GB/T 45275-2025Determination of N,N-dimethylformamide in toys and children's products — Gas chromatography-mass spectrometry (English PDF)

5.2 N, N-Dimethylformamide standard substance (CAS No. 68-12-2). purity >=99%, or

with certified standard certificate, as per Annex A.

5.3 N, N-dimethylformamide standard stock solution. Accurately weigh an appropriate

amount of N, N-dimethylformamide standard substance (accurate to 0.1 mg). Use ethyl acetate (5.1) to prepare a standard stock solution with a mass concentration of 100 mg/L.

NOTE. The standard stock solution shall be stored at 0°C~8°C away from light. The validity period is 1 month.

5.4 N, N-dimethylformamide intermediate standard solution. Accurately pipette an

appropriate amount of N, N-dimethylformamide standard stock solution (5.3). Use ethyl acetate (5.1) to prepare an intermediate standard solution with a mass concentration of 20 mg/L.

NOTE. The intermediate standard solution shall be stored at 0°C~8°C away from light. The validity period is 1 month.

5.5 N, N-dimethylformamide standard working solution. Take appropriate amount of

N, N-dimethylformamide intermediate standard solution (5.4). Dilute with ethyl acetate (5.1) to prepare a series of standard working solutions with mass concentrations of 0.5 mg/L, 1 mg/L, 2 mg/L, 5 mg/L, and 10 mg/L respectively.

NOTE. The standard stock solution shall be stored at 0°C~8°C away from light. The validity period is 1 month.

6.3 Ultrasonic extractor. with temperature control device; upper temperature limit

>=60°C; the performance of ultrasonic extractor shall be in accordance with 6.13 of GB/T 22048-2022.

6.4 Organic filter membrane. pore size is 0.22 µm.

6.5 Gas chromatography-mass spectrometry (GC-MS). equipped with EI source.

7.1 Sample preparation and extraction

Obtain the single material from the sample by mechanical means. Use suitable tools to shape the sample into a size not exceeding 5 mm.

Use an analytical balance (6.1) to weigh 1 g (accurate to 0.1 mg) of sample. Place it in a stoppered extraction bottle (6.2). Add 20.0 mL of ethyl acetate solvent (5.1) and tighten the bottle cap. Place the sample in an ultrasonic extractor (6.3) in a 60°C water bath and ultrasonicate for 30 min. After cooling, filter the extract through an organic filter membrane (6.4). Use a gas chromatograph-mass spectrometer (6.5) to measure the extract).

7.2 Blank test

Except for not weighing the specimen, the remaining steps are the same as 7.1 to carry out a blank test.

7.3 Instrument analysis conditions

Since the test results depend on the instrument used, it is not possible to give universal parameters for chromatographic analysis. The parameters shall be set to ensure that the component being measured can be separated from other components to a limited extent during the determination. The following operating conditions have been proven to be suitable for the test.

a) Capillary column. polar polyethylene glycol stationary phase, 30 mx0.25 mmx0.25 µm;

b) Injection volume. 1 µL;

c) Injection port temperature. 230°C;

d) Chromatographic mass spectrometer interface temperature. 250°C;

e) Transfer line temperature. 250°C;

f) Column temperature. 50°C for 2 min; 20°C/min to 200°C, for 2 min;

g) Injection system. non-divided flow;

h) Carrier gas. helium;

i) Carrier gas flow rate. 1.2 mL/min;

j) Ionization mode. EI ionization;

k) Ionization energy. 70 eV;

l) Ion source temperature. 230°C;

m) Solvent delay. 2 min;

n) Scan mode. full scan mode and selected ion monitoring; mass scanning range is 30 amu~100 amu; quantification ion is 73; qualification ions are 44, 42, 72, 74.

7.4 Drawing of standard working curve

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