1、BRITISH STANDARD BS 6806:2002 Textiles Determination of formaldehyde Method for the determination of total and free (water extraction method) formaldehyde using chromotropic acid ICS 59.080.01 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBS 6806:2002 This British Standard, h
2、aving been prepared under the direction of the Sector Policy and Strategy Committee, was published under the authority of the Standards Policy and Strategy Committee on 17 May 2002 BSI 17 May 2002 The following BSI references relate to the work on this British Standard Committee reference TCI/80 Dra
3、ft for comment 01/122797 DC ISBN 0 580 38851 4 Committees responsible for this British Standard The preparation of this British Standard was entrusted by Technical Committee TCI/80, Chemical testing of textiles, upon which the following bodies were represented. Association of Consulting Scientists A
4、ssociation of Suppliers to the British Clothing Industry British Apparel monitor related international and European developments and promulgate them in the UK. A list of organizations represented on this committee can be obtained on request to its Secretary. The method described in this revision of
5、BS 6806 is not compatible with BS EN ISO 14184-2 because of the different chemistry used to determine the formaldehyde. A British Standard does not purport to include all necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a B
6、ritish Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages 1 to 6, an inside back cover and a back cover. The BSI copyright notice displayed in this document indicates when the docume
7、nt was last issued.BS 6806:2002 BSI 17 May 2002 1 1 Scope This British Standard describes two methods for determining formaldehyde on textiles: “total formaldehyde” and “free and water-soluble formaldehyde” using chromotropic acid and sulfuric acid for detection and quantification. The methods may b
8、e applied to any textile product containing a formaldehyde-based precursor. The methods are not compatible with and cannot be compared directly with BS EN ISO 14184-1 and BS EN ISO 14184-2. 2 Normative references The following referenced documents are indispensable for the application of this docume
9、nt. For dated references, only the edition cited applied. For undated references, the latest edition of the referenced document (including any amendments) applies. BS 1752, Specification for laboratory sintered or fritted filters including porosity grading ISO 4793:1980. BS EN ISO 3696, Water for an
10、alytical laboratory use Specification and test methods. 3 Apparatus and reagents 3.1 Balance, accurate to 0.000 1 g. 3.2 Conical flasks, 150 ml and 100 ml, fitted with ground glass stoppers. 3.3 Boiling tubes, 150 mm 25 mm. 3.4 Sintered glass filters, of porosity P160 (see BS 1752) to fit the neck o
11、f the boiling tubes. 3.5 Water bath, capable of maintaining (25 1) C and (100 2) C. 3.6 Volumetric flasks, 50 ml. 3.7 Spectrophotometer, for measuring absorbance at a wavelength at 570 nm; bandwidth 8 nm or better. 3.8 Purified water, complying with or better than BS EN ISO 3696 Grade 3. 3.9 Chromot
12、ropic acid, (disodium-4,5-dihydroxynapthalene-2,7-disulfonic acid) 50 g/l aqueous solution, freshly prepared (no older than 12 h) and, if necessary, filtered before use. NOTE A new calibration curve should be prepared for each new bottle opened. 3.10 Concentrated sulfuric acid, (density 1.84 g/ml) o
13、f analytical reagent quality. 3.11 Sulfuric acid, 6 M. This is prepared by carefully adding concentrated sulfuric acid (600 g, 325 ml, 3.10) to purified water (3.8) and making up to one litre when cooled to 18 C to 22 C. 3.12 Sulfuric acid, 7.5 M. This is prepared by carefully adding concentrated su
14、lfuric acid (750 g, 405 ml, 3.10) to purified water (3.8) and making up to one litre when cooled to 18 C to 22 C. WARNING These two methods use concentrated acids. Standard safety precautions for handling concentrated acids should be used. 3.13 Formaldehyde solution in water, nominally 370 g/l of ge
15、neral purpose reagent quality. 3.14 Wetting agent, comprising of a 1 g/l in purified water (3.8) solution of nonionic ethoxylated alkyl phenol. NOTE 1 The choice of wetting agent as received is governed by its effectiveness in wetting out the specimen without affecting the subsequent colorimetric an
16、alysis. Certain wetting agents and concentrations higher than 1g /l hinder the development of the coloured complex. NOTE 2 A new calibration curve should be made for each new batch of wetting agent.BS 6806:2002 2 BSI 17 May 2002 4 Total formaldehyde 4.1 Principle A sample of known mass of a textile
17、material is immersed for four hours in a measured volume of aqueous sulfuric acid. After filtration, an aliquot of the filtrate is treated with chromotropic acid and concentrated sulfuric acid and heated in a water bath for 30 min to produce a deep red-violet colour. The solution is then cooled and,
