GB/T 23993-2009Determination of formaldehyde content of waterborne coatings - Spectrophtometric method with acetylacetone (English PDF)

1 Scope

This Standard specifies the method for determination of formaldehyde content of waterborne coatings.

This Standard applies to the test of waterborne coatings and their raw materials with a formaldehyde content of not less than 5 mg/kg.

2 Normative references

The following documents contain provisions which, through reference in this Standard, constitute provisions of this Standard. For the dated references, their subsequent amendments (excluding corrections) or revisions do not apply to this Standard. However, the parties who enter into agreement based on this Standard are encouraged to investigate whether the latest editions of these documents are applicable. For undated reference documents, the latest editions apply to this Standard.

GB/T 601 Chemical reagent - Preparations of reference titration solutions

GB/T 3186 Paints, varnishes and raw materials for paints and varnishes - Sampling (GB/T 3186-2006, ISO 15528:2000, IDT)

GB/T 6682 Water for analytical laboratory use - Specification and test methods (GB/T 6682-2008, ISO 3696:1987, MOD)

3 Principle

Distill the formaldehyde out of the sample. In the acetic acid-ammonium acetate buffer solution with pH=6, the formaldehyde in the fraction reacts with acetylacetone under heating to form a stable yellow complex.

4 Reagents and materials

In the analytical testing, only reagents that have been confirmed to be analytically pure are used; the water used shall meet the requirements of grade

4.1 Ammonium acetate.

4.2 Glacial acetic acid. rho=1.055 g/mL.

4.3 Acetylacetone. rho=0.975 g/mL.

4.5 Iodine solution. c(1/2I2)=0.1 mol/L.

4.6 Sodium hydroxide solution. 1 mol/L.

4.7 Hydrochloric acid solution. 1 mol/L.

4.8 Sodium thiosulfate standard solution. c(Na2S2O3)=0.1 mol/L. And calibrate in accordance with GB/T 601;

4.9 Starch solution. 1 g/100 mL. Weigh 1 g of starch; use a small amount of water to mix it into a paste; pour it into 100 mL of boiling water; make it a transparent solution. Prepare it just before use;

4.10 Formaldehyde solution. About 37% (mass fraction).

5 Instruments and equipment

5.1 Distillation device. 100 mL distillation flask, serpentine condenser, distillate receiver;

5.2 Graduation tube with stopper. 50 mL (the same container as the distillate receiver in 5.1);

6 Sampling

In accordance with the provisions of GB/T 3186, take a representative sample of the product under test.

7 Test procedure

8 Expression of results

8.2 Detection limit of test method. 5 mg/kg.

9 Precision

10 Test report

The test report shall include at least the following contents. […]