Clarification of question 1.8: Are there reliable sources of reference particles for spiking into matrices for recovery studies that are representative of particles expected to be found in the environment in terms of size, shape, chemistry, etc.? (please provide sources if possible)

Answer Explanations

• Yes

  Expert 9
  We have used PE MPs particles available from Cospheric™, California, USA.
• No

  Expert 3
  The extreme level of complexity of these materials in the environment cannot be adequately replicated in (commercially) available reference materials. There are just too many degrees of weathering (and different types of weathering) that result in morphological and surface chemistry alterations, types and extent of sorbed contaminants, variability of additives (and their relative composition), etc... This cannot be suitably mimicked. 
• Yes

  Expert 2
  Yes, there are some reliable sources of reference particles for recovery studies, although there are ongoing studies on this and the options are still evolving. Some certified reference materials have just recently become available, such as the EU’s EURM-060, the first certified microplastic material in a water matrix, designed to improve method validation and interlaboratory comparability (https://crm.jrc.ec.europa.eu/s/20/Weblog/b/628/EURM-060-new-reference-material-for-the-analysis-of-microplastic-particles).  Alos, there are national metrology institutes  that periodically provide valuable options: for example, BAM in Germany developed BAM-P206 (https://rrr.bam.de/RRR/Content/EN/Standard-Articles/Reference-Materials/RM-News/rm-news-bam-p206.html ),  a PET powder that could be suitable for validating sampling and detection in environmental matrices. On the other hand, NIST from the US offers a wide range of standard reference materials, including well-defined polystyrene spheres and gold nanoparticles (SRMs 8011–8013), (https://tsapps.nist.gov/srmext/certificates/archives/8013.pdf ) which are highly useful for recovery and size validation even though they are spherical and less environmentally realistic. Recently, almost all of the commercial suppliers have also begun producing certified microplastic standards. For example, Chiron AS/BCP Instruments provides CRM tablets comprising multiple polymers for routine quality control. In addition, initiatives like the EU PlasticTrace project are developing micro and nanoplastic materials designed to mimic real environmental particles in terms of size, shape, polymer type, and degradation state, addressing current gaps in availability of fibers, irregular fragments, and weathered particles. In practice, EURM-060 is  the most appropriate for general recovery studies in water matrices, BAM-P206 for irregular fragments in the 10–200 µm range, NIST nanoparticle and microsphere standards for size-based recovery validation, and commercial CRMs like those from Chiron for routine spiking and QC. 
  
  
  
• Expert 7
  I do not have personal experience about this question. However, my searching suggests that there are some reliable sources of reference microplastic particles suitable for spiking into biological matrices for recovery study.  These materials are designed to mimic environmental microplastics in terms of size, shape, polymer chemistry, and behavior, and are increasingly being tailored for use in complex matrices like tissues, fluids, and food products.
  
  1. Microplastic Solution – EasyMP™ Standards

  
  Microplastic Solution offers a wide range of customizable microplastic reference materials under the EasyMP™ brand:
  
  

  • Particle types: Fragments, fibers, and beads
  • Size range: 10–1000 µm
  • Formats: Liquid suspensions or dry powders
  • Polymers: PE, PP, PET, PS, PVC, PC, and mixed compositions
  • Matrix compatibility: Designed for use in biological matrices such as tissues and fluids
  • Quality assurance: RSD < 20% in line with EUROqCHARM standards

  They also offer Py-GC/MS calibration standards with sieved fragments <15 µm for quantitative pyrolysis analysis, which are particularly useful for biological sample validation 

  
  2. Springer Study – Soda Tablets and Gelatin Capsules
  
  

  A peer-reviewed study published in Analytical and Bioanalytical Chemistry describes the development of soda tablets and gelatin capsules containing microplastics for interlaboratory comparison and recovery testing:
  
  

  • Polymers included: PE, PET, PS, PVC, PP, PC
  • Size range: 50–1000 µm
  • Application: Used successfully in biological and environmental matrices
  • Recovery performance: RSDs between 8–21%, with 100% recovery in some cases 

  These formats are particularly useful for controlled dosing and easy integration into biological samples.
  
  

  3. Fluorescent PET Fragments for Drinking Water Studies

  
  A study in Microplastics and Nanoplastics developed Nile red-stained PET fragments as fluorescent reference materials:
  
  

  • Size range: <20 µm
  • Stability: Fluorescence stable over 4 months
  • Matrix compatibility: Validated for use in aqueous and biological matrices
  • Recovery performance: RSD of 2.5% among replicates 

  These are especially useful for visual tracking and fluorescence-based recovery studies in biological systems.
  
  
• No

  Expert 1
  I don't think that there are reference MNP particles of various colors, size and shape available for spiking into sample matrices.   This is important for spectroscopy based methods, but not for pyrolysis GCMS method. 
  
  For GC-MS based methods, characterized particles are commercially available.  For example, nano size particles made of polystyrene (PS) and polymethyl methacrylate (PMMA) are available (Non-functionalized Polystyrene - Bangs Laboratories, Inc.). Micro size particles of PE and PVC are commercially available (e.g., Cospheric LLC, Santa Barbara, CA, USA; Polyethylene Nanospheres 200nm-9900nm (1-10um) for environmental studies of microplastic pollutants). However, currently,  nano-size particle standards of those polymers except PS and PMMA are not available. Even when such nanoparticles are produced, the purities low in the range of 50-70%.  This article can make a recommendation about analytical standards for MNPs.  Commercial vendors should make micro and nano sized MNPs of various types for help with harmonizing quantification.
• Yes

  Expert 4
  I would like to refer to the following paper in which detailed case studies are provided:
  Korinna Altmann, Lukas Wimmer, Victor Alcolea-Rodriguez, et al. Quality-by-design and current good practices for the production of test and reference materials for micro- and nano-plastic research. Journal of Hazardous Materials,
  497, 139595, 2025. https://doi.org/10.1016/j.jhazmat.2025.139595.
  Thereupon, the Joint Research Centre of the European Union is developing reference materials:
  EU Launches First Certified Reference Material for Microplastic Analysis | Plastics Engineering
  Finally, NIST is developing refrence particles:
  Reference Materials for Plastic Pollution Measurement Science | NIST
• No

  Expert 5
  The answer could be 'Yes' if the categorizations are very limited. For example: shape -- fiber, flake, fragment. Otherwise there are too many variables. For example: chemistry -- monomer type, polymer molecular weight distribution, additives, entrained contaminants, weathering, etc. 
  "...that are representative of particles expected to be found..." is very difficult because microplastic particles often have vastly different environmental histories.
• No

  Expert 6
  There are no reliable sources of material meeting all size, shape and plastic chemistry at the same time. The most difficult aspect is shape. In the environment, the shape of particles is observed random. However, there are sources of particles with some characteristics.
  1. Frontier lab offers microplastics with plastic chemistry information and concentration. Microplastics Calibration Standard set | Multi-Functional Pyrolysis System | Products | Frontier Laboratories
  2. HPU offers polymer standards with plastic chemistry information. polymerkit1.0_marketingbrochure.pdf
  3. Cospheric offers (Microspheres, Nanospheres, Precision Spherical Particles - Cospheric Ships Globally - US-based Manufacturer) MNPs with well defined size. In terms of shape, Cospheric offers all spheres for materials. Whether perfect sphere is good representation for MNP studies is to be debated. 
• Yes

  Expert 8
  My answer would be yes and no. For biological tissues, particles less than 10 um should be used. There are PS spheres available from NIST and other commercial sources, but reliable sources aren't available for representative particles of this size in an irregular shape nor from a large diversity of polymers.