CN102998389B - Gas chromatography detection method of corrosion removers in food - Google Patents

Abstract

The invention relates to a detection method for gas chromatographic determination of various preservatives in food. The purpose is that the method should have the characteristics of simple operation, resistance to matrix interference, and reliable results, and is suitable for the accurate determination of various preservatives in food. The technical solution is: a gas chromatographic detection method for various preservatives in food, which is carried out according to the following steps: 1), preparing a sample extract: preparing a liquid sample extract; or preparing a solid sample extract; 2), Concentration: Rotate and concentrate the above sample extract to 0.3-0.5mL in a water bath at 40±2°C, blow dry with nitrogen, and dilute to 2.0-5.0mL with acetone, and pass the sample solution through a 0.45μm filter membrane for testing; 3) , On-machine detection: the above-mentioned liquid to be tested is input into a gas chromatograph equipped with a hydrogen flame detector for detection.

Description

A gas chromatography detection method for multiple preservatives in food

technical field

The invention relates to a detection method, in particular to a detection method for gas chromatographic determination of various preservatives in food.

Background technique

Preservative refers to the agent that inhibits the corruption of substances, that is, it has a continuous inhibitory effect on the growth of microorganisms that use spoilage substances as metabolic substrates, and is widely used in food, daily chemical and other fields.

There are many types of preservatives that are allowed to be added internationally, such as about 50 in the United States and 40 in Japan. At present, my country has only approved 32 kinds of food preservatives that are allowed to be used. They have undergone a lot of scientific experiments before being approved for use. They are all low-toxic and safe varieties, mainly including: benzoic acid and its sodium salt, Sorbic acid and its potassium salt, sulfur dioxide, sodium (potassium) metabisulfite, sodium (calcium) propionate, parabens, dehydroacetic acid, etc. Among them, sorbic acid, benzoic acid and their salts are more widely used. In addition, there are some natural biological preservatives such as nisin, natamycin, chitosan, etc. and new preservatives, such as dimethyl fumarate. As long as the food preservatives used by food manufacturers are strictly controlled within the scope specified in the national standard "Hygienic Standards for the Use of Food Additives" (GB2760-2011) in terms of variety, quantity and scope, they should not cause damage to human health. The product is safe to eat. However, what is regrettable and extremely worrying is that many food production enterprises have violations, illegal use, abuse, and overdose due to the limitation of production costs, the influence of low-quality employees, and the lack of awareness of the hazards of preservatives. The use of food preservatives has led to many foods becoming an "integrated hodgepodge" of additives, including preservatives. Excessive intake will have a certain negative impact on health; excessive addition of preservatives will have a significant impact on society and consumers Impact. Therefore, the establishment of a set of fast, accurate, simple and low-cost detection technical standards can be widely used in beverages, pastries, condiments, candied fruit and other foods, which can improve the detection efficiency of preservatives in food and effectively control the detection It is beneficial to the rational use of preservatives in the production process of enterprises and the rapid monitoring of the addition of preservatives by law enforcement agencies in the process of market circulation; it is of great significance in ensuring food safety, and its social benefits are very significant.

Due to the different structural properties of different preservatives, and the complex and diverse sample matrices, the detection methods for different preservatives and different food types in the current standards are also different. At present, there are many kinds of preservative detection standards, the experimental conditions involved are different, and the types of preservatives are relatively single. It is often impossible to quickly detect multiple common preservatives at one time, resulting in longer inspection cycles and lower inspection efficiency. Common methods for detecting preservatives include liquid chromatography, liquid chromatography-mass spectrometry, gas chromatography, and gas chromatography-mass spectrometry. Although liquid chromatography and liquid chromatography-mass spectrometry can simultaneously determine a variety of preservatives, due to the variety of food sample matrices, the matrix impurities will cause interference, easily cause false positive or false negative results, and affect accurate quantification. Gas chromatography-mass spectrometry has high requirements for instruments and is not suitable for popularization.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies in the background technology and provide a detection method that can simultaneously measure multiple common preservatives in food. Accurate determination of drug content.

