GB/T 34683-2017Determination of formaldehyde content in water-borne coatings—High performance liquid chromatographic method (English PDF)

1 Scope

This Standard specifies the testing principles, reagents or materials, instruments and equipment, samples, test procedures, test data processing, detection limits and precision for the determination of formaldehyde content in water-borne coatings using high performance liquid chromatographic method.

This Standard is applicable to the determination of formaldehyde content in water-borne coatings. The determination of formaldehyde content in raw materials for water-borne coatings can also refer to this method.

2 Normative references

The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

GB/T 3186, Paints, varnishes and raw materials for paints and varnishes -- Sampling

GB/T 6682-2008, Water for analytical laboratory use -- Specification and test methods

GB/T 12807, Laboratory glassware -- Graduated pipettes

GB/T 12808, Laboratory glassware -- One mark pipettes

GB/T 23993-2009, Determination of formaldehyde content of waterborne coatings -- Spectrophotometric method with acetylacetone

3 Principle

Acetonitrile is used as the extraction solvent. Formaldehyde in the sample is extracted using a method combining ultrasonic extraction and centrifugal separation. The extract is derivatized with 2,4-dinitrophenylhydrazine under acidic conditions to form 2,4-dinitrophenylhydrazone. Use high performance liquid chromatographic method or currently effective methods that can meet accuracy requirements (such as liquid chromatography-mass spectrometry, liquid chromatography-tandem mass spectrometry, etc.) for detection. According to the standard working curve, calculate the formaldehyde content in the sample.

4 Reagents or materials

Unless otherwise specified, only reagents confirmed to be analytically pure or above and grade one water that meets the requirements of GB/T 6682-2008 are used in the analysis.

4.1 Acetonitrile: HPLC grade.

4.2 Phosphoric acid: content is greater than or equal to 85% (mass fraction).

4.3 Derivatization reagent: Weigh about 1 g (based on dry matter) of 2,4-dinitrophenylhydrazine and place it in a 100 mL brown volumetric flask (see 5.5). Dilute to the volume with phosphoric acid (see 4.2). Shake well. This solution is unstable and shall be prepared immediately before use. NOTE: 2,4-Dinitrophenylhydrazine can be further purified by recrystallization from an aqueous solution with an acetonitrile content of 25% (mass fraction).

4.4 Formaldehyde solution: content is about 37% (mass fraction).

4.5 Formaldehyde standard stock solution (formaldehyde content is about 1 g/L): Use a graduated pipette (see 5.6) to pipette 2.8 mL of formaldehyde solution (see 4.4) and place it in a 1000 mL volumetric flask (see 5.5). Dilute to the volume with water. Mix well. Calibrate its accurate concentration according to the method specified in GB/T 23993-2009. Formaldehyde standard stock solution shall be stored in the dark below 4°C. It shall be valid for 3 months. NOTE: Certified formaldehyde solution standard materials with known concentrations can also be used directly.

4.6 Formaldehyde standard solution (formaldehyde content is about 10 mg/L): Use a single-marked pipette (see 5.7) to pipette 1.0 mL of formaldehyde standard stock solution (see 4.5). Place in a 100 mL volumetric flask (see 5.5). Dilute to the volume with acetonitrile (see 4.1). Mix well. This solution is unstable and shall be prepared Weigh approximately 2.5 g of specimen (accurate to 1 mg) into a 25 mL volumetric flask (see 5.5). Record the specimen mass m. Dilute to the volume with acetonitrile (see 4.1). Shake thoroughly to maximize the dispersion of the specimen. Make a specimen solution. Record the constant volume V. After ultrasonic extraction for 10 min with an ultrasonic extraction instrument (see 5.3), use a graduated pipette (see 5.6) to transfer about 7 mL of the above solution into a centrifuge tube (the volume of the solution for centrifugation can also be adjusted according to actual conditions). Centrifuge for 20 ~ 30 min under the condition that the centrifuge cavity temperature does not exceed 40°C until clear liquid A appears in the upper layer. NOTE: If the centrifugation effect is not good and effective stratification cannot be achieved, the speed can be increased appropriately or the centrifugation time can be increased appropriately.

7 Test steps