GB/T 30647-2014Determination of harmful elements total content of coatings (English PDF)

6.1 Preparation of coating film

Stir the sample to be tested evenly. Prepare a mixed sample according to the product's stated ratio (no need to add a diluent). After mixing well, prepare a coating film of appropriate thickness on a glass plate or Teflon plate (see 5.12).

6.2 Preparation of test solution

6.2.1 General

6.2.1.1 This standard provides the following three test solution's preparation

The laboratory may choose one of them according to the conditions.

6.2.2 Dry ashing method

Weigh about 2 g (accurate to 0.1 mg) of the crushed sample. Put it into the crucible (see 5.8). Place the crucible on a hot plate (see 5.5) in a fume hood.

Gradually increase the temperature of the hot plate (not exceeding 475 °C), until the sample is digested into a coke; meanwhile the volatile digestion products have been fully discharged, leaving only dried residue. Then put the crucible in a muffle furnace at (475 ± 25) °C and keep it warm until it is completely ashed.

6.2.3 Wet acid digestion

Weigh about 0.5 g ~ 1 g of the crushed sample (accurate to 0.1 mg). Place it in a 50 mL beaker (see 5.10). Add 7 mL of nitric acid (see 4.1). Cover the watch glass. Heat it on a hot plate (see 5.5) to keep the solution slightly boiling for about 5 ~ 15 min. Continue to heat until white smoke is generated, but it cannot be dried. Remove the beaker from the hot plate.

6.2.4 Microwave digestion

Weigh about 0.1 g ~ 0.2 g (accurate to 0.1 mg) of the crushed sample and place it in a microwave digestion tank. Add 6 mL of nitric acid (see 4.1) and 1 mL ~ 2 mL of hydrogen peroxide (see 4.4). After the reaction is stable, close the digestion tank and place it in a microwave digestion instrument (see 5.6). Set appropriate digestion conditions for digestion.

6.3 Testing

6.3.1 General

For the test solution prepared in accordance with 6.2, use appropriate analytical instrument (see 5.1) to determine the content of the tested elements.

When using any kind of analytical instrument for measurement, the analyst shall operate it in accordance with the instrument manual or operation manual; indicate the analytical instrument used in the test report.

8.1 Repeatability

The relative deviation of the two test results of the same operator shall be less than 10%. […]