# Why No Lab Can Certify a Product Plastic-Free

> The Wellness Quality Institute explains why no lab can certify plastic-free claims. Understand testing limits & get expert due-diligence guidance.

**Published:** 2026-11-04 | **Updated:** 2026-11-05 | **Author:** mihir
**URL:** https://www.wellnessqualityinstitute.com/articles/microplastics-detection-method-limitations
**Type:** post

**Categories:** Certification

![Why No Lab Can Certify a Product Plastic-Free](https://wellnessquality.sites.aigrowthagent.co/wp-content/uploads/sites/93/2026/11/1793708256424-36a4adb632ac-1024x572.webp)

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## Content

*Written by: Scott Steveson, Specialist, Wellness Quality Institute*

## Key Takeaways

- Microplastics detection methods fail in six distinct ways: contamination, extraction losses, spectroscopic size floors, Py-GC/MS destructiveness, the unvalidated 1–20 µm gap, and non-comparability across labs. Together they mean no method can prove absence.
- Sample contamination can create false positives. Extraction and digestion steps can destroy or miss high-density plastics such as PET and PVC, so low counts stay weak without documented recovery data.
- FTIR and Raman spectroscopy each have practical detection floors, roughly 10–50 µm and about 1 µm, below which particles remain invisible. Py-GC/MS reports polymer mass, not particle counts, size, or shape.
- California’s validated drinking-water methods begin at 20–50 µm. The 1–20 µm fraction and all nanoplastics below 1 µm sit outside reliable commercial measurement and remain unvalidated under current protocols.
- The Wellness Quality Institute reviews existing laboratory data against its WQI-CS-01 standard and verifies what a plastic-related claim can honestly support.

[Explore Plastic-Free Pathway Verification](https://www.wellnessqualityinstitute.com/?utm_term=microplastics-detection-method-limitations&utm_campaign=ai_growth_agent)

## How Sample Contamination Skews Microplastic Results

The first place a microplastics measurement can fail is before the sample reaches an instrument. Airborne fibers, synthetic lab clothing, plastic labware, reagents, and even rinse water are all documented contamination sources in analytical workflows. A March 2026 University of Michigan study in Analytical Methods found that nitrile and latex gloves shed calcium stearate residues whose Raman and infrared spectra closely resemble polyethylene. The study reported roughly 2,000 false particle identifications per square millimeter of contacted surface, enough to inflate counts even in labs that follow standard protocols.

The procedural blank is the control that separates signal from background. A procedural blank is a control sample that passes through every analytical step without the actual sample. It shows contamination introduced by laboratory water, containers, filters, reagents, and handling. When blanks are inadequate, the reported number measures the lab environment plus the sample, with no way to separate the two.

A 2024 PNAS study by [Qian et al. (Columbia University)](https://www.pnas.org/doi/10.1073/pnas.2300582121) illustrates this failure clearly. The study reported about 240,000 plastic particles per liter of bottled water, with roughly 90% classified as nanoplastics. The figure drew wide attention and a formal critique. [Dušan Materić, writing in PNAS](https://www.pnas.org/doi/10.1073/pnas.2411099121), argued that the study’s own Milli-Q procedural blanks showed plastic contamination comparable to the bottled water samples. The authors instead used clean Anodisc filters as the reference. Materić’s analysis showed that every bottled water sample fell below the concentration of the procedural blank, so the headline figure was not supported by the study’s own quality-control data. The original authors [replied in the same issue](https://www.pnas.org/doi/10.1073/pnas.2415874121) and defended their blank selection on the grounds that Milli-Q water was itself contaminated. The disagreement remains unresolved in the published record.

![Fragments of plastic suspended in blue water below the surface.](https://cdn.aigrowthmarketer.co/1784829388732-c6255482b477.webp)**Plastic doesn’t disappear — it fragments. These secondary microplastics are the breakdown products of everyday objects, and independent research now detects them across the water supply. Detection, though, establishes presence, not absence.**

The takeaway is narrower: a number without its blank data is not yet a measurement.

