GB 31604.45-2016Food contact materials for export -- Polymer materials -- Determination of isocyanates by high performance liquid chromatography (English PDF)

3.1 Reagents

3.1.1 Dichloromethane (CH2Cl2). it shall be dried by 5A molecular sieves, stay for

overnight for standby application.

3.1.2 Ethyl ether (C2H6O).

3.1.3 Phosphoric acid (HPO3).

3.1.4 Acetonitrile (C2H3N). chromatographic purity.

3.4 Preparation of the standard solution

3.4.1 Isocyanate stock solution (1000 mg/L). weigh and take 0.01 g (accurate to 0.1

mg) of various isocyanate standard materials; dissolve the dichloromethane; then

transfer it to a volumetric flask of 10 mL; dilute the dichloromethane to the constant

volume. Stock solution shall be stored at -20 °C under dry preservation; it shall be kept

from the light. The term of validity is 1 month.

3.4.2 Standard intermediate-solution of isocyanate (100 mg/L). respectively weigh and

take 5mL of dichloromethane in six 10 mL volumetric flasks; respectively transfer them

into various 1.0 mL of isocyanate stock solution; dilute them to the constant volume

with dichloromethane. The standard intermediate-solution shall be stored at -20 °C

under dry preservation; it shall be kept from the light. The term of validity is 1 month.

3.4.3 Standard working solution of Isocyanate (1 mg/L). respectively weigh and take

5mL of dichloromethane into six 10mL volumetric flasks; respectively add 100 µL of

various standard intermediate-solutions of isocyanate; dilute them to the constant

volume with dichloromethane; mix them evenly. Standard working solution shall be

stored at -20 °C under dry preservation; it shall be kept from the light. The term of

validity is 2 weeks.

3.4.4 Standard working solution of mixed isocyanate. respectively weigh and take 5

mL of dichloromethane into six 10 mL volumetric flasks; successively add 0.00 mL,

0.01 mL, 0.05 mL, 0.10 mL, 0.25 mL and 0.50 mL of various standard intermediate-

solutions of isocyanate; dilute them to the constant volume with dichloromethane; mix

them evenly; the mixed standard working solutions whose isocyanate's concentration

are respectively 0 mg/L, 0.10 mg/L, 0.50 mg/L, 1.0 mg/L, 2.5 mg/L and 5.0 mg/L can

be acquired. These mixed standard working solutions shall be stored at -20 °C under

dry preservation; they shall be kept from the light. The term of validity is 2 weeks.

4.1 Liquid chromatograph. configure the fluorescence detector.

4.2 Glass bottle. 20 mL, with PTFE cap; it should be dried before use.

4.3 Aqueous filter membrane. 0.45 µm.

4.4 pH meter.

4.5 Analytical balance. the sensitivity shall be 0.0001 g and 0.01 g.

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