Abstract : Liquid milk is a nutritious food that is commonly used by the public. It is often packaged in black and white film. During the packaging process or when unpacking, occasionally it will smell like paint, which is caused by the residual organic solvent in the bag. In this paper, the GC-7800 gas chromatograph is used to test the solvent residue of the packaging bag, and the principle, equipment parameters and testing process of the equipment are described. It has certain guiding significance for the enterprises that are troubled by the packaging odor problem.

Key words : dairy products, liquid milk, black and white film, solvent residue, odor, printed film, gas chromatograph

1 , meaning

Liquid dairy products are used as nutritious foods for the general public. The safety quality directly affects the health of consumers. Liquid milk often has bitter taste, flocculent precipitation, and mold growth in the milk bag during the shelf life. The odor is packaged. The odor is similar to the smell of paint or other chemical agents. In severe cases, odor will migrate to the dairy product, making the dairy product inedible. The main reason for the appearance of odor is that the black and white film used in liquid milk generally adopts a surface printing process, that is, a special water-resistant and high-temperature resistant surface printing ink is printed on the outer surface of the black and white film packaging. At the same time, the resin raw materials and inks used in the manufacturing process and printing process of black and white film are prone to harmful small molecular substances or organic solvent residues. Therefore, dairy companies should strengthen the detection of solvent residues in liquid black and white film packaging.

Figure 1 liquid milk black and white film packaging

2 , the implementation of standards

The test can reference GB / T 10004-2008 "plastic composite packaging films, bags dry lamination, extrusion lamination" method of detecting the residual solvent standards.

3 , test samples

Black and white film bags from a dairy factory.

4 , test equipment

LabthinkInstrumentsCo Technology Co. of G C - 7800 gas chromatograph.

FIG 2 G C - 7800 gas chromatograph

4.1 Test principle

Gas Chromatograph is a separation and analysis tool for multi-component mixtures. It uses inert gas as the mobile phase and uses column separation technology. When multiple analytes enter the column, the flow coefficients of the components in the column are different due to the different partition coefficients of the components in the column. After a certain column length, the mixed components leave the column separately. After entering the detector, after being detected, it is converted into an electrical signal and sent to the data processing workstation, thereby completing the detection and analysis of the tested substance.

4.2 Scope of application

(1) Solvent residue: It is suitable for solvent residue analysis and testing of various food, pharmaceutical packaging plastic film, paper-plastic composite film, cigarette package and other materials.

(2) Purity analysis: It is suitable for the purity analysis of various solvents for packaging printing.

(3) Moisture analysis: It is suitable for the analysis of solvent moisture content in the packaging and printing industry.

(4) Special accessories or modifications are required to expand and apply to the analysis of vinyl chloride monomer content

4.3 Equipment parameters

• The instrument is capable of constant temperature and temperature programmed operation. The column chamber is equipped with a flexible rear door automatic temperature control system, which can realize the near-room temperature operation in the true sense. The temperature control range of the column chamber is room temperature +3 °C ~ 400 °C , the temperature control accuracy is better than ±0.1 °C , the deviation between the set temperature and the display temperature is not more than 1 °C , the deviation between the set temperature and the actual temperature. Not more than 2% .
• The instrument can be programmed for temperature rise, the temperature rise order is 5 steps , the heating rate is 0.1 ~ 30 °C / min , and the repeatability of the program temperature is not more than 2% .
• The temperature control accuracy of the gasification chamber and the detection chamber in the temperature range of +15 °C to 200 °C is ±0.1 ° C , and the temperature control accuracy is ±0.2 ° C when the temperature is greater than 200 ° C .
• The basic configuration of the instrument is a hydrogen flame ionization detector (FID ) with a detection limit of no more than 2 × 10 ^-11 g/s ( benzene ) , a noise of no more than 0.025 mV , and a drift of no more than 0.15 mV/h .
• The detector adopts a unitized combination design and adopts a plug-and-play extended control mode. The hydrogen flame detector and the thermal conductivity detector are arranged, and the configuration can be selected according to the needs of the user analysis. The instrument can be installed with four detectors at the same time.
• The injection system is available with a variety of injection devices such as packed column head injection, capillary column split / splitless injection with diaphragm cleaning .
• The response signal can reach a wide range of 1500 mV with good consistency and can meet the needs of high-purity sample analysis.
• Excellent performance column oven, the detector and in the case of the gasification chamber are 200 ℃ can be achieved at room temperature +3 ℃ operation near room temperature, and the instrument has a good reproducibility of temperature-programmed to ensure that the complex components of the sample analyzed Reserved Time consistency.
• The instrument has a high temperature protection function. If any temperature control exceeds the set temperature within a certain range (set value is 20 °C ), the instrument will be powered off and alarmed. The instrument has a low pressure and gas shutoff protection function for the carrier gas path.
• The unique operation and control system software and hardware design, the instrument automatically implements the whole process software monitoring during the operation process, which fundamentally eliminates the phenomenon that the instrument temperature and operating parameters are out of control. It realizes no “ fault ” over-temperature protection, as well as a unique active over-temperature protection function and dual hardware self-locking over-temperature control structure to ensure the safe operation of the instrument when unattended.

