Overview
ISO 15373:2001 - Plastics - Polymer dispersions - Determination of free formaldehyde specifies two validated analytical methods for measuring free formaldehyde (HCHO) in polymer dispersions. The standard was evaluated on acrylic, acrylonitrile‑butadiene, carboxylated styrene‑butadiene and vinyl acetate dispersions and is applicable to other polymer dispersion types. It defines sample preparation (filtration, centrifugation, coagulation), reagents (including Nash reagent and Carrez clarifiers), calibration and reporting to ensure reproducible quantification of free formaldehyde without disturbing phase equilibria.
Key topics and technical requirements
- Two complementary methods
- Method A (spectrophotometric): Preferred for free‑formaldehyde contents higher than 10 mg/kg. Reaction with 2,4‑pentanedione (Nash reagent) and measurement of absorbance at 410 nm.
- Method B (HPLC with post‑column reaction): Recommended for lower concentrations or arbitration. Reversed‑phase C18 column, post‑column Nash derivatization, UV detection at 410 nm; highly selective for formaldehyde.
- Sample preparation: Procedures to separate polymers from aqueous phase - filtration (0.1 µm), high‑speed centrifugation, or coagulation using Carrez reagents - to avoid generating or depleting free formaldehyde.
- Reagents and standards: Preparation of Nash reagent, mobile phase (phosphate buffer or water), and formaldehyde standard reference solutions (stock and calibration series). Stock and standards are refreshed weekly; ISO 2227 referenced for formaldehyde assay.
- Instrumentation parameters (method B): Typical settings include 0.6 ml/min mobile phase flow, PCR at 95 °C, 0.5 ml/min reagent flow, 50 µl injection and column guard use - ensuring consistent HPLC performance.
- Interferences: Potential interferents (e.g., acetaldehyde, glyoxylic acid) are noted - Method B provides higher specificity because of chromatographic separation.
Applications and who uses it
- Quality control and incoming inspection for waterborne paints, coatings, adhesives, textile finishes and latex products to monitor free formaldehyde levels.
- Regulatory and safety testing where free formaldehyde limits apply (consumer products, occupational exposure considerations).
- R&D and formulation development for polymer chemists developing acrylics, SBR, PVAc and other dispersions.
- Analytical laboratories performing validated HPLC or spectrophotometric assays and arbitration testing.
Practical benefits include minimized artefactual changes in HCHO during analysis and defined calibration/reporting procedures for reproducible results.
Related standards
- ISO 2227 - Determination of formaldehyde content in industrial formaldehyde solutions (used for standard preparation).
- ISO 3696 - Water for analytical laboratory use (specifies grade 1 water).