PURPOSE
Formaldehyde is extracted from a textile sample in water
at 40˚C. The amount of formaldehyde is then determined colourimetrically.
EQUIPMENT
• Distilled
water
• Ammonia
Acetate powder, analytical grade
• Glacial
Acetic Acid liquid
• Acetylacetone
liquid
• 35-40%
Formaldehyde solution
• Potassium
Hydroxide (KOH) powder
• Thymolftalene
indicator
• Saturated
Sodium Sulphite (Na2SO3) solution
• Sulphuric
Acid (H2SO4)
• Glass flasks
with stopper, 150 ml.
• Measuring
cylinder
• Funnel.
• Water bath
with temperature control.
• Volumetric
flask, 1000 ml and 100 ml.
• Balance,
accuracy 0.01 g
• Pipette
• Titration
equipment
• Test tubes
• Tube rack
• Cuvettes
•
Spectrophotometer for Formaldehyde testing according to ISO 14184-1 and JIS
1041-1983 method A
TEST
SPECIMEN
•
Each colour on the fabric and leather shall be tested separately if possible.
•
Labels shall be tested separately.
•
Each part of the garment (e.g. fusing, padding or print) should be tested
separately.
•
Iron on patches shall be tested together with the fabric after being ironed
onto the fabric.
•
Garments with print should be tested twofold; one test with only textile and
one test with fabric completely covered with print. Colours do not need to be
separated.
• Embroidery
shall be tested together with fabric. If possible separate colours.
Each test specimen is 2.50 g.
PREPARATION
OF SOLUTIONS
Preparation
of the sample solution
a)
Put exactly 2.50 g of the fabric sample from the plastic bag in a flask with
stopper. Use gloves. Cut the fabric sample into many small pieces.
b)
Note the exact weight on the report sheet.
c)
Add 100 ml distilled water to the flask.
d)
Shake the flask until the fabric is wet.
e) Put the
flask in the water bath for one hour at (40±2)°C.
Preparation
of the acetylacetone reagent solution
a)
Dissolve 150 g ammonia acetate in ~800 ml distilled water.
b)
Add 3 ml of glacial acetic acid.
c)
Add 2 ml of acetylacetone.
d)
Shake to mix thoroughly.
e) Add
distilled water so the total volume is exactly 1000 ml.
The acetylacetone reagent solution cannot be stored and
must be freshly prepared each day of testing.
Preparation
of the standard formaldehyde solution
a) Pipette 10
ml of 35%-40% formaldehyde solution to a flask.
b)
Add distilled water to 1000 ml (solution 1).
c)
Pipette 10 ml of solution 1 to a new flask.
d)
Add distilled water to 1000 ml (solution 2).
e)
Pipette 10 ml of solution 2 to a small flask.
f) Add
distilled water to 100 ml (solution 3).
The standard formaldehyde solution cannot be stored and
must be freshly prepared each day of testing.
Confirmation
of the concentration of the standard formaldehyde solution
a)
Pipette 25 ml of formaldehyde solution 1 into a vessel.
b)
Neutralise with a small amount of potassium hydroxide (KOH) solution using
thymolftalene as indicator.
c)
Add 25 ml neutral, saturated sodium sulphite (Na2SO3) solution and leave the
liquid still for one minute. The sodium sulphite solution can be neutralised
with a small amount (drops) of sulphuric acid (H2SO4).
d)
Titrate the solution with N/10 H2SO4 (N=equivalent concentration of H2SO4). The
consumption of H2SO4= V in the formula below.
e) The
concentration of the formaldehyde solution 1 can be calculated from the
formula:
Solution 1 =
(30*N*V)/25 g/l
Where N =
equivalent conc. of H2SO4 and V= consumption of H2SO4 (ml)
3.5 <
solution 1 < 4.0 g/l
3.5 < solution 3 < 4.0 μg/ml (= mg/kg)
METHOD
Preparation
of the samples for measuring with the spectrophotometer
NOTE! It is
very important to be careful, every drop will affect the result.
Sample 1. A0 5
ml sample solution from sample 1 5 ml distilled water
Sample 1, A1 5
ml sample solution from sample 1 5 ml acetylaceton reagent solution
Sample 1, A2 5 ml sample solution from sample 1 5 ml
acetylaceton reagent solutionAform: 5 ml standard formaldehyde solution
(solution 3) 5 ml acetylaceton reagent solution
Acal: 5 ml distilled
water 5 ml acetylaceton reagent solution
Place the test tubes with stopper in a tube rack and put
them in a water bath for 30 min at (40±2)°C. Let the samples cool at room
temperature for 30 min.
Measuring
with the spectrophotometer
The absorbencies
of the samples prepared are measured at wavelength 412 nm (nanometre) for both
the ISO and JIS method.
Put one sample
solution into one cuvette and measure it in the spectrophotometer. When
measuring the A0-samples, distilled water shall be used as zero samples. When
measuring A1, A2, Aform, Acal shall be used as zero sample.
If both JIS and ISO method is performed in the same day,
do not forget to re-measure A0, Acal and distilled water at the correct
wavelength.
RESULT
The result
shall be reported as follows:
For children’s
wear up to size 98cl (JIS method):
• The amount of
formaldehyde in the sample is reported in absorbance (A-A0) with 2 decimals.
For other
samples (ISO method):
• The amount of
formaldehyde in the sample is reported in ppm (mg/kg) without decimals.
• If the result
is less than 16 ppm it shall be reported as “not detectable” (n.d.).
JIS METHOD
VS. ISO METHOD
JIS method
reports the result directly with an absorbance value without calculating the
ppm. However, in order to compare also the JIS samples against a standard,
following procedure shall be followed:
• Measure
absorbance at 412 nm, mark it in the result form.
• Calculate ppm
in the fabric with the “Form-Calculation.xls” sheet.
• If A<0.05
in the UV-VIS and the corresponding ppm is maximum 15 ppm, the sample is
considered OK. If the corresponding ppm is more than 15 ppm, the sample should
be re-measured or sent to Bureau Veritas for confirmation test.