In order to achieve the above object, the inventor has carried out extensive and in-depth research experiments, and has determined the following technical solutions:

A gas chromatography detection method for multiple preservatives in food is carried out according to the following steps:

1) Prepare the sample extract:

Preparation of liquid sample extract: Weigh 5-10g of liquid sample into a 125mL separatory funnel, add 10mL saturated NaCl aqueous solution and 1.0mL hydrochloric acid solution for acidification and mix well, then add 1.0mL internal standard solution, and then extract with ether Three times, the ether layer was combined, washed with saturated NaCl aqueous solution until neutral, and the ether layer was dehydrated by anhydrous sodium sulfate for later use; or,

Preparation of solid sample extract: Weigh 5-10g of solid sample into a 100mL volumetric flask, add water and soak in a water bath at 80±2°C for 30-60min, take it out and cool to room temperature, add water to make up to 100mL; filter again, and take the filtrate 10.0-25.0mL in a 125mL separatory funnel; add 10mL saturated NaCl aqueous solution and 1.0mL hydrochloric acid solution and mix well, then add 1.0mL internal standard solution, then extract three times with ether, combine the ether layers, wash with saturated NaCl aqueous solution until neutral , the ether layer was dehydrated by anhydrous sodium sulfate for subsequent use;

2) Concentration: Rotate and concentrate the above sample extract to 0.3-0.5mL in a water bath at 40±2°C, blow dry with nitrogen, and dilute to 2.0-5.0mL with acetone, pass the sample solution through a 0.45μm filter membrane to be tested ;

3) On-machine detection: Input the above-mentioned liquid to be tested into a gas chromatograph equipped with a hydrogen flame detector for detection.

The multiple preservatives refer to propionic acid, sorbic acid, benzoic acid, dehydroacetic acid, methyl p-hydroxybenzoate, ethyl p-hydroxybenzoate, propyl p-hydroxybenzoate, isopropyl p-hydroxybenzoate , Butylparaben, Isobutylparaben, Heptylparaben, Dimethylfumarate.

The hydrochloric acid used in the step 1) for acidification refers to a mixed solution prepared by equal volumes of concentrated hydrochloric acid with a concentration of 12moL/L and water.

In the step 1), the internal standard solution is composed of undecanoic acid and acetone, and the content of undecanoic acid is 1-2 mg/mL.

In the step 1), ether was used for extraction three times, and the ethers used in sequence were 50 mL, 30 mL, and 30 mL.

The beneficial effects of the present invention are:

1) The sample is acidified with hydrochloric acid and extracted with ether, which avoids the interference of the sample matrix on the chromatographic peak;

2) Quantitative determination of various preservatives in food by internal standard (undecanoic acid) method can effectively reduce the influence of extraction efficiency on the results during sample preparation;

3) The detection of the standard working solution proves that the detection method established by the present invention has the advantages of one-time detection of many types of preservatives, good linearity of detection results, high detection sensitivity (detection limit is 0.84-5.01mg/kg), anti-specific Good performance (precision 1.9-4.3%, recovery rate 88.9-101.6%), easy operation, resistance to matrix interference, and reliable results are suitable for the accurate determination of various preservatives in food, and provide food quality supervision. With strong technical support.

Description of drawings

Figure 1 is a gas chromatographic schematic diagram of a variety of preservatives mixed standards; 1-12 in the figure refer to: 1-propionic acid, 2-dimethyl fumarate, 3-sorbic acid, 4-dehydroacetic acid, 5-endo Undecanoic acid, 6-benzoic acid, 7-methyl p-hydroxybenzoate, 8-isopropyl p-hydroxybenzoate, 9-ethyl p-hydroxybenzoate, 10-propyl p-hydroxybenzoate, 11- Butylparaben and isobutylparaben, 12-heptylparaben.

Fig. 2 is the gas chromatogram schematic diagram of soy sauce.

Fig. 3 is a schematic diagram of the gas chromatogram of orange juice beverage.

Figure 4 is a schematic diagram of the gas chromatogram of vinegar.

Fig. 5 is a gas chromatogram schematic diagram of egg yolk crisp.

Detailed ways

The idea of the present invention is to weigh a certain amount of liquid sample or solid sample filtrate soaked in a water bath in a container, add hydrochloric acid for acidification, saturated aqueous sodium chloride solution and a fixed amount of internal standard solution, mix well, and extract 3 times with ether , combine the ether layers, wash with saturated sodium chloride aqueous solution to neutrality, discard the water layer, and dehydrate the ether layer for later use; rotary evaporate the above extract to nearly dryness, dry it with nitrogen gas, dilute it with acetone, and pass the sample solution through the membrane After that, it is to be tested; the above-mentioned liquid to be tested is input into a gas chromatograph equipped with a hydrogen flame detector for detection.