18、 after it has been diluted to a fixed volume, its absorbance is measured. The amount of formaldehyde corresponding to the measured absorbance is obtained from a calibration curve prepared under identical conditions. 4.2 Test specimens 4.2.1 Samples from which test specimens are taken shall be indivi
19、dually enclosed in sealed polythene bags until required for analysis. 4.2.2 From a sample, take a diagonal strip and cut it into squares approximately 8 mm 8 mm. Mix them thoroughly and accurately weigh two duplicate specimens of (1.00 0.02) g. NOTE Possible variation in moisture content within the
20、sample is not thought to be significant. Exposure to the air for conditioning in a standard atmosphere or drying will significantly affect the result. The result can be affected by the time delay between resin fixation (curing) and carrying out the test. 4.3 Procedure 4.3.1 Carry out the following p
21、rocedure on each of the duplicate specimens prepared as described in 4.2. 4.3.2 Transfer the test specimen to a 150 ml stoppered conical flask (3.2). Add 100 ml of 6 M sulfuric acid (3.11), shake the flask gently and set it aside for a minimum of four hours to a maximum of 20 h to ensure complete hy
22、drolysis of the formaldehyde-based finish. Filter a 5.0 ml to 10 ml portion of the liquid through the glass sinter (3.4) to remove any loose fibres. NOTE The textile to acid ratio is 1:100. Corresponding smaller quantities of reagent can be employed, with a recommended minimum specimen size of 0.2 g
23、 contained in a 50 ml stoppered conical flask. 4.3.3 Transfer an aliquot of 0.5 ml or 1 ml of the filtrate to a boiling tube (3.3). Up to 5 ml may be used for solutions with low concentrations of formaldehyde. Add 6 M sulfuric acid (3.11) to the aliquot such that the total volume is 5 ml then add 1.
24、0 ml of chromotropic acid solution (3.9) and 5.0 ml of concentrated sulfuric acid (3.10). Mix the contents of the tube after each addition, with a two to three minute wait before adding the next reagent. 4.3.4 Support the tube vertically in the boiling water bath for (30 1) min. NOTE The level of th
25、e water should be above the level of the reagents in the tube to ensure adequate heating. Remove it from the water bath and allow to cool. When cool, transfer the solution to a 50 ml volumetric flask (3.6), rinsing the contents into the flask, and make up to 50 ml with purified water (3.8). The temp
26、erature of the flask contents will rise during this procedure. Allow the contents to cool for one hour and make up to 50 ml if necessary. 4.3.5 Using the spectrophotometer, measure the absorbance at 570 nm of the solution prepared in 4.3.4 in a 10 mm cell against a blank solution made from 5.0 ml of
27、 6 M sulfuric acid (3.11), 1.0 ml of chromotropic acid solution (3.9) and 5.0 ml of concentrated sulfuric acid (3.10). 4.3.6 If the absorbance exceeds 1.0 or is less than 0.1, repeat the colorimetric determination 4.3.3, 4.3.4 and 4.3.5 using a smaller or larger aliquot of filtrate. NOTE 1 At high f
28、ormaldehyde concentrations, the relationship between absorbance and concentration is non-linear and other coloured species are present. Therefore, at a measured absorbance of greater than 1, the procedure should be repeated using a smaller aliquot of the original acidic hydrolyzate. NOTE 2 No change
29、s in absorbance values have been observed after periods of up to four hours after colour development. NOTE 3 During dilution of the coloured solution, the contents of the volumetric flask should be mixed thoroughly to prevent to formation of layers and erroneous results.BS 6806:2002 BSI 17 May 2002
30、3 5 Free and water-soluble formaldehyde 5.1 Principle A sample of known mass of a textile material is immersed for 20 min in a measured volume of purified water containing a wetting agent. After filtration, an aliquot of the filtrate is treated with chromotropic acid and concentrated sulfuric acid a
31、nd heated in a water bath for 30 min to produce a deep red-violet colour. The solution is then cooled and, after it has been diluted to a fixed volume, its absorbance is measured. The amount of formaldehyde corresponding to the measured absorbance is obtained from a calibration curve prepared under
32、identical conditions. 5.2 Test specimens 5.2.1 Samples from which test specimens are taken shall be individually enclosed in sealed polythene bags until required for analysis. 5.2.2 From a sample, take a diagonal strip and cut it into squares approximately 8 mm 8 mm. Mix them thoroughly and weigh du
33、plicate specimens of (2.00 0.02) g. NOTE Possible variation in moisture content within the sample is not thought to be significant. Exposure to the air for conditioning in a standard atmosphere or drying will significantly affect the result. The result can be affected by the time delay between resin
