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Determination of the Best Digestion and Extraction Methods for the Quantification of Microplastics in Landfill Leachate

Microplastics 2026
Francisco Alvirde-Díaz, Fredy Cuellar-Robles, Javier Illescas, Alethia Vázquez‐Morillas, María del Carmen Carreño de León, María del Consuelo Hernández-Berriel

Summary

Landfills leak liquid waste (called leachate) that can carry microplastics into soil and groundwater, but measuring these tiny plastic bits accurately has been tricky because the chemicals used to clean samples can accidentally destroy the plastics being tested. This study found a specific combination of cleaning chemicals (a peroxide-based solution plus a zinc chloride salt solution) that recovers over 96% of microplastics without damaging them, giving scientists a more reliable method to track plastic pollution from landfills. Better detection methods matter because they help researchers understand how much microplastic contamination is actually escaping into the

Microplastics (MP) in landfill leachate represent an analytical challenge due to matrix complexity and the need for methods that remove interferents without degrading polymers. This study evaluated the efficiency of four digestion methods (30% H2O2, Fenton, 10% NaOH, and 20% HCl) and three density separation solutions (CaCl2, NaI, and ZnCl2) for MP quantification in leachate from the Zinacantepec Sanitary Landfill, Mexico. Samples were spiked with seven polymer types (polyethylene terephthalate (PET), high-density polyethylene (HDPE), polyvinyl chloride (PVC), low-density polyethylene (LDPE), polypropylene (PP), polystyrene (PS), and polyamide (PA)). Results analyzed by ANOVA (p < 0.05) showed that Fenton reagent was the most efficient digestion method, achieving 99% MP recovery, whereas alkaline and acid digestions caused degradation of PET, PS, and PA. Regarding density separation, ZnCl2 (1.7 g/cm3) achieved recovery exceeding 99% for all polymers. The proposed protocol enables effective isolation and identification of degraded microplastics, contributing to advance the understanding of degradation processes and transformation pathways of MP in complex environmental matrices. The combination of Fenton digestion and ZnCl2 separation showed the highest overall performance, with an efficiency greater than 96%, supporting its use as a reliable protocol for MP quantification in leachate and contributing to methodological standardization in this field.

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