[For more on how detection floors shape what a result can mean, see Microplastics Detection Floor: What Lab Results Really Mean.](https://www.wellnessqualityinstitute.com/articles/detection-floor-microplastics-analysis/?utm_term=microplastics-detection-method-limitations&utm_campaign=ai_growth_agent)

## Extraction And Digestion Losses That Hide Plastic

Sample preparation can remove the very particles a lab wants to measure. Before a sample reaches any instrument, technicians digest biological tissue, remove organic matter, and concentrate and separate particles. Each step can lose particles.

Density separation is the most common extraction approach. It floats plastic particles in a salt solution while denser material sinks. [Saturated sodium chloride (NaCl), the most widely used medium at roughly 1.15–1.30 g/cm³](https://mdpi.com/2071-1050/18/18/9537/review_report), cannot float high-density polymers such as PET (1.37–1.41 g/cm³) or PVC (1.38–1.45 g/cm³). Those polymers settle with the mineral fraction and never reach the instrument. Any study using only NaCl therefore undercounts PET and PVC, two of the most commercially important plastics, even when everything else is done carefully.

![Colorful plastic fragments in water inside a laboratory petri dish.](https://cdn.aigrowthmarketer.co/1784829410323-fb401fc7b1e4.webp)**Microplastics are particles smaller than five millimeters. Current methods can count and identify them at the upper end of that range, but reliable measurement falls away as particles get smaller — a limit that shapes every honest claim.**

Digestion chemistry creates different losses. PET is particularly vulnerable to alkaline digestion. [A 2026 comparative review in Sustainability](https://mdpi.com/2071-1050/18/18/9537) documented significantly greater PET weight loss at higher KOH concentrations, with one protocol reporting degradation under conditions widely used in the field. PVC behaves differently. Certain acid concentrations leave particle size and color unchanged, yet the FTIR spectrum, the chemical fingerprint used to identify the polymer, deteriorates. The particle survives digestion but becomes unidentifiable, which creates a false negative driven by preparation, not absence.

Recovery variability compounds these problems. A [2026 inter-laboratory comparison in Scientific Reports](https://link.springer.com/article/10.1038/s41598-026-64477-w), involving seven laboratories across seven countries using a harmonized extraction protocol, found that polyethylene recovery from spiked matrices ranged from below 5% to above 130% depending on the laboratory and matrix. Seven of eight laboratories reported soil recoveries below 80%. The protocol and reference material stayed the same. The results did not.

A low particle count in a lab report may reflect a clean product or extraction losses. Without recovery data, meaning spike-recovery experiments that show how much of a known added quantity the method retrieves, no one can tell which explanation fits.

## What FTIR And Raman Cannot See

The two dominant spectroscopic methods for microplastics identification each have a size floor below which particles remain invisible.

Micro-FTIR, or Fourier transform infrared spectroscopy, is diffraction-limited. [Hossain et al. in Micro (MDPI)](https://mdpi.com/2673-8023/6/3/50) report a practical detection floor of roughly 10–20 µm. [A 2026 MAPAN critical review](https://link.springer.com/10.1007/s12647-026-00943-0) reports about 20–50 µm for FTIR. Both describe these as operational limits, not fixed instrument specifications. Particles smaller than that floor are not detected because the instrument cannot resolve them.

Raman spectroscopy uses a shorter excitation wavelength and can resolve particles approaching 1 µm. That capability is a real advantage, but it has limits. Fluorescence interference, where the sample emits light that drowns out the Raman signal, reduces usable sensitivity, especially for weathered, pigmented, or biologically coated particles. Spectral library quality also matters. The instrument can only identify a polymer if its reference library contains a matching spectrum. A polymer missing from the library produces no match, which looks like a negative result.

A [2026 seven-country inter-laboratory comparison in Scientific Reports](https://link.springer.com/article/10.1038/s41598-026-64477-w) found that polymer identification accuracy ranged from 54.4% to 93.3% across laboratories analyzing identical pristine polymer standards. Polypropylene, one of the most widely produced polymers, was misidentified in almost all participating countries. A single laboratory’s reference library update raised its identification accuracy from 58% to 93% for the same particles. The instrument stayed the same. The library changed.

Below each method’s floor, “not found” and “not there” describe different realities. The instrument simply did not look.

