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Methods of analysis and control of residual monomer in polymers

July 14, 2025
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Introduction

Monitoring residual monomers in polymer products is an essential aspect of quality control in the polymer, food, pharmaceutical and water treatment industries. The presence of free monomers may adversely affect human health and the environment. This article provides a comprehensive review of the methods of analysis and monitoring of residual monomers, focusing on acrylamide in polyacrylamide.

Part I: The Importance of Monitoring Residual Monomers

1.1 Risks of free monomers

  • Acrylamide toxicity: cancer pathogenesis (ICARC Group 2A), neurotoxicity

  • Legal  restrictions: EPA and WHO and EU regulations

  • Effects on product  quality: stability, performance and safety

1.2 Measurement challenges

  • Very   low concentrations (ppm to ppb)

  • Polymer matrix overlap

  • Allergy to sampling and preparation conditions

Part II: Chromatographic methods

2.1 High Performance Liquid Chromatography (HPLC)

  • Ideal conditions for acrylamide  :

    • Fixed phase: C18

    • Moving phase: Water/acetonitrile (10:90)

    • Detector: UV at 210 nm

  • Features  : High precision, excellent repeatability.

  • Limitations  : The need for sample preparation.

2.2 Gas chromatography-mass spectroscopy (GC-MS)

  • The standard method of volatile monomers

  • Conditions of analysis  :

    • Column: DB-5MS (30m × 0.25mm × 0.25μm)

    • Temperature Program: 50°C (two minutes) to 280°C at 10°C/min

  • Detection  limit: up to 0.01 ppm

2.3 Ion chromatography (IC)

  • Suitable for polar monomers.

  • Ideal  : conditions

    • Column: IonPac AS11-HC

    • Detergent solution: potassium hydroxide gradient

  • Application  : Ionic monomer monitoring

Part III: Spectral Methods

3.1 Fourier infrared transformation spectroscopy (FTIR)

  • identify single functional groups

  • Quantitative method using internal parameters

  • Limitation  : Relatively low sensitivity (~100 ppm)

3.2 Raman spectroscopy

  • Feature  : No need to prepare sample.

  • Application  : Online monitoring on the production line.

  • Developing SERS   methods to increase sensitivity

3.3 Nuclear magnetic resonance spectroscopy

  • 1H NMR for qualitative and quantitative analysis

  • Feature  : No need to separate

  • Limitations  : High cost and moderate sensitivity.

Part IV: Electrochemical Methods

4.1 Periodic voltmeter

  • Operating  principles: oxidation/reduction of monomer at electrode.

  • Sensitivity  : up to 0.1 ppm for acrylamide

  • Advantage  : simplicity and low cost.

4.2 Biosensors

  • Enzymes used  : hydrolysates, oxidases.

  • Sensor  platforms: modified electrodes, nanosensors

  • Feature  : High selectivity

4.3 Immune systems

  • ELISA Acrylamide Groups

  • Feature  : Suitable for field testing.

  • Boundary  : Interference with similar vehicles

Part V: New and hybrid methods

5.1 Nanotechnology-based methods

  • Nano-fluorescent sensors

  • Nanopore Platforms

  • Pre-concentration absorbent nanomaterials

5.2 Microfluidic systems

  • Microchip analyzers

  • Feature  : Reduce sample size and reagents

  • Application  : Real-time surveillance

5.3 Advanced mass spectroscopy methods

  • LC-MS/MS with extreme sensitivity

  • MALDI-TOF for complex samples

  • ICP-MS for Mineral Monomers

Part VI: Sample preparation

6.1 Polymer matrix extraction

  • Liquid-liquid extraction methods

  • Solid Phase Extraction (SPE)

  • Supercritical Fluid Extraction (SFE)

6.2 Non-extraction methods

  • Direct Thermal Analysis (PY-GC/MS)

  • Solid Phase Microextraction (SPME)

  • Membranous dialysis

6.3 Quality control in preparation

  • National Standards

  • Recovery and redundancy

  • Matrix correction

Section 7: Rules and Guidelines

7.1 International standards

  • ISO 12080: Methods for Determination of Monomers in Polymers

  • EPA 8316: Analysis of acrylamide by HPLC

  • EU 10/2011: Restrictions on monomers in food contact materials

7.2 Industrial protocols

  • Quality control methods in the polymer industry

  • Food  and pharmaceutical industry  standards

  • Water Treatment Industry Guidelines

7.3 Method certificates

  • Validation of analytical methods

  • Laboratory Quality Control (ISO 17025) 

  • Quality Assurance Systems

Part VIII: Choosing the Right Way

8.1 Criterias of choice

  • Required sensitivity

  • Sample matrix

  • Cost and analysis time

  • Available equipment

8.2 Method selection guide for acrylamide

Monomer concentration Recommended method Detection limit
>100 ppm Fourier infrared conversion 50 ppm
1-100ppm HPLC-UV 0.5 ppm
0.1-1 ppm Gas Chromatography-Mass Spectrometry 0.01 ppm
<0.1 ppm LC-MS/MS 0.001 ppm

8.3 Combination strategies

  • Quick detection in simple ways

  • Verification using more accurate methods

  • Use of complementary methods

Conclusion

The monitoring of residual monomers in polymer products, especially polyacrylamide acrylamide,  requires a systematic, multi-level approach. Thanks to recent advances in analytical techniques, methods for measuring very low monomer concentrations are now available. The choice of the right method depends on several factors, such as the sensitivity required, the type of matrix, and laboratory facilities. The development of fast, portable and low-cost methods is an active area of research in this area, which improves quality control in  industry. The application of continuous and integrated monitoring systems is essential to ensure the safety and quality of polymer products in sensitive applications.