Development and Application of a Mass Spectrometry Method for Quantifying Nylon Microplastics in Environment

Area of Science:

• Environmental Science
• Analytical Chemistry
• Polymer Science

Background:

• Quantitative detection methods for microplastic (MP) polymers, especially nylon (polyamide, PA), in environmental matrices are insufficient.
• Existing methods lack the sensitivity and specificity required for accurate nylon MP quantification in diverse samples.

Purpose of the Study:

• To develop and validate a novel method for the quantitative detection of nylon (polyamide, PA) microplastics (MPs) in various environmental samples.
• To assess the prevalence and concentration of nylon MPs in different environmental compartments and evaluate potential human exposure pathways.

Main Methods:

• A method combining acid depolymerization with liquid chromatography-tandem mass spectrometry (LC-MS/MS) was developed for direct quantification of nylon MPs without prior separation.
• Nylon 6 (PA6) and Nylon 66 (PA66) were depolymerized into their respective monomers (6-aminocaproic acid and adipic acid) for sensitive detection.
• The method was validated using spiked environmental samples, including indoor dust, sludge, sediments, and fish tissues.

Main Results:

• The developed LC-MS/MS method achieved high recovery rates (90.8–98.8%) for spiked PA6 and PA66 MPs.
• Quantification limits for PA6 and PA66 MPs were determined as 0.680 and 4.62 mg/kg, respectively.
• Nylon MPs were ubiquitously detected across all tested environmental samples (indoor dust, sludge, marine/freshwater/fishery sediments, fish guts/gills) at concentrations ranging from 0.725 to 321 mg/kg.

Conclusions:

• The proposed acid depolymerization-LC-MS/MS method provides a reliable and efficient means for quantifying nylon MPs in complex environmental samples.
• Extremely high concentrations of PA66 MPs found in indoor dust and fish tissues indicate significant potential for human exposure via ingestion and diet.
• Further research is warranted to fully understand the environmental fate and toxicological impacts of nylon MPs.