Abstract

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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