1) The first point in the method is to detect multiple preservatives simultaneously (multiple preservatives include propionic acid, sorbic acid, benzoic acid, dehydroacetic acid, methyl p-hydroxybenzoate, ethyl p-hydroxybenzoate, p-hydroxybenzoate propylparaben, isopropylparaben, butylparaben, isobutylparaben, heptylparaben, dimethyl fumarate); covering 12 preservatives at the same time Rapid determination improves the efficiency of detection;

2) The second key point in the method is that the sample is acidified with 1:1 hydrochloric acid and extracted three times with ether, which avoids the interference of the sample matrix on the chromatographic peak;

3) The third point in the method is to use the internal standard (undecanoic acid) method to quantitatively determine various preservatives in food, which can effectively reduce the influence of extraction efficiency on the results during sample preparation.

The relevant details of the present invention are described as follows below:

1 Reagents and materials

Unless otherwise stated, all reagents are of analytical grade, and water is third-grade water specified in GB/T 6682.

1:1 hydrochloric acid solution: prepare by mixing concentrated hydrochloric acid with a concentration of 12moL/L and water in equal volumes;

Ether;

Saturated sodium chloride aqueous solution: add sodium chloride to distilled water, stir to dissolve to saturation;

Anhydrous sodium sulfate;

acetone;

Undecanoic acid: used as an internal standard, weigh 0.1000g, dissolve and dilute with acetone to 100mL, and make it into an internal standard solution for later use. The content of undecanoic acid in the internal standard solution is 1mg/mL;

12 standard preservatives (propionic acid, sorbic acid, benzoic acid, dehydroacetic acid, methyl p-hydroxybenzoate, ethyl p-hydroxybenzoate, propyl p-hydroxybenzoate, isopropyl p-hydroxybenzoate, p-hydroxybenzoate Butylparaben, Isobutylparaben, Heptylparaben, Dimethylfumarate);

Preservative standard stock solution: Weigh 0.2000g of preservative standard, dissolve and dilute to 100mL with acetone, so that the concentration of each preservative is 2mg/mL;

Mixed standard working solution: Pipette 0.1mL, 0.2mL, 0.5mL, 1.0mL, 2.0mL, 5.0mL of preservative standard stock solution into six 5.0mL volumetric flasks, and then transfer undecanoic acid into the volumetric flasks Internal standard solution 1.0mL, dilute to 5.0mL with acetone, prepare a series of mixed standard working solutions, so that the final concentrations of each preservative are 0.04mg/mL, 0.08mg/mL, 0.2mg/mL, 0.4mg/mL, 1.0mg/mL, 2.5mg/mL;

0.45μm filter membrane.

2 Instruments and equipment

Gas chromatograph: equipped with FID detector;

Analytical balance: the sensitivity is 0.0001g and 0.01g;

Water bath;

Rotary evaporator.

3 sample processing

3.1 Liquid samples (such as beverages, soy sauce, etc.)

Weigh 5-10g of the sample (accurate to 0.01g) into a 125mL separatory funnel, add 10mL saturated NaCl aqueous solution and 1mL hydrochloric acid solution and mix well, then add 1mL internal standard solution, and then extract three times with 50mL, 30mL, and 30mL ether respectively, The ether layers were combined, washed with 30mL saturated NaCl aqueous solution until neutral, dehydrated by anhydrous sodium sulfate, concentrated in a water bath at 40±2°C until nearly dry, blown dry with nitrogen, and fixed to 2.0-5.0mL with acetone; the sample solution was passed through 0.45 After the μm filter membrane to be tested.

3.2 Solid samples (such as pastries, candied fruit, etc.)

Weigh 5-10g of the sample (accurate to 0.01g) into a 100mL volumetric flask, add water and soak in a water bath at 80±2°C for 30-60min, take it out and cool it to room temperature, add water to make up to 100mL, filter, and take the filtrate 10.0-25.0mL in 125mL separatory funnel; add 10mL saturated NaCl aqueous solution and 1.0mL hydrochloric acid solution and mix well, then add 1.0mL internal standard solution, then extract three times with 50mL, 30mL, and 30mL diethyl ether, combine the ether layers, and wash with 30mL saturated NaCl aqueous solution until Neutral, dehydrated with anhydrous sodium sulfate, concentrated in a water bath at 40±2°C to near dryness, blown dry with nitrogen, and dilute to 2.0-5.0mL with acetone; the sample solution is tested after passing through a 0.45μm filter membrane.

