Analysis method of polyethylene food bottle hygiene standard

This standard applies to the use of polyvinyl chloride resin for food packaging as the main raw material, according to a specific formula with non-toxic or low toxicity plasticizers, stabilizers and other additives processed by the method of rolling or blow molding, for each A variety of sweets, pastries, cookies,
Determination of hygienic indicators for molded products such as packaging of foods such as loaves, pickles, cold soups, and seasonings, and gaskets for beverage bottles.

1 appearance inspection

Normal color, no smell, foreign body.

2 sampling methods

According to the manufacturer's product batch number (same recipe, same raw material, same process, same specification as one batch), each batch of samples
Ten (500 ml/piece, less than 500 ml/piece, sample doubled accordingly) or 1 meter long, indicating product name, batch number, and sampling date, respectively. Half of them are for testing, and only half of them are for storage for two months in preparation for arbitration analysis.

3 sample processing

3.1 Sample Pretreatment: Wash the sample with detergent, rinse it with tap water, rinse it with water three times and dry it.
3.2 Soaking conditions: The amount of soaking liquid is calculated with 2ml soaking solution of 1cm2 sample.
3.2.1 Water: 60 °C, holding 0.5h.
3.2.2 4% acetic acid: 60 °C, holding 0.5h.
3.2.3 20% Ethanol: 60°C, incubation 0.5h.
3.2.4 n-hexane: normal temperature (about 20 °C), soak 0.5h.

4 vinyl chloride monomer

4.1 Principles According to the law relating to gas shut-off, the sample is placed in a sealed balance bottle and dissolved with a solvent. At a certain temperature, the vinyl chloride monomer diffuses and reaches equilibrium, and the liquid vapor is injected into the gas chromatograph for determination.
The minimum detection limit of this method is 0.2mg/kg.
Note: This method can be used for the determination of polyvinyl chloride resin.
4.2 Reagents 4.2.1 Liquid vinyl chloride: Purity greater than 99.5%, packed in a 50 to 100 ml pressure container, and placed in a dry ice thermos bottle.
4.2.2 N,N-Dimethylacetamide (DMA): Under the same chromatographic conditions, this solvent should not detect any misalignment of the same retention values ​​as vinyl chloride. Otherwise, the aeration distills away the interference.
4.2.3 Preparation of Vinyl Chloride Standard A: Take a balance bottle, add 24.5ml DMA, weigh with stopper (accurate to 0.1mg) in a fume hood, take 1ml liquid pipette with 0.5ml of liquid vinyl chloride, quickly add the balance Dissolve in the bottle, cover and mix, then weigh and store in the refrigerator. Calculate the concentration according to equations (1) and (2):
M2 - M1
A = ———— × 1000 ... (1)
V1

M2 - M1
V1 = 24.5 + ──── .......................(2)
d
Where: A - vinyl chloride monomer concentration, mg / ml;
V1 - calibration volume, ml;
M1 - the quality of the balance bottle plus solvent, g;
M2 - the mass of M1 vinyl chloride, 9;
d - specific gravity of vinyl chloride, 0.9121 g/ml (20/20°C).
Note: In order to simplify the test, the specific gravity of vinyl chloride (20/20°C) has met the volume calibration requirement.
4.2.3 Preparation of Vinyl Chloride Standard Use Solution B: To prepare 25.0 ml with a balance bottle, determine the volume of solvent to be added based on the concentration of Solution A. The use solution B concentration was 0.2 mg/ml.

V3 = 25 - V2 .............................(3)

0.2 × 25
V2 = ───── ..........................(4)
VA
Where: V3 - to add DMA volume, ml;
V2 - take the volume of A liquid, ml;
VA - standard concentration of vinyl chloride standard A, mg/ml.
According to the calculation, first put the V3 volume DMA into the balance bottle, add the stopper, and then use a microsyringe to take the V2 volume of the A solution and inject the solvent through the rubber plug. After the mixing, the solution is B and stored in the refrigerator.
4.3 Instruments 4.3.1 Gas Chromatograph (GC): With a hydrogen flame ionization detector (FID).
4.3.2 Constant temperature water bath: 70 ±1°C.
4.3.3 Magnetic stirrer: galvanized iron wire Φ2 × 20mm is a stirring rod.
4.3.4 Grinding mouth syringe: 1, 2, 5ml, with a 5th needle, leak before use.
4.3.5 Microsyringes: 10, 50, 100 μl.
4.3.6 Balance bottle: 25±0.5ml, heat-resistant and pressure-resistant 0.5kg/cm2 glass with silicone rubber stopper.
4.4 Operation method 4.4.1 Chromatographic conditions 4.4.1.1 Column: 2m stainless steel column, internal diameter 4mm.
4.4.1.2 stationary phase: organic carrier on the test 407, 60 ~ 80 mesh (produced by Shanghai Reagent Factory, similar porapako) aging 4 hours at 200 °C.
4.4.1.3 Measurement conditions (for reference): Column temperature 100 °C, vaporization temperature 150 °C, nitrogen 20ml/min, hydrogen 30ml/min, air 300ml/min.
4.4.2 Drawing of standard curve: Prepare six balance bottles, add 3ml DMA in advance, and take 0, 5, 10, 15, 20, 25μl of B solution with micro syringes, and inject them into each bottle through the stopper. 0 ~ 5μg vinyl chloride series bottles. At the same time into a 70 ± 1 °C water bath, balance 30min. Take 2~3ml of liquid gas into the GC. Adjust the sensitivity of the amplifier (10**4x1/16~1/1 for reference) to measure the peak height and plot the peak height and mass curve.
Note: The curve range is 0~50mg/kg, which is applicable to vinyl chloride content of polyvinyl chloride resin and molded articles. Different content range curves can be plotted as needed.
4.4.3 Determination of Samples Cut the sample into fine particles, weigh 0.1 to 1g (accurate to 1mg) into the balance bottle, add a stirring bar and 3ml DMA
Immediately after the cover. Stir for 5 minutes. Other conditions are the same as in 4.4.2 "put in 70 ± 1°C.....". Measure the peak height and calculate the mass on the standard curve.
4.4.4 Calculation G×1000
X = ───────
m×1000
Where: X - vinyl chloride monomer content in the sample, mg/kg.
G - the standard curve to determine the mass of vinyl chloride, μg.
M—sample quality, g.

5 Potassium permanganate consumption

According to GB 5009.60-85 “Methods for Analysis of Hygienic Standards for Polyethylene, Polystyrene, and Polypropylene Molded Products for Food Packaging,” Chapter 3 operates.

6 Evaporation residue

According to GB 5009.60-85 Chapter 4 operation.

7 Heavy Metals

According to GB 5009.60-85 Chapter 5 operation.

8 Fading test

According to GB 5009.60-85 Chapter 6 operation.

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