From Collection to Analysis: A Practical Guide to Sample Preparation and Processing of Microplastics

Importance of the Topic

Microplastics are ubiquitous environmental contaminants with sizes between 1 and 5000 um and represent a growing concern for ecosystems and human health Standardized and robust analytical workflows are essential to produce reliable data and ensure comparability across studies

Objectives and Study Overview

This technical guide outlines a practical workflow for microplastics sample preparation from collection to analysis It focuses on establishing laboratory best practices and describing sample digestion density separation filtration and characterization using the Agilent 8700 LDIR chemical imaging system

Methodology and Instrumentation

Sample digestion employs hydrogen peroxide Fentons reagent and acids or enzymes to remove organic matrices while preserving polymer integrity Density separation utilizes salts such as NaCl CaCl2 NaI and ZnCl2 to concentrate microplastics by exploiting polymer densities Filtration captures isolated particles on gold or aluminum coated filters for direct on filter LDIR analysis List of used instrumentation

• Agilent 8700 Laser Direct Infrared chemical imaging system
• Agilent Cary 630 FTIR spectrometer
• Vacuum filtration apparatus with coated membrane filters
• Laminar flow hood and HEPA filtered air purifier
• Ultrapure water system vacuum pump balance and hot plate

Main Results and Discussion

The workflow was applied to various matrices

• Bottled drinking water direct filtration enabled rapid particle enumeration and polymer identification
• Environmental water required H2O2 digestion and CaCl2 density separation before LDIR analysis
• Soil and sediment samples were dried sieved enzymatically digested and separated by salt flotation
• Infant formula digestion with nitric acid and ethanol treatment allowed effective microplastics recovery

Benefits and Practical Applications

The optimized protocol streamlines microplastics isolation reduces contamination risk and enables high throughput analysis using LDIR This approach yields reproducible results supports QAQC practices and can be adapted for environmental monitoring and food safety testing

Future Trends and Opportunities

Emerging directions include development of standardized reference materials automation of sample processing integration of machine learning for spectral classification and novel reagents for challenging matrices Continued innovation will enhance sensitivity throughput and harmonization across laboratories

Conclusion

A comprehensive and standardized sample preparation workflow combined with LDIR imaging delivers accurate reliable and efficient microplastics characterization across multiple matrices Adoption of these best practices will advance understanding of microplastic distribution impacts and mitigation strategies

Reference

Key sources include guidelines on sample digestion QAQC and LDIR analysis summarized to guide implementation

• Ziani et al Nutrients 2023
• Wang et al TrAC 2018
• Samandra et al Agilent Technologies application notes 2023