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Updated: Sep 4, 2025
Separation and Identification of Conventional Microplastics from Farmland Soils
Published on: March 21, 2025
Identification and quantification of common microplastics in table salts by a multi-technique-based analytical method
Haiyan Li1, Qiong Wu1, Joee Ng1
1National Centre for Food Science, Singapore Food Agency, 10 Perahu Road, Singapore, 718837, Singapore.
Abstract:
Microplastics (MPs) are considered as contaminants of emerging concern to the environment and our food chains in recent years. In this study, we presented a multi-technique-based analytical method for detection of MPs through a combination of microscope-FTIR (μ-FTIR) with pyrolysis-GC/MS (Py-GC/MS) to achieve 3-dimensional (3D) information for the identification of polymer type, characterization of particle size and morphology, and quantification of MPs based on both particle number and mass of plastics. Plastics that are commonly used and disposed of, including polyethylene (PE), polypropylene (PP), polystyrene (PS), polyethylene terephthalate (PET), poly vinyl chloride (PVC), polyamide (PA), and poly(methyl methacrylate) (PMMA), were covered in this study. Sample extraction and separation procedures were optimized for these microplastics in table salts where good recoveries (> 75%) were achieved. To further enhance the detection sensitivity in simultaneous quantification of multiple polymers in a sample, a serial dissolution approach with different solvents was developed for the detection of all 7 types of plastics. The established sample preparation process and multi-technique-based analytical method were validated with polymer standards in table salts, resulting in satisfactory qualification and quantification for all samples tested. A retail survey of MPs in table salts was conducted with the developed analytical method, revealing that MPs were present in all commercially available table salts. The total number of MP particles varied from 20 to 125 particles/kg and the total mass contents of seven types of plastics ranged from 30 to 530 µg/kg in table salts.
Insights
Microplastics were found in all tested table salts, highlighting a significant contamination issue. This study developed a robust method to detect and quantify these plastic particles in food products.
Area of Science:
- Environmental Science
- Analytical Chemistry
- Food Safety
Background:
- Microplastics (MPs) are emerging environmental contaminants with potential impacts on food chains.
- The presence and quantification of MPs in food matrices like table salt require sensitive and accurate analytical methods.
Purpose of the Study:
- To develop and validate a multi-technique analytical method for the detection, characterization, and quantification of seven common plastic types in table salt.
- To assess the prevalence and levels of MPs in commercially available table salts.
Main Methods:
- Combined microscopy-Fourier Transform Infrared spectroscopy (μ-FTIR) with pyrolysis-Gas Chromatography/Mass Spectrometry (Py-GC/MS) for 3D MP analysis.
- Optimized sample extraction, serial dissolution, and separation procedures for high recovery rates (>75%).
- Validated the analytical method using polymer standards in table salt matrices.
Main Results:
- The developed method successfully identified and quantified seven common plastic types (PE, PP, PS, PET, PVC, PA, PMMA).
- Microplastics were detected in all samples of commercially available table salts analyzed.
- MP particle numbers ranged from 20 to 125 particles/kg, and mass content ranged from 30 to 530 µg/kg.
Conclusions:
- The study established a reliable multi-technique method for MP analysis in table salt.
- Widespread contamination of table salt with microplastics was confirmed, indicating a potential route of human exposure.
- Further research is needed to understand the toxicological implications of MPs in food.