4 Gas Chromatography Determination

4.1 GC reference conditions

Chromatographic column: HP-innowax, 30m×320μm×0.25μm;

Column temperature: initial temperature 130°C, rise to 170°C at 10°C/min, stay for 3 minutes, then rise to 260°C at 20°C/min, stay for 21.5 minutes;

Injection port temperature: 250°C;

Detector temperature: 260°C;

Carrier gas: high-purity N2, flow rate 0.8mL/min;

Injection volume: 1μL; split ratio: 10:1;

4.2 Drawing of standard curve

Inject the diluted standard working solution according to the concentration from low to high, and plot the peak area-concentration to obtain the standard curve regression equation. The standard spectrum is shown in Figure 1.

5 Linear relationship and detection limit

Take the ratio of the mass concentration of each preservative to the internal standard (undecanoic acid) as the abscissa, and use the corresponding peak area as the ordinate to perform linear regression, and the linear concentration range is 0.04-2.50 mg/mL. According to the signal-to-noise ratio of 3 times, 5.00g of the sample (liquid) was actually weighed, and the final volume was adjusted to 5.0mL. The correlation coefficient ^R2 of the linear regression equation of various preservatives was in the range of 0.99860-0.99980, and the minimum detection limit was 0.84- 5.01mg/kg, the detection limit meets the daily monitoring requirements of preservatives in food.

6 Precision and recovery

Operate according to the method of the present invention, add mixed standard working solution in the sample and carry out 6 parallel measurements respectively, record the mensuration repeatability of preservative content in the sample good, its RSD value is all less than 5.0%, and the rate of recovery is also 90.6%- 98.8%, among them, due to the high solubility of propionic acid in water, it affects the extraction rate of ether, and the addition of internal standard (undecanoic acid) can partially eliminate the influence of extraction rate on the quantification of propionic acid.

7 Determination of actual samples

The detection technology of the present invention is used to measure the content of preservatives in several types of food on the market.

Example 1

Determination of preservatives in soy sauce

Weigh 5.00g of soy sauce (accurate to 0.01g) into a 125mL separatory funnel, add 10mL of saturated NaCl aqueous solution and 1.0mL of hydrochloric acid solution and mix well, then add 1.0mL of undecanoic acid internal standard solution, and then use 50mL, 30mL, 30mL of Extract three times with diethyl ether, combine the ether layers, wash with 30mL saturated NaCl aqueous solution until neutral, dehydrate through anhydrous sodium sulfate, concentrate in a water bath at 40±2°C to 0.3-0.5mL, blow dry with nitrogen, and dilute to 5.0 mL with acetone mL. After the sample liquid passes through a 0.45 μm filter membrane, it enters the gas chromatograph for determination, and the spectrogram is shown in Figure 2. The soy sauce contains 0.034 g/kg propionic acid, 0.010 g/kg dimethyl fumarate, and 0.082 g/kg dehydroacetic acid. kg, sorbic acid 0.67g/kg, benzoic acid 0.40g/kg.

Example 2

Determination of preservatives in orange juice beverages

Weigh 10.00g of orange juice drink (accurate to 0.01g) into a 125mL separatory funnel, add 10mL saturated NaCl aqueous solution and 1.0mL hydrochloric acid solution and mix well, then add 1.0mL undecanoic acid internal standard solution, and then use 50mL, 30mL, Extract three times with 30 mL of diethyl ether, combine the ether layers, wash with 30 mL of saturated NaCl aqueous solution to neutrality, dehydrate through anhydrous sodium sulfate, concentrate in a water bath at 40±2°C to 0.3-0.5 mL, blow dry with nitrogen, and dilute to 0.3-0.5 mL with acetone. 5.0mL. After the sample liquid passes through a 0.45 μm filter membrane, it enters a gas chromatograph for determination, and the spectrogram is shown in Figure 3. The beverage contains 0.10 g/kg of benzoic acid.

Example 3

Determination of preservatives in vinegar

Weigh 7.00g vinegar (accurate to 0.01g) into a 125mL separatory funnel, add 10mL saturated NaCl aqueous solution and 1.0mL hydrochloric acid solution and mix well, then add 1.0mL undecanoic acid internal standard solution, and then use 50mL, 30mL, 30mL Extract three times with diethyl ether, combine the ether layers, wash with 30mL saturated NaCl aqueous solution until neutral, dehydrate through anhydrous sodium sulfate, concentrate in a water bath at 40±2°C to 0.3-0.5mL, blow dry with nitrogen, and dilute to 5.0 mL with acetone mL. After the sample liquid passes through a 0.45 μm filter membrane, it enters a gas chromatograph for determination, and the spectrogram is shown in Figure 4. The vinegar contains 0.42 g/kg of propionic acid and 0.075 g/kg of dimethyl fumarate.

