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Developing a systematic method for extraction of microplastics in soils

Radford, Freya; Zapata-Restrepo, Lina M.; Horton, Alice A.; Hudson, Malcolm D.; Shaw, Peter J.; Williams, Ian D.

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Freya Radford

Lina M. Zapata-Restrepo

Alice A. Horton

Malcolm D. Hudson

Peter J. Shaw

Ian D. Williams


Microplastics are an environmental issue of global concern. Although they have been found in a range of environments worldwide, their contamination in the terrestrial environment is poorly understood. The lack of standardised methods for their detection and quantification is a major obstacle for determining the risk they pose to soil environments. Here we present a systematic comparison of microplastic extraction methods from soils, taking into account the characteristics of the soil medium to determine the best methods for quantification. The efficiency of organic matter removal using hydrogen peroxide, potassium hydroxide and Fenton's reagent was measured. Soils with a range of particle size distribution and organic matter content were spiked with a variety of microplastic types. Density separation methods using sodium chloride, zinc chloride and canola oil were tested. Recovery efficiencies were calculated and the impact of the reagents on the microplastics was quantified using Attenuated Total Reflectance (ATR) Fourier Transform-Infrared (FTIR) spectroscopy. The optimal organic removal method was found to be hydrogen peroxide. The recovery efficiency of microplastics was variable across polymer types. Overall, canola oil was shown to be the optimal method for density separation, however, efficiency was dependent on the amount of organic matter in the soil. This outcome highlights the importance of including matrix-specific calibration in future studies considering a wide range of microplastic types, to avoid underestimation of microplastic contamination. We show here that methods for extracting microplastics from soils can be simple, cost-effective and widely applicable, which will enable the advancement of microplastic research in terrestrial environments.


Radford, F., Zapata-Restrepo, L. M., Horton, A. A., Hudson, M. D., Shaw, P. J., & Williams, I. D. (in press). Developing a systematic method for extraction of microplastics in soils. Analytical Methods, 13(14), 1695-1705.

Journal Article Type Article
Acceptance Date Mar 8, 2021
Online Publication Date Mar 21, 2021
Deposit Date Jan 25, 2023
Publicly Available Date Jan 25, 2023
Journal Analytical Methods
Print ISSN 1759-9660
Electronic ISSN 1759-9679
Publisher Royal Society of Chemistry
Peer Reviewed Peer Reviewed
Volume 13
Issue 14
Pages 1695-1705
Keywords General Engineering; General Chemical Engineering; Analytical Chemistry
Public URL
Publisher URL
Additional Information : This document is Similarity Check deposited; : Supplementary Information; : Freya Radford (ORCID); : Alice A. Horton (ORCID); : Ian D. Williams (ORCID); : Single-blind; : Received 10 November 2020; Accepted 8 March 2021; Advance Article published 22 March 2021; Version of Record published 15 April 2021


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