5 , the test process

(1) Set the test parameters. After clicking Start, the GC-7800 gas chromatograph starts the baseline balance.

(2) After the baseline of the instrument is stable, mix the mixed standards of different concentrations, inject them into the sealed headspace bottle, and place them in a constant temperature room at 80±2 °C for 30 min .

(3) Take a certain amount of standard sample gas from the above-mentioned headspace bottle with a sampling needle, and quickly inject it into the chromatograph, or configure the autosampler to automatically inject. A standard curve of the peak area of ​​each reference material and the corresponding concentration is plotted.

(4) A sample was 0.2 m ² quickly cut 10 mm × 30 mm pieces and placed in a clean preheated under conditions of 80 ± 2 ℃ flask, quickly sealed, placed in a greenhouse 80 ± 2 ℃ constant Place it for 30 min . Note that the sample should be protected from contamination during the sample preparation process.

(5) Take a sample gas from the thermostated sample bottle with a sampling needle, quickly inject it into the chromatograph, or configure the autosampler to automatically inject.

(6) The concentration of the component is read from the standard curve of the corresponding component based on the peak area of ​​the sample.

6 , test results

The total amount of solvent residues of the liquid milk packaging sample for black and white film was 7.5792 mg/m ² , and the benzene type was 0.1411 mg/m ² .

7 , conclusion

From the above test results, refer to GB/T 10004-2008 "Packaging plastic composite film, bag dry composite, extrusion compounding" in the solvent residue is the total solvent residue ≤ 5.0 mg / m ² , of which benzene The solvent should not be detected (< 0.01 mg/m ² ) , so the total solvent residue of the sample tested in this paper exceeded the standard, and the odor of the sample was mainly caused by the high residual solvent. GC-7800 gas chromatograph has the advantages of high test accuracy, good accuracy and safe use in testing solvent residue. It can truly reflect the hygienic chemical properties of packaging materials and help dairy companies solve the problem of packaging odor. In addition to black and white film, GC-7800 gas chromatograph can also be used to test solvents in plastic composite film, aluminum-plastic composite film, aluminum-plated composite film, paper-based composite film, printed single-layer film and other packaging materials. Residual amount. Labthink has been committed to providing professional inspection services and equipment to customers around the world. Over the years, it has provided thousands of solvent residue testing services to customers around the world, providing customers with reliable technical solutions. Labthink is looking forward to enhancing technical exchanges and cooperation with users in various industries.

Electric Backrest

Electric Backrest(Adjustable Bed Back Rest) is a very useful equipment for patient,it can support elders and users in a seated position in bed for eating, reading or watching TV easily. Household Medical Equipment is designed specially for elderly people, which could also help ease burden when taking care of the elderly.Electric Mobility Aid to Sit Up in Bed.

Electric Backrest,Adjustable Bed Back Rest, Electrical Back Rest ,Electric Mobility Aid to Sit Up in Bed

Haloxylon Ammodendron Medical Equipment Co., Ltd. , https://www.ssmedicaldevic.com