GB/T 43276-2023Determination of formamide emission from toy materials (English PDF)

3.1 Formamide emission

Mass of formamide emitted from the sample within a specified time and space.

3.2 Emission test chamber

A test equipment that is composed of a chamber, an air circulation device, an air exchange device, an air purification device, a temperature and relative humidity control device, a monitoring device, etc., has controlled operating parameters and is used to […]

5.3 Formamide for gas chromatography calibration

5.3.1 Standard gas

Prepare standard gas containing formamide gas with a mass concentration of about 100 µg/m3, or purchase certified standard gas.

5.3.2 Standard solution

Accurately weigh 0.1 g (accurate to 0.1 mg) of formamide standard substance (5.1), dissolve it in methanol (5.2) and make up to 100 mL to prepare a standard stock solution with a mass concentration of 1000 µg/mL. The standard stock solution can be stored in a sealed container at 0 °C ~ 4 °C refrigerator for 3 months.

Pipette an appropriate volume of the standard stock solution, prepare a standard series of solutions with methanol (5.2). Prepare solutions with mass concentrations of 10 µg/mL, 100 µg/mL, and 1000 µg/mL to become the formamide standard solutions. It can also purchase certified formamide standard solutions.

5.4 Adsorbent

Poly 2,6-diphenylene oxide (Tenax TA), particle size 0.18 mm ~ 0.25 mm (60 mesh ~ 80 mesh). The adsorbent shall be heated and activated with an inert gas flow at its highest use temperature for at least 18 h before being loaded into the tube. To prevent secondary contamination, the adsorbent shall be cooled, stored, and piped in clean air.

Other adsorbents can be selected with reference to ISO 16000-6:2021 and shall be verified before use.

5.5 Inert gas

High-purity nitrogen. purity not less than 99.99 %. High-purity helium. purity not less than 99.999 %.

6.1 Emission test chamber

It shall comply with GB/T 31107-2014 or other equivalent emission test chambers.

The emission test chamber consists of a sealed cabin with an effective volume of 50 L ~ 1000 L (preferably 60 L), an air purification system, an air temperature and humidity control system, a temperature and humidity monitoring system, an air flow control device, an air sampling system, etc., as shown in Figure 1.

6.4 Air sampler

The flow range is 0.02 L/min ~ 0.5 L/min. The flow is stable and adjustable. The sampling flow shall be calibrated with a flow meter before and after sampling, with an error of less than 5 %. A sampler with automatic flow control compensation function can also be used. The sampling flow shall be calibrated with a flow meter regularly, with an error of less than 5 %.

6.5 Flow meter

Soap film flow meter or electronic flow meter, used for gas flow calibration of air sampler.

6.6 Thermometer

The accuracy is 0.5 °C.

6.7 Atmospheric pressure gauge

The accuracy is 0.01 kPa.

6.8 Gas chromatograph (GC)

Equipped with mass spectrometer (MS) or other suitable detectors.

6.9 Thermal desorption instrument (TD)

It can perform secondary thermal desorption on the sampling tube and bring the desorbed gas into the gas chromatograph through inert gas.

A typical secondary thermal desorption system shall include devices for purging inert gas at the same time, such as a fixed sampling tube and a heated sampling tube, and a cold trap for concentrating and secondary thermal desorption of the sample. The desorption temperature, desorption time and carrier gas flow can all be adjusted.

7.1 Storage

After the sample arrives at the laboratory, the sample shall be stored in an indoor environment at (25 ± 5) °C and stored in packaging.

7.2 Preparation

During sample preparation, the test environment shall be kept clean and ventilated to avoid sample contamination. The area loading factor L of the sample is calculated according to formula (1) to ensure that its area loading factor is (0.4 ± 0.02) m²/m3.The area loading factor of the sample shall be calculated based on the exposure state of the - relative humidity (50 ± 5) %;

- air exchange rate (0.5 ± 0.01) times/h;

- air velocity on the sample surface 0.1 m/s ~ 0.3 m/s;

- area loading factor (0.4 ± 0.02) m²/m3.

8.2 Preparation of emission test chamber

8.2.1 Clean the emission test chamber before test. It is advisable to use alkaline cleaning agent (pH >= 7.5) to clean the inner wall of the chamber, and then use grade 3 water that meets the requirements of GB/T 6682 to scrub the inner wall of the chamber 2 ~ 3 times, open the door, and turn on the fan until the chamber is air-dried.

8.2.2 High-temperature cleaning can also be used to clean the sealed cabin space with cleaned air to ensure that the temperature of all inner surfaces in contact with the atmosphere of the sealed cabin space exceeds 180 °C. After reaching the heating temperature, the air is repeatedly ventilated and cleaned for 4 h to reduce the concentration of residual pollutants in the sealed cabin space.

