) Determine the mass fraction of saccharin sodium in the varnish to be tested through the following formula In the formula: χ——The mass fraction of saccharin sodium in the varnish to be tested; χ l —— mass fraction of saccharin sodium in the lower supernatant; m2——The mass of the varnish to be tested, g; m1——The sampling amount of the lower clear liquid, g.

2. The method of claim 1, wherein, Step 2) is carried out through the following steps: 2-1) Provide aqueous saccharin sodium solutions with different mass fractions; 2-2) Use differential scanning calorimetry to measure the DSC curves of the aqueous saccharin sodium solutions with different mass fractions, and obtain the peak areas of the saccharin sodium melting peaks of each solution; 2-3) Establish a standard curve of saccharin sodium mass fraction - saccharin sodium melting peak area with the saccharin sodium mass fraction as the abscissa and the saccharin sodium melting peak area as the ordinate; 2-4) Take the lower clear liquid and use the differential scanning calorimetry to measure the DSC curve of the lower clear liquid to obtain the peak area of the saccharin sodium melting peak of the lower clear liquid; 2-5) Substitute the peak area of the saccharin sodium melting peak of the lower clear liquid into the standard curve of saccharin sodium mass fraction - saccharin sodium melting peak area to obtain the mass fraction of saccharin sodium in the lower clear liquid.

3. The method of claim 2, wherein, Step 2) further has one or more of the following technical features selected from (i)-(ii): (i) The peak temperature of the saccharin sodium melting peak is 356.21-372.89°C; (ii) The mass fraction of the aqueous saccharin sodium solution is 0-0.4%.

4. The method of any one of claims 1 - 3, wherein, The differential scanning calorimetry further has one or more of the following technical features selected from (i)-(iii): ( i) The starting temperature is 90°C and the ending temperature is 400°C; (ii) The heating rate is 15°C / min; (iii) The differential scanning calorimetry is carried out under a nitrogen atmosphere Preferably, the flow rate of the nitrogen is 40-60 mL / min, such as 50 mL / min.

5. The method of any one of claims 1 - 4, wherein, The method for determining the mass fraction of saccharin sodium in the sweet varnish further has one or more of the following technical features selected from (i)-(vi): (i) The ratio of the mass of the varnish to be tested to the mass of the aqueous sodium chloride solution is (5-10):1, preferably 8:1; (ii) The mass of the varnish to be tested is 5-10 g, preferably 8 g; (iii) The rotation speed of the centrifugation is 4000-6000 rpm, preferably 5000 rpm; (iv) The centrifugation time is 5-30 min, preferably 15 min; (v) Step 1) is carried out at room temperature; (vi) The sampling amount of the lower clear liquid is 10-15 mg.

6. A method for detecting the quality of a saccharin sodium dihydrate sample, comprising: 1) Take the saccharin sodium dihydrate sample to be tested and use differential scanning calorimetry to measure the DSC curve of the saccharin sodium dihydrate sample to be tested through two heating-cooling procedures; wherein, in the first heating-cooling, the starting temperature of the heating procedure is T1, the ending temperature is T2, the starting temperature of the cooling procedure is T2, and the ending temperature is T1; in the second heating-cooling, the starting temperature of the heating procedure is T1, the ending temperature is T2, the starting temperature of the cooling procedure is T2, and the ending temperature is T1; 2) If the DSC curve of the saccharin sodium dihydrate sample to be tested simultaneously meets the following three conditions a)-c), the sample to be tested is determined to be qualified; if the DSC curve of the sample to be tested does not simultaneously meet the following three conditions a)-c), the sample to be tested is determined to be unqualified; a) In the DSC curve of the heating procedure of the first heating-cooling, the number of peaks is 4; b) In the DSC curves of the heating procedures of the first heating-cooling and the second heating-cooling, a saccharin sodium melting peak appears, and in the DSC curve of the heating procedure of the first heating-cooling, the peak temperature of the melting peak is 356.21 - 372.89 °C; c) In the DSC curves of the cooling procedures of the first heating-cooling and the second heating-cooling, a saccharin sodium crystallization peak appears.

7. The method of claim 6, wherein, The method further has one or more technical features selected from the following (i)-(iii): (i) T1 is 40 °C and T2 is 400 °C; (ii) In the heating procedures of the first heating-cooling and the second heating-cooling, the heating rate is 15 °C / min; (iii) In the cooling procedures of the first heating-cooling and the second heating-cooling, the cooling rate is 15 °C / min; (iv) The differential scanning calorimetry is carried out under a nitrogen atmosphere, Preferably, the flow rate of the nitrogen is 40 - 60 mL / min, such as 50 mL / min; (v) The weight of the saccharin sodium dihydrate sample to be tested is 5 - 14 mg, preferably 8 - 12 mg, such as 9.7 mg or 10 mg.

8. The method of any one of claims 6 - 7, wherein, In step 2), condition a) is that in the DSC curve of the heating procedure of the first heating-cooling, the number of peaks is 4, and the peak temperature of the first peak is 66 - 69 °C, the peak temperature of the second peak is 110 - 113 °C, and the peak temperature of the third peak is 134 - 137 °C.

9. The method of any one of claims 6 - 8, wherein, In step 2), condition b) is that in the DSC curves of the heating procedures of the first heating-cooling and the second heating-cooling, a saccharin sodium melting peak appears; and in the DSC curve of the heating procedure of the first heating-cooling, the fourth peak is a melting peak, and the peak temperature of the melting peak is 356.21 - 372.89 °C; in the DSC curve of the heating procedure of the second heating-cooling, the number of peaks is 1, the peak is a melting peak, and the peak temperature of the melting peak is 356.21 - 372.89 °C, preferably 360 - 362 °C.

10. The method of any one of claims 6 - 9, wherein, In step 2), condition c) is that in the DSC curves of the cooling procedures of the first heating-cooling and the second heating-cooling, a saccharin sodium crystallization peak appears; and in the DSC curve of the cooling procedure of the first heating-cooling, the number of peaks is 1, the peak is a crystallization peak, and the peak temperature of the crystallization peak is 296 - 304°C, preferably 299 - 304°C; in the DSC curve of the cooling procedure of the second heating-cooling, the number of peaks is 1, the peak is a crystallization peak, and the peak temperature of the crystallization peak is 296 - 304°C, preferably 296 - 301°C.

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