Determination of Volatile Organic Compounds in Water-based Paints and Varnishes Using Gas Chromatography

Significance of the Topic

Water-based paints and varnishes are increasingly replacing solvent-based formulations to reduce the emission of harmful volatile organic compounds (VOCs) in indoor environments. Ensuring that these products meet regulatory VOC limits is critical for consumer safety, environmental protection and quality control in paint manufacturing.

Objectives and Study Overview

• Develop a rapid and efficient gas chromatography method for quantifying VOCs in water-based paints and varnishes.
• Analyze thirty commonly used solvents according to China’s GB 18582-2008 standard.
• Validate the method’s precision, repeatability and regulatory compliance.

Methodology

Paint samples were spiked with two internal standards (dimethyl glycol and dimethyl diglycol) and a boiling point marker (diethyl adipate), diluted in acetonitrile, sonicated, centrifuged and filtered. One-point calibration curves were generated for each sample based on known concentrations, while unknown peaks eluting before the boiling point marker were quantified using an assumed response factor.

Used Instrumentation

• Gas chromatograph: Shimadzu GC-2025 equipped with an AOC-20i auto-injector.
• Column: J&W DB-1701, 30 m×0.25 mm×0.25 µm film thickness.
• Detector: FID-2010 operated at 280 °C with hydrogen (30 mL/min), air (400 mL/min) and nitrogen makeup gas (40 mL/min).
• Carrier gas: High-purity helium in constant linear velocity mode (37.5 cm/s).
• Oven temperature program: 35 °C (1 min) to 60 °C at 20 °C/min, to 90 °C at 30 °C/min, to 150 °C at 35 °C/min, and to 240 °C at 20 °C/min (total run time 10.5 min).

Main Results and Discussion

The optimized method achieved baseline separation of 35 peaks (30 VOCs, two internal standards and a boiling point marker) within 10.5 minutes. Repeatability tests yielded relative standard deviations below 0.5% at 300 mg/L and below 2% at 30 mg/L. Total xylenes were measured as a sum of all isomers without requiring full chromatographic resolution of m- and p-xylene. Two commercial water-based paint samples were analyzed, yielding total VOC contents of 32.8 g/L (indoor paint) and 50.2 g/L (outdoor paint), both well below the 120 g/L regulatory limit. Unknown peaks eluting before the boiling point marker were quantified using an internal standard assumption, resulting in values consistent with expected solvent usage. Repeatability within a single operator and laboratory showed absolute differences below 0.009%.

Benefits and Practical Applications

Ultrafast analysis enables high sample throughput in QC laboratories. The one-point internal standard calibration simplifies workflow and minimizes solvent consumption. Compliance with international and national regulations is assured, supporting paint formulators and regulatory bodies in routine monitoring.

Future Trends and Possibilities

• Integration with mass spectrometry for identification of unknown impurities.
• Automation and online sampling for real-time VOC monitoring during production.
• Extension to ultra-low-VOC formulations and emerging green solvents.
• Data-driven optimization of temperature programs for further run time reduction.

Conclusion

A robust, rapid GC-FID method was established for quantifying thirty VOCs in water-based paints and varnishes. The approach delivers excellent precision and regulatory compliance within a 10.5-minute cycle, supporting efficient quality control and environmental safety.

References

1. G. Wieslander, D. Norbäck, E. Björnsson. Int. Arch. Occup. Environ. Health 1997, 69, 115–124.
2. U.S. EPA. Introduction to Indoor Air Quality. Accessed June 2014.
3. Comparison of Water-Based vs. Solvent-Based Paints. PaintQuality.com. Accessed June 2014.
4. GB 18582-2008. Indoor Decorating and Refurnishing Materials – Limit of Harmful Substances.
5. ISO 11890-2:2013. Paints and Varnishes – Determination of VOC Content by Gas Chromatography.