Accurate Microplastic Analysis of Bottled Drinking Water

Importance of the Topic

Microplastics are pervasive environmental contaminants defined as plastic particles between 1 µm and 5 mm in size. Their presence in bottled drinking water raises concerns for human exposure due to rising consumption patterns worldwide. Understanding their occurrence and sources is critical for public health and regulatory standards.

Objectives and Study Overview

This application note evaluates the performance of the Agilent 8700 Laser Direct Infrared Chemical Imaging System combined with the Agilent Cary 630 FTIR spectrometer for the accurate detection, identification and quantification of microplastics in two commercial bottled water brands. The study aims to characterize microplastic particulate load and to trace contamination sources using polymer-specific spectral libraries.

Methodology and Instrumentation

Sample volumes of 600 mL from two bottled water brands were filtered through gold-coated polyester (PETG) membrane filters using a glass frit vacuum assembly to collect particles down to 0.8 µm. Filters were analyzed directly by the Agilent 8700 LDIR system under Agilent Clarity software employing an automated particle analysis workflow with a dedicated microplastics spectral library. Key instrumental parameters such as scan speed, sweep speed and hit quality thresholds were set to default or automatic modes for rapid detection of particles across a 16 mm diameter area. To identify polymer sources, fragments of bottle and cap materials were analyzed on a diamond attenuated total reflectance (ATR) module using the Agilent Cary 630 FTIR spectrometer and a user-generated polymer library covering common plastics.

Main Results and Discussion

Brand A yielded 98 detected particles with four confirmed microplastics above the hit quality threshold of 0.80. These comprised three polyethylene and one polyethylene terephthalate fragments sized 20 to 100 µm. Brand B produced 1 112 particles with 33 microplastics identified, including 23 polyethylene, three PET and eight polyamide particles ranging up to 703 µm. Non-microplastic particles such as polyamides and cellulose were also recognized. ATR FTIR analysis confirmed that bottles for both brands were made of PET and caps of high-density polyethylene, supporting the hypothesis that opening and closing may introduce microplastic shedding.

Benefits and Practical Applications

The on-filter LDIR workflow minimizes sample handling and potential contamination while providing high throughput and reliable quantitative data. The combined approach enables laboratories to implement routine screening of drinking water and other matrices for microplastic pollution as part of quality assurance and environmental monitoring programs.

Future Trends and Potential Uses

Extended applications may include analysis of food, beverages and environmental samples beyond bottled water. Further development of polymer libraries and faster sample preparation techniques will enhance detection limits and throughput. Integration with automation platforms and data-driven mapping of microplastic distribution can support risk assessment and regulatory compliance.

Conclusion

The study demonstrates that the Agilent 8700 LDIR Chemical Imaging System paired with Agilent Clarity software and the Cary 630 FTIR spectrometer provides an accurate, efficient and robust solution for microplastic analysis in bottled drinking water. The methodology achieves confident polymer identification, high sample throughput and reduced operator risk.

References

1. GESAMP Joint Group of Experts on the Scientific Aspects of Marine Environmental Protection Sources Fate and Effects of Microplastics in the Marine Environment A Global Assessment International Maritime Organization 2015
2. Adaptation of Definition of Microplastics in Drinking Water SCCWRP 2021 2020 0021
3. Aslani H et al Tendencies Towards Bottled Drinking Water Consumption Challenges Ahead of Polyethylene Terephthalate Waste Management Health Promotion Perspectives 2021 11(1) 60–68
4. Horton AA et al Microplastics in Freshwater and Terrestrial Environments Sci Total Environ 2017 586 127–141
5. Mason SA Welch VG Neratko J Synthetic Polymer Contamination in Bottled Water Front Chem 2018 6 407
6. Primpke S et al Reference Database Design for the Automated Analysis of Microplastic Samples Based on Fourier Transform Infrared Spectroscopy Anal Bioanal Chem 2018 410 5131–5141
7. De Frond H Rubinovitz R Rochman CM μATR FTIR Spectral Libraries of Plastic Particles FLOPP and FLOPP-e for the Analysis of Microplastics Anal Chem 2021 93(48) 15878–15885
8. Samandra S et al Assessing Exposure of the Australian Population to Microplastics Through Bottled Water Consumption Sci Total Environ 2022 837 155329