Warning: the personnel using this Part of GB/T 2912 shall have practical experiences in regular laboratory work. This Part does not point out all the possible safety problems. Users have the responsibility to take appropriate safety and health measures and also ensure meeting the conditions specified in relevant regulations of the State.
1 Scope
This Part of GB/T 2912 specifies a method for determining the amount of free formaldehyde extracted through water extraction method and partly through hydrolysis.
This Part is applicable to the textile samples in any form.
This Part is applicable to the textiles with free formaldehyde content between 20mg/kg~3500 mg/kg. The lower limit is 20 mg/kg. Below this limit the result is reported as 'not detectable'.
2 Normative References
The following standards contain provisions which, through reference in this Part of GB/T 2912, constitute provisions of this standard. For dated reference, subsequent amendments to (excluding correction to), or revisions of, any of these publications do not apply. However, the parties to agreements based on this standard are encouraged to investigate the possibility of applying the most recent editions of the standards. For undated references, the latest edition of the normative document referred to applies.
GB/T 6529 Textiles-Standard atmospheres for conditioning and testing (GB/T 6529-2008, ISO 139:2005, MOD)
GB/T 6682 Water for analytical laboratory use - Specification and test methods (GB/T 6682-2008, ISO 3696:1987, MOD)
GB/T 11415 Laboratory sintered (fritted) filters-Porosity grading, classification and designation (GB/T 11415-1989, ISO 4793:1980, NEQ)
3 Principle
Specimen is extracted in the water bath at 40°C for a certain time. After the extraction liquid develops by the acetylacetone, the absorbance of formaldehyde in the color reagent is determined by the spectrophotometer under 412 nm wave length. The results are compared with the standard formaldehyde working curve. The content of free formaldehyde in the sample is then calculated.
4 Reagents
All reagents shall be analytical reagent quality.
4.1 Distilled water or grade 3 water
Complying with GB/T 6682
4.2 Acetylacetone reagent (Nash reagent)
Dissolve 150g of ammonium acetate in about 800mL of water, add 3mL of glacial acetic acid and 2mL of acetylacetone, transfer into a 1000mL volumetric flask and make up to the mark with water, store in a brown bottle.
Note: the reagent darkens in color slightly on standing over the first 12 h, for this reason the reagent should be held 12 h before use. The validity is 6 weeks. Since the sensitivity may change slightly over a long period of time, it is good practice to run a calibration curve weekly to correct for slight changes in the standard curve.
4.3 Formaldehyde solution
Approximately 37% (mass concentration).
4.4 Ethanolic solution of dimedone
Prepare by dissolving 1g of dimedone (dimethyl-dihydro-resorcinol or 5,5-diraethyl-cyclohexanedione) in ethanol and by diluting the solution with ethanol to make 100mL. Prepare immediately before use.
