GB/T 43085-2023 English PDF (GBT43085-2023)

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GB/T 43085-2023: Plastics - Polymer dispersions - Determination of the content of free formaldehyde
GB/T 43085-2023
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 83.080.01
CCS G 31
Plastics - Polymer dispersions - Determination of the content
of free formaldehyde
(ISO 15373:2001, Plastics - Polymer dispersions - Determination of free
formaldehyde, MOD)
ISSUED ON: SEPTEMBER 07, 2023
IMPLEMENTED ON: APRIL 01, 2024
Issued by: State Administration for Market Regulation;
Standardization Administration of the People's Republic of China.
Table of Contents
Foreword ... 3
1 Scope ... 5
2 Normative references ... 5
3 Terms and definitions ... 5
4 General rules ... 5
5 Reagents ... 6
6 Instruments and equipment ... 9
7 Test steps ... 11
8 Calculation and presentation of results ... 15
9 Precision ... 16
10 Test report ... 16
Annex A (informative) Comparison list of structural numbers ... 18
Annex B (informative) Precision for Method B ... 21
Bibliography ... 23
Plastics - Polymer dispersions - Determination of the content
of free formaldehyde
WARNING -- This document may involve hazardous chemicals, materials and
operations. This document does not identify all possible security issues. Users are
responsible for taking appropriate safety and health measures and ensuring
compliance with relevant national regulations.
1 Scope
This document describes a spectrophotometric method (Method A) and a high-
performance liquid chromatographic method (Method B) for the determination of free
formaldehyde (HCHO) content in polymer dispersions.
This document applies to polymer dispersions such as acrylic, acrylonitrile butadiene,
carboxylated styrene butadiene and vinyl acetate.
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 6682, Water for analytical laboratory use -- Specification and test methods
(GB/T 6682-2008, ISO 3696:1987, MOD)
ISO 2227, Formaldehyde solutions for industrial use - Determination of
formaldehyde content
3 Terms and definitions
There are no terms or definitions to be defined in this document.
4 General rules
This document contains two methods (Method A and Method B). Method A is more
suitable for polymer dispersions with free formaldehyde content above 10 mg/kg.
Method B shall be used when the free formaldehyde content is less than or equal to 10
mg/kg. Both methods minimize changes in free formaldehyde concentration caused by
changes in the physical or chemical properties of the polymer dispersion.
NOTE: When measuring free formaldehyde content in polymer dispersions, disruption of the
equilibrium between the aqueous and polymer phases can produce or consume formaldehyde. Both
methods provide steps for detecting low levels of free formaldehyde in polymer dispersions without
disturbing the existing equilibrium.
The polymer phase in the polymer dispersion is separated from the aqueous phase by
filtration, centrifugation or coagulation to obtain a sample aqueous solution. Add Nash
reagent to the sample aqueous solution. Use spectrophotometry directly (Method A).
Test the sample absorbance at 410 nm. Calculate the formaldehyde concentration to be
measured through the standard curve. Acetaldehyde and glyoxylic acid may interfere
with formaldehyde testing when using Method A. But interference will only occur when
the concentration of acetaldehyde and glyoxylic acid exceeds the concentration of
formaldehyde by 100 times.
NOTE: For dispersions with smaller particle sizes, particles that cannot be completely filtered will
interfere with the detection of the spectrophotometer, thus affecting the detection accuracy.
If high performance liquid chromatography (Method B) is used, use water as the mobile
phase. Formaldehyde and other substances can be separated by a liquid chromatograph
equipped with an octadecyldimethylsilane (C18) reversed-phase column. The
concentration of free formaldehyde in the aqueous solution was obtained by measuring
the peak areas of the standard and sample chromatographic peaks (using external
standard calibration method). Because potential interfering substances (such as
acetaldehyde, acetone, benzaldehyde, formamide, formic acid, glyoxylic acid and
propionaldehyde) can be separated from formaldehyde by chromatography or do not
react with post-column reagents, this method is specific for the determination of
formaldehyde.
The detection system for Method B consists of a post-column reactor that reacts
formaldehyde with Nash reagent to form pyridine derivatives and a UV/visible detector
that operates at 410 nm. Due to the different compositions of the polymer dispersions,
compounds remaining on the column after analysis may interfere with the
formaldehyde peak in subsequent samples. It may be necessary to extend the method
run time to elute compounds with longer retention times.
5 Reagents
Unless otherwise specified, all reagents used are analytically pure, and the experimental
water shall meet the requirements for grade one water specified in GB/T 6682.
5.1 Glacial acetic acid.
5.2 Ammonium acetate.
5.3 Formaldehyde solution.
37% formaldehyde aqueous solution.
5.4 2,4-Pentanedione (acetylacetone).
5.5 Phosphoric acid solution: Dissolve 2.3 mL of 85% phosphoric acid (H3PO4) in water.
Use water to dilute to 1 L. Prepare an aqueous solution with a concentration of 33
mmol/L.
5.6 Potassium ferrocyanide trihydrate solution (Carrez solution I): Dissolve 36 g of
potassium ferrocyanide trihydrate [K4Fe(CN)6 · 3H2O] in water. Use water to dilute to
1 L. Prepare a solution with a concentration of 36 g/L.
5.7 Zinc sulfate heptahydrate solution (Carrez solution II): Dissolve 72 g of zinc sulfate
heptahydrate (ZnSO4 · 7H2O) in water. Use water to dilute to 1 L. Prepare a solution
with a concentration of 72 g/L.
5.8 Sodium hydroxide solution: Dissolve 4 g of sodium hydroxide (NaOH) in water.
Use water to dilute to 1 L. Prepare an aqueous solution with a concentration of 0.1
mol/L.
5.9 Disodium hydrogen phosphate.
5.10 Nash reagent
Transfer 62.5 g of ammonium acetate (5.2) into a 1 L brown reagent bottle (6.1)
equipped with stirring. Add 600 mL of water. Stir to dissolve. After the ammonium
acetate is dissolved, add 7.5 mL of glacial acetic acid (5.1), 5 mL of 2,4-pentanedione
(5.4) and 387.5 mL of water to the bottle. Mix thoroughly (recommended 45 min).
NOTE: If necessary, use Nash reagent containing varying concentrations of ammonium acetate,
glacial acetic acid, and acetylacetone.
Since 2,4-pentanedione is photosensitive, Nash reagent shall be stored protected from
light.
Fresh Nash reagent needs to be prepared weekly. Degas the Nash reagent with helium
before use.
When using Method B, transfer the Nash reagent to the post-column reactor (6.6.2).
The reactor shall be protected from light.
5.11 Mobile phase and standard diluent
5.11.1 Preparation of mobile phase
Transfer 1.78 g of disodium hydrogen phosphate (5.9) to a 2 L mobile phase reservoir
equipped with stirring. Add 2 L of water and mix until disodium hydrogen phosphate is
completely dissolved.
6 Instruments and equipment
6.1 Brown bottle
The capacity is 1 L and it can filter out ultraviolet and visible light.
6.2 Sample filter
It consists of a 5 mL sample syringe and a 0.1 μm filter head, which can remove
par...