On July 28 , 2022 , the National Health Commission promulgated a new national food sulfur dioxide standard " GB5009.34-2022 ", which will be implemented on December 30, 2022. Compared with the original GB 5009.34-2016 , the main changes of the new national standard are as follows:
( 1 ) Revised the original titration method to acid-base titration method.
( 2 ) Add spectrophotometry and ion chromatography.
The first method is acid-base titration method. The pretreatment uses nitrogen-filled distillation method. After the sample is acidified, sulfite and other substances are released under heating conditions to release sulfur dioxide, which is absorbed by hydrogen peroxide solution. The sulfur dioxide is oxidized to sulfate ions. Titrate with sodium oxide standard solution and calculate the content of sulfur dioxide according to the consumption.
The second method of spectrophotometry, the sample is soaked in formaldehyde buffer absorption solution or distilled with acid and nitrogen, so that the sulfur dioxide in it is released and absorbed by the formaldehyde solution to generate a stable hydroxymethanesulfonic acid addition compound, which is combined with pararosaniline hydrochloride under acidic conditions. A blue-violet complex was formed, and the concentration of sulfur dioxide was obtained by measuring the absorbance of the complex.
The third method is ion chromatography. The pretreatment is to convert the sulfite series substances in the sample into sulfur dioxide after acid treatment, which is distilled out with water vapor by nitrogen -filling- steam distillation, and absorbed by hydrogen peroxide and oxidized into sulfur dioxide. Sulfate ions were measured using an ion chromatograph. In Annex B of the Standard, requirements are made for a steam distillation unit (Figure 5 ). Compared with the first two methods, the steam distillation device of ion chromatography is more complicated, which poses a challenge to the efficiency of inspection institutions and food enterprises. At the same time, there are problems such as occupying laboratory space, difficult to control the flow of steam and nitrogen, and difficult to ensure the air tightness of the device, which ultimately affects the test results.
In the new standard, glass nitrogen-filled stills are used in the pretreatment process of the first method and the second method.
Comparison of the new and old national standard detection methods for the determination of food sulfur dioxide (the first method) |
| GB5009.34-2016 | GB5009.34-2022 (new national standard) |
| Detection method | titration | The titration method was changed to: acid-base titration, adding the second method of spectrophotometry and the third method of ion chromatography. |
| scope of test | This standard specifies the method for the determination of total sulfur dioxide in foods such as preserved fruit, dried vegetables, rice noodles, vermicelli, granulated sugar, edible fungi and wine. | The first method is the acid-base titration method, which is suitable for the determination of sulfur dioxide in food;
The second method is the spectrophotometric method. The direct extraction method is suitable for the determination of sulfur dioxide in sugar and white sugar products, starch and starch products, raw wet flour products and other samples that have no oil and no color interference in the extract. The nitrogen-filled distillation extraction method is suitable for the determination of sulfur dioxide. Determination of sulfur dioxide in colored samples such as wine and brown sugar;
The third method is ion chromatography, which is suitable for the determination of sulfur dioxide in food. |
| Sample preparation | 5g homogeneous sample (accurate to 0.001g, the sampling amount depends on the content), liquid sample can directly absorb 5.00mL ~ 10.00mL sample; add 250ml of water; add 10ml of hydrochloric acid. | Take a solid or semi-fluid sample of 20 g ~ 100 g (accurate to 0.01 g, the sampling amount depends on the content); take a liquid sample of 20 mL (g) ~ 200 mL (g); add 20-500 ml of water; Add 10 ml of 6 mol/L hydrochloric acid. |
| Whether nitrogen-filled distillation | no | Nitrogen-filled distillation, flow rate: 1.0-2.0L/min |
| Absorbent | 25mL lead acetate absorption solution | 3% hydrogen peroxide solution 50mL (the first method) |
| Distillation method | 200 ml of distillate was collected, distilled for another 1 minute, and the device inserted into the absorption solution was rinsed with a small amount of distilled water. | The solution in the flask was heated to boiling and kept slightly boiling for 1.5h. |
| Titration method | Add 10 mL of hydrochloric acid and 1 mL of starch indicator solution to the removed iodine flask in turn, shake well and titrate with iodine standard solution until the color of the solution turns blue and does not fade within 30s. At the same time do a blank test. | Allow the absorption solution to cool and shake well, add 3 drops of 2.5 mg/mL methyl red ethanol solution indicator to the absorption solution, titrate with sodium hydroxide standard solution (0.01 mol/L) until it becomes yellow and does not fade for 20 seconds, and At the same time, a blank test was carried out. |
