Follow up to question 3.3: Can you provide a paper that has confirmed removal of all interfering biological matrix components?

Unfortunately not.

I am not familiar with any paper in which there has been a thorough removal of all interfering biological matrix components WITHOUT a partial degradation of the polymer particles themselves. 

Methods are available and also continue to evolve to minimize or eliminate interferences in MNP analysis.  Biological samples require exhaustive extraction and purification steps.  Currently available methodologies do not have adequate purification steps.  For example, one study showed that after digesting biological matrix with alkali, an ethanol washing step removed significant amount of interferences in pyrolysis GCMS analysis of MNPs (Zhou et al. Environ. Sci. Technol. 55 (5), 2021, 3032-3040; Quantitative Analysis of Polystyrene and Poly(methyl methacrylate) Nanoplastics in Tissues of Aquatic Animals).   Alkali digestion can breakdown natural organic matter into smaller fragments that can interfere with MNP analysis, unless those fragments are removed  by a washing step with a solvent.

The number of studies on MNPs in biological samples is limited. Many researchers have published papers, but the data quality is well documented. For example, Wang et al. (2025) analyzed MNPs in bird lungs treated with HNO3 (https://doi.org/10.1016/j.jhazmat.2025.137274). The chromatogram is very dirty (Fig. 7). Song et al. (2024) compared MNPs concentrations in human urine samples between urban and rural areas (https://doi.org/10.1016/j.scitotenv.2024.170455). This study analyzed MNPs by both number basis (LDIR) and mass basis (PyGCMS). The concept and result are interesting, but the PyGCMS chromatogram presented in supplementary materials showed high-level matrix in the samples (https://ars.els-cdn.com/content/image/1-s2.0-S0048969724005928-mmc1.docx).

 

Very few papers have confirmed removal of all interfering biological matrix components. Sefiloglu et al. (2024) analyzed tilapia filet samples and obtained acceptable matrix effect for PE, PP, PS, and PMMA  (-12% ~ 26%) (https://doi.org/10.1186/s12302-024-00987-6). However, this method optimized mainly for microplastics, not nano-plastics. Zhou et al., (2021) showed lower matrix in GC chromatograms, but this method was optimized for PMMA and PS only and the applicability for other polymers is not known (https://doi.org/10.1021/acs.est.0c08374).

 Nijenhuis et al. (2025) attempted to improve the quantification accuracy of MNPs in human blood samples (https://doi.org/10.1016/j.jhazmat.2025.137584). They used non-target analysis and explored the suitable indicative compounds for quantification with low matrix effect. Currently, enzymatic treatment and hydrogen peroxide decomposition are commonly used for pre-treatment of human blood samples, but Rauert et al. (2025) indicated that those treatment steps are not enough to quantify the trace levels of MNPs fund in human blood samples (https://doi.org/10.1021/acs.est.4c12599).

The biological matrix of plant materials is more difficult to decompose than animal tissues because of the high content of cellulose. Ye et al. (2024) analyzed MNPs in crops, but very high matrix was present in the GC chromatogram in Fig. 3 (https://doi.org/10.1016/j.chemosphere.2024.141689). 

Again, there is no perfect method available yet for the analysis of MNP in biological samples.  A few methods are good for limited types of MNPs, but not more than 3 or 4 types of MNPs.  

By my knowledge, there is no published paper that has yet  demonstrated  without a doubt the complete removal of all interfering biological matrix components, due to the fact that the complexity of such matrices makes this claim scientifically untenable. Instead, there have been reported various protocols that focus on validating the removal of specific targets such as DNA, detergents, or lipids, demonstrating negligible matrix effects within the context of a given assay, and relying on analytical performance metrics to infer that the clean-up is sufficient.

A complete removal of biological matrix components is challenging. The following paper is a relevant study.

Meng et al. (2025) – “A Review of Sources, Hazards, and Removal Methods of Microplastics in the Environment”

No - as far as I am aware such a paper is not available. 

Unfortunately, no. Papers have claimed to have removed interfering components, but have not provided positive proof of such removal.

I am not aware such paper. There are partial methods to mitigate the potential interferences, including the digestion method discussed in this whitepaper. No one has claimed a universal method to minimizing it successfully. Even in human blood, it is not achieved. Assessing the Efficacy of Pyrolysis–Gas Chromatography–Mass Spectrometry for Nanoplastic and Microplastic Analysis in Human Blood | Environmental Science & Technology

No, I cannot think of a paper that has confirmed removal of all interfering biological matrix in microplastics or in any other environmental analytical chemistry of any pollutant. If there was one, I'd be skeptical. 100% removal of matrix isnt expected.