{"id":60,"date":"2026-08-14T05:01:55","date_gmt":"2026-08-14T05:01:55","guid":{"rendered":"https:\/\/www.wellnessqualityinstitute.com\/articles\/microplastics-testing-methodology-validation"},"modified":"2026-08-26T05:02:20","modified_gmt":"2026-08-26T05:02:20","slug":"microplastics-testing-methodology-validation","status":"publish","type":"post","link":"https:\/\/www.wellnessqualityinstitute.com\/articles\/microplastics-testing-methodology-validation","title":{"rendered":"Microplastics Testing Methodology Validation Guide"},"content":{"rendered":"<p><em>Written by: Scott Steveson, Specialist<\/em><\/p>\n<h2>Key Takeaways<\/h2>\n<ul>\n<li>\n<p>Method validation makes microplastics claims defensible because raw lab data alone cannot survive independent review without documented recovery rates, blank correction, and defined detection limits.<\/p>\n<\/li>\n<li>\n<p>Core validation parameters include spiking recovery of 70\u2013130% (90% or higher preferred for PE, PP, PS), precision at or below 20% relative standard deviation, and empirically established detection and quantification limits for Raman and FTIR methods.<\/p>\n<\/li>\n<li>\n<p>Three blank types are required for credible data: field, procedural, and air blanks, with both raw and blank-corrected counts reported by polymer and size fraction.<\/p>\n<\/li>\n<li>\n<p>WQI-CS-01 review criteria from The Wellness Quality Institute align directly with these validation parameters and require accredited laboratories plus a minimum polymer panel covering PE, PP, PET, PS, PVC, PA, PC, and PMMA.<\/p>\n<\/li>\n<li>\n<p>The Wellness Quality Institute helps brands turn validated laboratory data into defensible claims through Plastic-Free Pathway Verification; <a target=\"_blank\" rel=\"noopener noreferrer nofollow\" href=\"https:\/\/www.wellnessqualityinstitute.com\">learn more about Plastic-Free Pathway Verification<\/a>.<\/p>\n<\/li>\n<\/ul>\n<h2>Core Validation Parameters for Microplastics Testing<\/h2>\n<p>The table below summarizes the key validation parameters drawn from ISO 24187:2023 and the California State Water Board analytical methods SWB-MP1-rev1 and SWB-MP2-rev1, which together form a practical framework many organizations now follow. These benchmarks highlight a consistent pattern: spectroscopic methods need detection limits proven with real samples, and recovery must be shown for each target polymer instead of assumed from a single reference material.<\/p>\n<figure style=\"text-align: center\"><img decoding=\"async\" src=\"https:\/\/cdn.aigrowthmarketer.co\/1784829410323-fb401fc7b1e4.webp\" alt=\"Colorful plastic fragments in water inside a laboratory petri dish.\" style=\"max-height: 500px\" loading=\"lazy\"><figcaption><em>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 \u2014 a limit that shapes every honest claim.<\/em><\/figcaption><\/figure>\n<table style=\"min-width: 100px\">\n<colgroup>\n<col style=\"min-width: 25px\">\n<col style=\"min-width: 25px\">\n<col style=\"min-width: 25px\">\n<col style=\"min-width: 25px\"><\/colgroup>\n<tbody>\n<tr>\n<th colspan=\"1\" rowspan=\"1\">\n<p>Parameter<\/p>\n<\/th>\n<th colspan=\"1\" rowspan=\"1\">\n<p>Accepted Benchmark<\/p>\n<\/th>\n<th colspan=\"1\" rowspan=\"1\">\n<p>Method Context<\/p>\n<\/th>\n<th colspan=\"1\" rowspan=\"1\">\n<p>Primary Reference<\/p>\n<\/th>\n<\/tr>\n<tr>\n<td colspan=\"1\" rowspan=\"1\">\n<p>Spiking recovery<\/p>\n<\/td>\n<td colspan=\"1\" rowspan=\"1\">\n<p>70\u2013130% (target); 90% or higher preferred for PE, PP, PS in water matrices<\/p>\n<\/td>\n<td colspan=\"1\" rowspan=\"1\">\n<p>All spectroscopic methods<\/p>\n<\/td>\n<td colspan=\"1\" rowspan=\"1\">\n<p>ISO 24187:2023; <a target=\"_blank\" rel=\"noindex nofollow\" href=\"https:\/\/pmc.ncbi.nlm.nih.gov\/articles\/PMC12930080\">Pereira et al., 2026<\/a><\/p>\n<\/td>\n<\/tr>\n<tr>\n<td colspan=\"1\" rowspan=\"1\">\n<p>Precision (RSD)<\/p>\n<\/td>\n<td colspan=\"1\" rowspan=\"1\">\n<p>20% relative standard deviation or lower across