GB 31604.21-2025 National Food Safety Standard Determination of Migration of Benzoic Acid, Phthalic Acid, and Benzoic Acid in Food Contact Materials and ProductsIt is sponsored by the National Health CommissionIn collaboration with the State Administration for Market RegulationImportant national standards jointly releasedOfficially released on September 2, 2025And fromImplemented from March 2, 2026.

1、 Scope of application compared to the old version

（1） Scope of application

This standard is applicable toVarious food contact materials and products, includingPlastic materials and products、Paper and cardboard materials and products、adhesive、Coatings and CoatingsWait.

（2） Comparison of old versions

1. Name change:The new standard will be named by《GB 31604.21-2016National food safety standard - Determination of terephthalic acid migration in food contact materials and productsHow to translatemodify to《GB 31604.21-2025

National Food Safety Standard - Determination of Migration of Benzoic Acid, Phthalic Acid, and Benzoic Acid in Food Contact Materials and Products；2. Newly added test substance:The new standard is based on the originalterephthalic acidOn the basis of detection, new additions have been madebenzoic acid、Phthalic acid(1,2-phthalic acid)isophthalic acid(1,3-phthalic acid)Trimesic acid(1,3,5-Benzenetricarboxylic acid)Trimellitic acid(1,2,4-Benzoic acid) and

3.Phthalic acidDetermination of migration amounts of six substances, including 1,2,3-benzenetricarboxylic acid;

Optimization of analysis steps:The new standard has comprehensively revised and optimized the analysis steps, making it more suitable for the needs of simultaneous analysis of multiple components. These modifications include:

(1) Improvement of sample pretreatment processEnable it to simultaneously extract and separate multiple target analytes;

(2) Optimization of detection conditionsTo effectively separate different acidic substances with similar structures;

(3) Standardization of result expression

Ensure the consistency and comparability of the results of various substance measurements.

2、 Operation process

（1） Migration ExperimentThis step aims to simulate the process of target substance migration from food contact materials to food under actual usage conditions.

1. Experimental basis:Strictly follow the provisions of GB 31604.1 (General Requirements) and GB 5009.156 (General Principles for Migration Test Preparation).

2. Selection of food simulants:Select appropriate food simulants based on the expected usage conditions of the product, such as the type of food in contact, temperature, and time. Common simulants include: (1) water-based food simulants (such as 4% acetic acid, 10% ethanol solution, etc.); (2) Alcoholic simulants (such as 95% ethanol); (3) Fat mimetics (such as olive oil, isooctane).

3. Sample preservation:

If the soaking solution obtained after the migration experiment cannot be immediately detected, it should be stored in the dark at 0 ℃ to 4 ℃, and the storage period should not exceed 3 days. Before proceeding to the next step of testing, the soaking solution needs to be restored to room temperature.

（2） Sample pre-treatment

The purpose of this step is to prepare the target analyte in the soaking solution into a solution suitable for instrument analysis. The processing methods vary depending on the type of simulated object.Regarding the treatment of olive oil soaking solution:

(1) For phthalic acid and trimeric acid:Accurately weigh 5.0 grams of olive oil soaking solution, add 5 milliliters of n-hexane, vortex and mix well. Then add 10 milliliters of 50% (volume fraction) ethanol solution, vigorously vortex and oscillate for extraction, and then centrifuge. Remove the clear liquid (lower layer) and filter it through a microporous membrane before testing;

(2) For benzoic acid:Accurately weigh 10.0 grams of olive oil soaking solution, add 10 milliliters of acetonitrile, vortex and shake for extraction, centrifuge, and filter the supernatant for testing.

2. Treatment of 95% ethanol immersion solution:Dilute the volume fraction of ethanol with an appropriate amount of water to below 50%, and then proceed with instrument analysis.

3. Treatment of water-based food simulants (such as 4% acetic acid, 10% ethanol, etc.) and iso octane soaking solution:

These soaking solutions can generally be directly injected for measurement, or diluted appropriately according to the expected concentration before sampling.

（3） Instrument analysis

Use high-performance liquid chromatography to separate and quantitatively detect the processed samples.1. Analysis conditions:

(1) Chromatographic column:Recommend using C18 reverse phase chromatography column.

(2) Mobile phase:Composed of 0.1% phosphoric acid aqueous solution and acetonitrile, a gradient elution program was used to achieve effective separation of 7 target substances.

(3) Detector:Using a UV detector or diode array detector, the detection wavelength is usually set to 230 nm.

(4) Column temperature:

Usually set at 40 ℃.

2. Quantitative methods:

(1) Quantification using external standard method.

(2) Firstly, use a series of mixed standard working solutions with known concentrations for injection analysis, and plot a standard curve with concentration as the x-axis and peak area (or peak height) as the y-axis.(3) Secondly, under the same conditions, the processed sample solution is injected for analysis to obtain the chromatographic peak area of the target substance.(4) Finally,

Take the sampleSubstitute the peak area into the standard curve to calculate the concentration of each target analyte in the sample.

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4） Result calculation

Based on the concentration obtained from instrument analysis, the volume (or mass) of the soaking solution, and the area of contact between the food contact material and the soaking solution, the migration amount per unit area of each target substance is calculated using the formula provided in the standard. The calculation results are usually expressed in milligrams per square decimeter (mg/dm ²).3、 SummaryThe implementation of this national standard is to strictly monitor the harmful substances that may migrate from food contact materials at the source, ensuring that their migration amount is below the safety threshold, thereby safeguarding the long-term health of consumers.