[For a comparison of FTIR, Raman, and Py-GC/MS analytical approaches, see Microplastics Analysis Techniques: FTIR, Raman & Py-GC/MS.](https://www.wellnessqualityinstitute.com/articles/microplastics-analysis-techniques-comparison/?utm_term=microplastics-detection-method-limitations&utm_campaign=ai_growth_agent)

[See how Plastic-Free Pathway Verification scopes a claim to what your data supports](https://www.wellnessqualityinstitute.com/?utm_term=microplastics-detection-method-limitations&utm_campaign=ai_growth_agent)

## Why Py-GC/MS Cannot Count Particles

Pyrolysis–gas chromatography/mass spectrometry, or Py-GC/MS, measures polymer mass by destroying the sample. The method heats a sample until its polymers thermally decompose, then identifies the breakdown products by their chemical signatures. It is sensitive, works in complex matrices where spectroscopic methods struggle, and can detect polymer mass below the size floors of FTIR and Raman.

Destructiveness is the tradeoff. The sample is consumed, and every detail about particle number, size, shape, and location disappears. A Py-GC/MS result reports polymer mass only. It cannot show whether that mass came from a few large fragments or millions of submicron particles. It cannot show what the particles looked like, where they concentrated in the sample, or whether they were solid particles at all. Dissolved or non-particulate polymer-associated material contributes to the mass signal unless the separation step is clearly defined and validated.

[A 2026 review in the Journal of Xenobiotics](https://pmc.ncbi.nlm.nih.gov/articles/PMC13514148) notes that no current analytical method captures particle number, polymer mass, shape, nanoscale fraction, surface chemistry, and anatomical localization in one workflow. Each method answers only part of the question.

Particle count and polymer mass answer different questions. A report that provides one cannot stand as evidence about the other.

## The Nanoplastic Gap And The Unvalidated 1–20 µm Fraction

The size range that current methods cannot reliably measure creates the most serious blind spot for plastic-related claims.

California’s drinking-water microplastics definition, the strictest public regulatory reference in use today, covers solid polymeric material with particles that have at least three dimensions greater than 1 nanometer and less than 5,000 micrometers. That range spans from nanoscale fragments to visible pieces. The two analytical methods that California’s State Water Board has validated cover only part of this range:

- SWB-MP1-rev1, an infrared spectroscopy method, validated for particles greater than 50 µm through 5,000 µm
- SWB-MP2-rev1, a Raman spectroscopy method, validated for particles greater than 20 µm through 5,000 µm

The regulation reaches to 1 nanometer while the best validated methods begin at 20 or 50 micrometers, which are thousands of times larger. The 1–20 µm fraction is not validated under either method. Everything below 1 µm, the entire nanoplastic domain, sits beyond reliable commercial measurement. A detailed 2026 analysis of drinking-water microplastics monitoring confirms that California’s framework specifies infrared spectroscopy for particles at or above 50 µm and Raman for particles at or above 20 µm, leaving the 1–20 µm fraction without a specified identification technique.

No method currently bridges the definition and the measurement. Any claim evaluated against the California framework, or any similar regulatory definition, therefore describes only a fraction of the size range that the definition covers. That boundary reflects the current state of the science.

[For a full explanation of what a “none detected” result means in this context, see What “None Detected” Really Means In Microplastics Testing.](https://www.wellnessqualityinstitute.com/articles/none-detected-microplastics-meaning/?utm_term=microplastics-detection-method-limitations&utm_campaign=ai_growth_agent)

## Why Microplastic Measurements Differ Across Labs

Two laboratories can test the same sample and report numbers that do not line up. This gap reflects structural differences in methods, not simple quality problems.

The sources of non-comparability include different lower size cutoffs, reporting units, reference spectral libraries, digestion and extraction protocols, and blank-correction approaches. A [2026 systematic review in Environmental Science and Pollution Research](https://link.springer.com/article/10.1007/s11356-026-38311-9) that synthesized 40 observational studies found substantial methodological heterogeneity across µFTIR, µ-Raman, LDIR, and Py-GC/MS workflows, including differences in analytical techniques, reporting units, and limits of detection.

A lab that reports particles above 10 µm will always find more particles than a lab that reports above 100 µm, even when they test identical samples. The smaller cutoff simply includes more particles.