34、 fixation (curing) and carrying out the test. 5.3 Procedure 5.3.1 Carry out the following procedure on each of the duplicate specimens prepared as described in 5.2. 5.3.2 Transfer the test specimen to a 100 ml stoppered conical flask (3.2). Add 20 ml of the wetting agent solution (3.14) and shake th
35、e flask gently to ensure thorough wetting out. Place the conical flask in a thermostatically controlled water bath at (25 1) C for (20 1) min, shaking intermittently. Filter a 5.0 to 10 ml portion of the liquid through the glass sinter (3.4) to remove any loose fibres. NOTE It is important to mainta
36、in the textile to wetting agent ratio at 1:10. Any change will affect the formaldehyde concentration in the final extract. 5.3.3 Transfer an aliquot of 0.5 ml or 1 ml of the filtrate to a boiling tube (3.3). Up to 5 ml may be used for solutions with low concentrations of formaldehyde. To the aliquot
37、, add 4 ml of 7.5 M sulfuric acid (3.12) then add 1.0 ml of chromotropic acid solution (3.9) and 5.0 ml of concentrated sulfuric acid (3.10). Mix the contents of the tube after each addition with a two to three minute wait before adding the next reagent. 5.3.4 Support the tube vertically in the boil
38、ing water bath for (30 1) min. NOTE The level of the water should be above the level of the reagents in the tube to ensure adequate heating. Remove from the water bath and allow to cool. When cool, transfer the solution to a 50 ml volumetric flask (3.6), rinsing the contents into the flask and make
39、up to 50 ml with purified water (3.8). The temperature of the flask contents will rise during this procedure. Allow the contents to cool for one hour and make up to 50 ml if necessary. 5.3.5 Using the spectrophotometer, measure the absorbance at 570 nm of the solution prepared in 5.3.4 in a 10 mm ce
40、ll against a blank solution made from 1 ml of wetting agent (3.14), 4.0 ml of 7.5 M sulfuric acid (3.12), 1.0 ml of chromotropic acid solution (3.9) and 5.0 ml of concentrated sulfuric acid (3.10). 5.3.6 If the absorbance exceeds 1.0 or is less than 0.1, repeat the colorimetric determination 5.3.3,
41、5.3.4 and 5.3.5 using a smaller or larger aliquot. NOTE 1 At high formaldehyde concentrations, the relationship between absorbance and concentration is non-linear and other coloured species are present. Therefore, at a measured absorbance of greater than 1, the procedure should be repeated using a s
42、maller aliquot of the original acidic hydrolyzate. NOTE 2 No changes in absorbance values have been observed after periods of up to four hours after colour development. NOTE 3 During dilution of the coloured solution, the contents of the volumetric flask should be mixed thoroughly to prevent to form
43、ation of layers and erroneous results. NOTE 4 The presence of excess nitrate or nitrite ions associated with nitrate resin catalysts affects the determination, giving low results. If the nitrate or nitrite ions are present, the coloured complex will be brown. These ions may be removed with a suitabl
44、e ion exchange resin prior to analysis. The resin (0.5 g) is added to 10 ml of the filtrate, shaken for 5 min, and the supernatant liquid is used for the analysis.BS 6806:2002 4 BSI 17 May 2002 6 Calibration graph 6.1 Prepare a stock solution containing approximately 5 mg/ml of formaldehyde by dilut
45、ing 370 g/l formaldehyde solution (13.5 ml, 3.13) with purified water (1 l, 3.8). Determine the concentration by the method described in Annex A and adjust if necessary. NOTE The stock solution will keep for about 12 months if refrigerated. Before use, the temperature of the solution should be raise
46、d to room temperature. 6.2 For the total formaldehyde method, dilute aliquots (2, 3, 4, 6, 8, 10, 12, 16, 20 ml) of the stock solution (see 5.1) in purified water grade 3 water in 500 ml volumetric flasks to give standard formaldehyde solutions containing approximately 20, 30, 40, 60, 80, 100, 120,
47、160, and 200 g/ml formaldehyde, respectively. NOTE These diluted solutions should be used immediately and should not be stored for future use. 6.3 For free and water-soluble formaldehyde method, dilute aliquots (2, 3, 4, 6, 8, 10, 12, 16, 20 ml) of the stock solution (see 6.1) in the wetting agent (
48、3.14) in 500 ml volumetric flasks to give standard formaldehyde solutions containing approximately 20, 30, 40, 60, 80, 100, 120, 160, and 200 g/ml formaldehyde, respectively. NOTE These diluted solutions should be used immediately and should not be stored for future use. 6.4 To duplicate 1.0 ml aliq
49、uots of the stock solutions, add 4.0 ml 7.5 M sulfuric acid (3.12) such that the total volume is 5 ml, then add 1.0 ml of chromotropic acid solution (3.9) and 5.0 ml of concentrated sulfuric acid (3.10). Mix the contents of the tube after each addition with a two to three minute wait before adding the next reagent. Following the procedure in 4.3.4 and 4.3.5 and 5.4.4 and 5.4.5, develop the coloured complex and measure the absorbance of the solutions. Prepare a calibration curve in which micrograms of formaldehyde p