| detection limit and quantification limit | When a 5g solid sample was taken, the limit of detection (LOD) of the method was 3.0mg/kg, and the limit of quantification was 10.0mg/kg; when a 10mL liquid sample was taken, the limit of detection (LOD) of the method was 1.5mg/L, The limit of quantification was 5.0 mg/L. | When using 0.01mol/L sodium hydroxide titration solution, when the solid or semi-fluid sample volume is 35g, the detection limit is 1mg/kg, and the quantification limit is 10mg/kg; when the liquid sampling volume is 50mL (g), the detection limit is The output limit was 1 mg/L (mg/kg), and the quantification limit was 6 mg/L (mg/kg). |
| Product recommended model | ST106-1RW (distillation pretreatment), ST106K2 (automatic, can directly output test results.) | All ST109 series (A is a six-digit, fully automatic model, and the test results are directly output; B is a six-digit; C is an eight-digit, cost-effective model; D is a special machine for ion chromatography steam distillation), the whole system comes standard with automatic addition Acid and nitrogen control device (A adopts digital imported nitrogen controller, other models are rotameter). The whole series is compatible with the detection of sulfur dioxide in traditional Chinese medicine and Chinese herbal medicines. |
Jinan Shengtai Electronic Technology Co., Ltd. has developed the country's first intelligent integrated distillation apparatus (also known as: food sulfur dioxide analyzer) for the " GB5009.34-2016" national standard, model: ST106-1RW , with: far-infrared automatic heating + Automatic weighing and metering distillation + built-in compressor cooling water self-circulation system + automatic cleaning and other special functions, deeply loved by domestic food and drug inspection and testing units at all levels, customs, colleges and universities, scientific research institutes and other units.
In this revision of the new national standard, Jinan Shengtai Technology participated in the verification of the new national standard data throughout the process, and developed four new supporting instruments for this new national standard, ST109A/ST109B/ST109C/ST109D. It can be applied to the fully automatic detection of the first method and the second method or the pretreatment of nitrogen-filled distillation; the third method is the steam distillation of the ion chromatography method. The models of these four products are:
| Jinan Shengtai Technology ST109 series intelligent sulfur dioxide analyzer product parameter comparison table |
| model | ST109A | ST109B | ST109C | ST109D |
| According to the standard | GB5009.34-2022 "Determination of sulfur dioxide in food", 2015 edition, 2020 edition of "Chinese Pharmacopoeia" for the determination of sulfur dioxide in traditional Chinese medicines and Chinese medicinal materials; |
| Corresponding standard | GB5009.34-2022 The first method, the second method | GB5009.34-2022 The first method, the second method | GB5009.34-2022 The first method, the second method | The third law of GB5009.34-2022 |
| Product Positioning | High-end, fully automatic | Standard version | Cost-effective | Special machine for steam distillation |
| Number of samples | 6 | 6 | 8 | 6 |
| flask volume | Conventional double mouth 1000ml flask | Double neck 1000ml custom flask | Conventional double mouth 1000ml flask | Conventional double mouth 500ml flask |
| heating method | Far infrared ceramic heating | Far infrared ceramic heating | Far infrared ceramic heating | Built-in steam source steam heating |
| Condenser tube structure | Reflow type, semi-hidden structure | Reflux condenser | Reflow type, semi-hidden structure | serpentine condenser |
| Automatic acid addition | Automatic acid addition | Automatic acid addition | Automatic acid addition | Automatic acid addition |
| Nitrogen control | Imported digital nitrogen flow controller
200-2000ml/min | Rotameter
200-2000ml/min | Rotameter
200-2000ml/min | Rotameter
200-2000ml/min |
| cooling method | External cooling water circulation machine | Built-in compressor self-circulating cooling system | External cooling water circulation machine | External cooling water circulation machine |
| Control method | Desktop PC | LCD touch screen | LCD touch screen | LCD touch screen |
| automatic titration | Automatic titration with high precision syringe pump | none | none | —— |
| Endpoint identification | High-precision visual sensor, completely simulating the human eye, automatically identifying the end point of titration | none | none | none |
| rated power | 3500W | 3600W | 4500W | 3000W |
| Dimensions (mm) | 735×650×670 | 960×575×410 | 940×650×680 | 960×500×730 |