Standardization efforts are underway. ISO 16094-2:2025 provides guidelines for vibrational spectroscopy methods in low-suspended-solids waters and covers a particle-size range from about 1 µm to 5,000 µm. [ISO 24187:2023](https://www.iso.org/standard/78033.html) sets out general analytical principles across environmental matrices. The European Commission’s PlasticsFatE project, in its first policy brief (December 2024), identified the lack of standardized methods, including harmonized sampling, processing, and analysis protocols and global reference materials, as a barrier that has led to inconsistent data and limited risk assessment. A [2026 perspective synthesizing the FHERITALE project outputs](https://link.springer.com/article/10.1186/s40550-026-00159-9) describes persistent standardization gaps across laboratory workflows. These standards offer frameworks organizations may choose to reference. They do not function as universal mandates, and adoption varies by jurisdiction and matrix.

Until harmonization improves, a lab report that lists only the instrument type, such as FTIR, Raman, or Py-GC/MS, does not establish the size or concentration floor needed to interpret a negative result. The operational size window, polymer panel, sample preparation protocol, blank correction, and reporting units together determine what the number means.

## How Detection Limits Shape A Plastic-Related Claim

The six failure modes above lead to one practical reality. Detection can show presence, but it cannot prove absence. Proving absence would require ruling out every particle below the detection floor, every polymer outside the tested panel, and every unsampled production lot. No current method can do that completely.

“None detected” means none found above that instrument’s floor, for the polymers it screened, in the lot it tested. A defensible claim scopes itself to the method, tested particle-size range, polymer panel, and production period. It stays silent about what lies outside those boundaries.

The Wellness Quality Institute enters at this point in the process. The Wellness Quality Institute is an independent verification body that reviews a company’s existing third-party laboratory data on plastic and microplastic content against a defined standard, WQI-CS-01. This standard aligns with the California State Water Board’s drinking-water microplastics reference framework as a technical reference point, not as a geographic requirement or government endorsement. The Wellness Quality Institute does not run laboratory tests. Its team reviews whether the method suited the product or matrix, whether reporting limits were adequate, whether blanks and controls were run, and what claim the data can support.

![Scientists in white coats working with samples and microscopes in a laboratory.](https://cdn.aigrowthmarketer.co/1784829434095-0fc8fbcf29fa.webp)**Only a small number of laboratories can genuinely test for microplastics, and capability varies by instrument and method. WQI reviews a company’s existing third-party laboratory data against a defined standard — it does not run the tests itself.**

A Standard Met outcome under the Wellness Quality Institute’s Plastic-Free Pathway Verification provides a scope-locked license to use the approved mark, a public registry listing, and approved claim language tied to the specific reviewed evidence. A Standard Not Met outcome remains private and can be resubmitted with updated information. Every verified claim links to a registry entry that records the verified product, tested size range, polymer panel, production period, and lower method limit. Anyone can check the claim against the evidence.

*The Wellness Quality Institute Plastic-Free Pathway Verification does not certify that a product contains zero plastic, microplastics, or nanoplastics. It shows that the company is on a verified pathway toward plastic-free standards. Verification applies only to the reviewed products, submitted datasets, tested ranges, polymer panels, production or sampling periods, and supporting controls. The Wellness Quality Institute verification is not a California approval, government certification, or health or safety certification.*

## How Companies Commonly Support Plastic-Related Claims

Because a lab result alone cannot prove absence, companies must decide how to present what their data does show. Four approaches appear most often, and they differ mainly in how much independent scrutiny stands behind the claim.

- **Independent third-party review of the dataset against a published standard**. The Wellness Quality Institute’s Plastic-Free Pathway Verification review against WQI-CS-01 fits this category. An independent party with no stake in the outcome reviews the method, controls, and data, then issues scope-locked claim language. The claim is checkable through a public registry.
- **Raw lab report published directly**. The data is real, but no independent party has assessed whether the method suited the matrix, whether the reporting limits were adequate, or what the result can support. The market reads this as a self-reported claim.
- **Internal “we tested it” claim**. The work may be rigorous or minimal. Either way, it carries the credibility of a company grading its own homework. The commercial interest in the outcome is clear.
- **Silence**. Many brands with genuine data say nothing because legal teams cannot approve a claim they cannot defend. Real progress then stays invisible.