Example 4

Determination of Preservatives in Egg Yolk Crisp

Weigh 10.00g (accurate to 0.01g) of egg yolk crisps into a 100mL volumetric flask, add water and soak in a water bath at 80±2°C for 30 minutes, take it out and cool to room temperature, add water to volume, filter, take 20.0mL of the filtrate into a 125mL separatory funnel, add Mix 10mL saturated NaCl aqueous solution and 1.0mL hydrochloric acid solution, then add 1.0mL internal standard solution, then extract three times with 50mL, 30mL, and 30mL diethyl ether, combine the ether layers, wash with 30mL saturated NaCl aqueous solution until neutral, wash through anhydrous Dehydrate with sodium sulfate, concentrate in a water bath at 40±2°C until nearly dry, blow dry with nitrogen, and dilute to 5.0 mL with acetone. The sample liquid was passed through a 0.45 μm filter membrane and entered into a gas chromatograph for determination. The spectrogram is shown in Figure 5. The egg yolk cake contained 0.12 g/kg of sorbic acid and 0.065 g/kg of benzoic acid.

8 summary

The detection method established by this invention has the advantages of one-time detection of many kinds of preservatives, good linearity, high detection sensitivity (detection limit is 0.84-5.01mg/kg), good anti-specificity (precision is 1.9-4.3%, recovery rate is in 88.9-101.6%), easy to operate, resistant to matrix interference, and reliable results, suitable for accurate determination of various preservatives in food, providing strong technical support for food quality supervision.

Claims (2)

1. A gas chromatography detection method for various preservatives in food is carried out according to the following steps:

1) preparing a sample extracting solution:

preparing liquid sample extracting solution: weighing 5-10g of a liquid sample in a 125mL separating funnel, adding 10mL of saturated NaCl aqueous solution and 1.0 part of hydrochloric acid solution for acidification, uniformly mixing, adding 1.0mL of internal standard solution, extracting with diethyl ether for three times, combining ether layers, washing with saturated NaCl aqueous solution to be neutral, and dehydrating the ether layer with anhydrous sodium sulfate for later use; or,

preparing a solid sample extracting solution: weighing 5-10g of solid sample in a 100mL volumetric flask, adding water, soaking and extracting in water bath at 80 +/-2 ℃ for 30-60min, taking out, cooling to room temperature, adding water to a constant volume of 100mL, filtering, and taking 10.0-25.0mL of filtrate in a 125mL separating funnel; adding 10mL of saturated NaCl aqueous solution and 1.0mL of hydrochloric acid solution, mixing uniformly, adding 1.0mL of internal standard solution, extracting with ethyl ether for three times, combining ether layers, washing with saturated NaCl aqueous solution to be neutral, and dehydrating the ether layers by using anhydrous sodium sulfate for later use;

2) and concentrating: rotationally concentrating the above sample extractive solution in 40 + -2 deg.C water bath to 0.3-0.5mL, blow-drying with nitrogen, diluting with acetone to 2.0-5.0mL, and filtering with 0.45 μm filter membrane to be measured;

3) and computer detection: inputting the liquid to be detected into a gas chromatograph equipped with a hydrogen flame detector for detection; the chromatographic conditions are as follows:

column temperature: the initial temperature is 130 ℃, the temperature is increased to 170 ℃ at the speed of 10 ℃/min, the temperature is kept for 3min, the temperature is increased to 260 ℃ at the speed of 20 ℃/min, and the temperature is kept for 21.5 min;

the various preservatives are propionic acid, sorbic acid, benzoic acid, dehydroacetic acid, methyl paraben, ethyl paraben, propyl paraben, isopropyl paraben, butyl paraben, isobutyl paraben, heptyl paraben, and dimethyl fumarate;

the hydrochloric acid used for acidification in the step 1) is mixed solution prepared by equal volume of concentrated hydrochloric acid with the concentration of 12moL/L and water;

the components of the internal standard solution in the step 1) are undecanoic acid and acetone, and the content of the undecanoic acid is 1-2 mg/mL.

2. The gas chromatography detection method for preservatives in food according to claim 1, characterized in that the ether is used for extraction 3 times in step 1), and the volumes of the ether used in sequence are 50mL, 30mL and 30 mL.

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