8.2.3 After cleaning, close the cabin door and operate the emission test chamber according to the conditions specified in 8.1. After reaching the test conditions, measure the background concentration of the emission test chamber.

8.2.4 The next test can be carried out only when the background mass concentration of formamide in the chamber is not greater than 6 µg/m3.

8.3 Balance of the sample

8.3.1 Place the sample prepared according to 7.2 and 7.3 in the center of the emission test chamber. For products that are used with one side exposed, the sample is placed horizontally at the bottom of the emission test chamber, and the emitting surface shall be horizontally upward; for products that are used with full exposure, the sample is placed on a stainless steel bracket. Ensure that the air flow passes evenly over the surface of the sample, and quickly close the emission test chamber door to start the test.

8.3.2 The time when the sample is placed in the emission test chamber is taken as time 0.

8.4 Air sampling in the chamber

8.4.1 After the sample is balanced in the emission test chamber for (72 ± 1) h, the air sampling analysis in the chamber is carried out. All air sampling shall be completed within 1 h.

8.4.2 Open the sampling tube at the sampling location and connect it directly to the air outlet of the emission test chamber. Open the air sampler (6.4) and extract 1 L ~ 5 L of air in the chamber at a flow rate of 0.02 L/min ~ 0.5 L/min. The sampling flow rate shall not be greater than 80 % of the air flow supplied to the emission test chamber.

NOTE 1: The sampling volume is determined according to the formamide emission from the sample.

Under the test conditions of this document, a sampling volume of 3 L can meet the test of most samples.

NOTE 2: The laboratory shall pay attention to the possibility of penetration in the adsorption tube when the formamide emission is too high. If necessary, the sampling volume shall be reduced or the adsorption tubes shall be connected in series for sampling.

8.4.3 The sampling tube shall be sealed after sampling, and the temperature and atmospheric pressure at the time of sampling shall be recorded. To avoid possible changes, the analysis should be completed within 4 weeks after sampling.

8.5 Field blank collection

According to the steps specified in 8.4, it is carried out simultaneously at the sampling site, including removing and re-covering the nut, but the actual gas sampling volume is 0 L.

9.1 Sample desorption conditions

Select the temperature, time and gas flow rate of thermal desorption so that the thermal desorption efficiency of formamide is above 95 %. Since the requirement for achieving thermal desorption efficiency is related to the instrument used, the set parameters shall ensure the thermal desorption efficiency of formamide. The reference working conditions for thermal desorption are shown in A.1 in Annex A.

9.2 Chromatographic analysis conditions

Since the test results are related to the instrument used, it is impossible to give universal parameters for gas chromatography. The principle of setting parameters is to obtain the best separation effect in the shortest time. The reference working conditions for chromatographic analysis are shown in A.2.

9.3 Plotting of standard curve

9.3.1 Gas external standard method

Use a pump to accurately extract 200 mL, 500 mL, 1 L, 2 L, 5 L, 10 L, 20 L of the standard gas specified in 5.3.1 to the sampling tubes as the standard series.

9.3.2 Liquid external standard method

A.1 Desorption conditions

The thermal desorption reference working conditions for determination of formamide emission are as follows.

a) thermal desorption temperature. 250 °C.

b) thermal desorption time. 5 min.

c) thermal desorption gas flow rate. 20 mL/min ~ 50 mL/min.

d) cold trap. maximum temperature is 300 °C, minimum temperature is -30 °C.

e) adsorbent. the same as the adsorbent in the sampling tube, 40 mg ~ 100 mg.

f) transmission line temperature. 180 °C.

g) split ratio. the split ratio between the sample tube and the secondary cold trap and between the secondary cold trap and the analytical column shall be selected according to the mass of volatile organic compounds in the sampling tube.

Considering the molecular characteristics of formamide, a lower split ratio should be used.

A.2 Chromatographic analysis conditions

The chromatographic analysis reference working conditions for determination of formamide emission are as follows.

a) chromatographic column. DB-WAX (30 m × 0.25 mm × 0.25 µm) capillary column or equivalent.

b) chromatographic column temperature. programmed temperature rise, the initial temperature is 50 °C, hold for 2 min, then programmed temperature rise to 200 °C at a rate of 30 °C/min, hold for 3 min.

c) chromatography-mass spectrometry interface temperature. 250 °C.

d) ion source temperature. 200 °C.

e) carrier gas. helium, 1.0 mL/min.

f) ionization mode. EI. […]