An In Situ Depolymerization and Liquid Chromatography-Tandem Mass Spectrometry Method for Quantifying Polylactic Acid...

Area of Science:

• Environmental Science
• Analytical Chemistry
• Polymer Science

Background:

• Polylactic acid (PLA) is a widely used biodegradable plastic with increasing environmental prevalence.
• The growing use of PLA results in a predictable rise in PLA microplastic (MP) pollution.
• Current methods for quantifying PLA MPs in environmental matrices are insufficient.

Purpose of the Study:

• To develop and validate a novel analytical method for the accurate quantification of PLA MPs.
• To assess the presence and distribution of PLA MPs in environmental samples.
• To investigate PLA MP release from consumer products.

Main Methods:

• Development of an alkali-assisted thermal depolymerization technique.
• Quantification of depolymerized lactic acid using liquid chromatography-tandem mass spectrometry (LC-MS/MS).
• Direct analysis of environmental samples without prior separation or extraction.

Main Results:

• The developed method achieved a limit of quantification of 18.7 ng/g with a 93% recovery rate for spiked PLA MPs.
• PLA MPs were detected in all tested reservoir sediment samples, with concentrations ranging from 53.5-491 ng/g dw.
• Concentrations of PLA MPs in sediment decreased with increasing depth.
• Approximately 12 μg of PLA MPs were released from a single teabag after soaking in hot water.

Conclusions:

• The novel LC-MS/MS method provides a sensitive and efficient means for quantifying PLA MPs in environmental samples.
• PLA MPs are present in reservoir sediments, indicating environmental contamination.
• Consumer products like teabags can be a source of PLA MP release into the environment.