[Turn your lab data into a claim you can defend](https://www.wellnessqualityinstitute.com/?utm_term=microplastics-detection-method-limitations&utm_campaign=ai_growth_agent)

## Risks, Constraints, And A Practical Due-Diligence Checklist

Anyone evaluating a lab report or a plastic-related claim can use a simple checklist. A defensible result names each of these elements explicitly.

- The analytical method and its validated size range, not just the instrument name
- Reporting limits, meaning the lowest concentration the method can reliably quantify
- Blank and spike-recovery data, which show that contamination was controlled and that extraction recovered particles
- Chain of custody, which documents that the sample stayed intact between collection and analysis
- The polymer panel, meaning which specific polymers were screened
- The specific product and production period covered

Practical constraints shape every testing program. Microplastics analysis is expensive, laboratory capacity is limited, and results stay bounded by the method used. Verification scope remains narrow by design. A single product’s result does not extend to a full product line or an entire company. Standards also evolve. Methods that count as adequate today may change as ISO and regulatory frameworks mature.

## Conclusion: Why No Lab Can Certify A Product Plastic-Free

The limitations of microplastics detection methods explain why no laboratory can certify a product plastic-free and why any honest claim must be scoped to method, size range, and polymer panel. Contamination can inflate counts. Extraction losses can suppress them. Spectroscopic floors leave entire size fractions invisible. Py-GC/MS measures mass but not particles. The 1–20 µm fraction remains unvalidated under the best available methods, and the nanoplastic domain sits beyond reliable commercial measurement. Two labs testing the same sample can produce numbers that do not compare.

A claim that survives scrutiny states its boundaries clearly. It says: none detected above this floor, using this method, for these polymers, in this lot, with documented controls and independent review. That framing turns a raw number into a measurement and a bare statement into a claim.

[See how Plastic-Free Pathway Verification supports scoped, defensible claims](https://www.wellnessqualityinstitute.com/?utm_term=microplastics-detection-method-limitations&utm_campaign=ai_growth_agent)

## What to Read Next

- [Why Most Plastic-Free Microplastics Claims Don’t Hold Up?](https://www.wellnessqualityinstitute.com/articles/water-quality-month-detection-limits/)
- [How to Test for Microplastics: Methods, Limits & Labs](https://www.wellnessqualityinstitute.com/articles/microplastic-testing-methods/)
- [What Microplastics Testing Proves and Where It Stops](https://www.wellnessqualityinstitute.com/articles/what-microplastics-testing-proves/)
- [Why Labs Can’t Prove Water Is Plastic-Free](https://www.wellnessqualityinstitute.com/articles/water-quality-month-importance/)
- [What Your Microplastics Lab Report Actually Proves](https://www.wellnessqualityinstitute.com/articles/independent-review-lab-results-microplastics/)

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- **Headline:** Why No Lab Can Certify a Product Plastic-Free
- **Description:** The Wellness Quality Institute explains why no lab can certify plastic-free claims. Understand testing limits & get expert due-diligence guidance.
- **DateModified:** 2026-11-03T12:17:24.393Z
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  - **Description:** Scott Stevenson is part of the Wellness Quality Institute team, where he supports WQI’s work to advance product transparency, credible verification, and greater consumer trust. His background spans ethics and compliance, corporate trust, and responsible business, including experience with Ethisphere Institute and global companies navigating evolving standards and stakeholder expectations.
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## Citations

- [Plastic Claim Substantiation: Evidence Before You Claim](https://www.wellnessqualityinstitute.com/articles/plastic-claim-substantiation-evidence-requirements)
- [How To Make Plastic Reduction Claims That Hold Up](https://www.wellnessqualityinstitute.com/articles/substantiate-clean-label-plastic-reduction)
- [Plastic Claim Substantiation: A US Compliance Guide](https://www.wellnessqualityinstitute.com/articles/plastic-claim-substantiation-compliance-guide)
- [Microplastics Verification Standards: A Complete Guide](https://www.wellnessqualityinstitute.com/articles/microplastics-verification-standards-guide)
- [What Microplastic Test Results Actually Mean](https://www.wellnessqualityinstitute.com/articles/what-microplastic-testing-actually-proves)

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