replicates<\/p>\n<\/td>\n<td colspan=\"1\" rowspan=\"1\">\n<p>All methods<\/p>\n<\/td>\n<td colspan=\"1\" rowspan=\"1\">\n<p>ISO 24187:2023; <a target=\"_blank\" rel=\"noindex nofollow\" href=\"https:\/\/publications.jrc.ec.europa.eu\/repository\/handle\/JRC146755\">JRC146755, 2026<\/a><\/p>\n<\/td>\n<\/tr>\n<tr>\n<td colspan=\"1\" rowspan=\"1\">\n<p>LOD\/LOQ, Raman<\/p>\n<\/td>\n<td colspan=\"1\" rowspan=\"1\">\n<p>Empirically established, with a practical lower limit often above 20 \u00b5m in complex matrices<\/p>\n<\/td>\n<td colspan=\"1\" rowspan=\"1\">\n<p>SWB-MP2-rev1 (Raman); validated range above 20 \u00b5m to 5,000 \u00b5m<\/p>\n<\/td>\n<td colspan=\"1\" rowspan=\"1\">\n<p>SWB-MP2-rev1; <a target=\"_blank\" rel=\"noindex nofollow\" href=\"https:\/\/mdpi.com\/1420-3049\/31\/15\/2675\">Vega-Baudrit et al., 2026<\/a><\/p>\n<\/td>\n<\/tr>\n<tr>\n<td colspan=\"1\" rowspan=\"1\">\n<p>LOD\/LOQ, FTIR<\/p>\n<\/td>\n<td colspan=\"1\" rowspan=\"1\">\n<p>Empirically established from procedural blanks; validated range above 50 \u00b5m to 5,000 \u00b5m<\/p>\n<\/td>\n<td colspan=\"1\" rowspan=\"1\">\n<p>SWB-MP1-rev1 (infrared); \u00b5-FTIR<\/p>\n<\/td>\n<td colspan=\"1\" rowspan=\"1\">\n<p>SWB-MP1-rev1; <a target=\"_blank\" rel=\"noindex nofollow\" href=\"https:\/\/mdpi.com\/1420-3049\/31\/13\/2237\">Rodrigues et al., 2026<\/a><\/p>\n<\/td>\n<\/tr>\n<tr>\n<td colspan=\"1\" rowspan=\"1\">\n<p>Blank correction<\/p>\n<\/td>\n<td colspan=\"1\" rowspan=\"1\">\n<p>Field, procedural, and air blanks required; raw and corrected counts both reported<\/p>\n<\/td>\n<td colspan=\"1\" rowspan=\"1\">\n<p>All methods<\/p>\n<\/td>\n<td colspan=\"1\" rowspan=\"1\">\n<p><a target=\"_blank\" rel=\"noindex nofollow\" href=\"https:\/\/pmc.ncbi.nlm.nih.gov\/articles\/PMC12981036\">Kamalasekaran &amp; Sundramoorthy, 2026<\/a><\/p>\n<\/td>\n<\/tr>\n<tr>\n<td colspan=\"1\" rowspan=\"1\">\n<p>Spectral library match<\/p>\n<\/td>\n<td colspan=\"1\" rowspan=\"1\">\n<p>Confidence above 75% against reference spectra for polymer identification<\/p>\n<\/td>\n<td colspan=\"1\" rowspan=\"1\">\n<p>FTIR; Raman<\/p>\n<\/td>\n<td colspan=\"1\" rowspan=\"1\">\n<p><a target=\"_blank\" rel=\"noindex nofollow\" href=\"https:\/\/pmc.ncbi.nlm.nih.gov\/articles\/PMC12930080\">Pereira et al., 2026<\/a><\/p>\n<\/td>\n<\/tr>\n<tr>\n<td colspan=\"1\" rowspan=\"1\">\n<p>Interlaboratory reproducibility<\/p>\n<\/td>\n<td colspan=\"1\" rowspan=\"1\">\n<p>Method-dependent; reproducibility (SR) must be quantified and reported<\/p>\n<\/td>\n<td colspan=\"1\" rowspan=\"1\">\n<p>All methods<\/p>\n<\/td>\n<td colspan=\"1\" rowspan=\"1\">\n<p><a target=\"_blank\" rel=\"noindex nofollow\" href=\"https:\/\/iris.inrim.it\/handle\/11696\/88180\">VAMAS ILC, 2025<\/a><\/p>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<h2>Step-by-Step Validation Protocol for Microplastics Methods<\/h2>\n<p>This protocol reflects practices documented in ISO 24187:2023, the California SWB methods, and current peer-reviewed literature. It serves as a practical reference framework, not a regulatory requirement. Brands and laboratories should confirm which elements apply to their specific product type, test method, and intended claim.<\/p>\n<figure style=\"text-align: center\"><img decoding=\"async\" src=\"https:\/\/cdn.aigrowthmarketer.co\/1784829434095-0fc8fbcf29fa.webp\" alt=\"Scientists in white coats working with samples and microscopes in a laboratory.\" style=\"max-height: 500px\" loading=\"lazy\"><figcaption><em>Only a small number of laboratories can genuinely test for microplastics, and capability varies by instrument and method. WQI reviews a company&#8217;s existing third-party laboratory data against a defined standard \u2014 it does not run the tests itself.<\/em><\/figcaption><\/figure>\n<ol>\n<li>\n<p><strong>Sampling design.<\/strong> Define the product matrix, sampling volume, number of replicates, and sampling locations before any laboratory work begins. Sampling design determines what the result can represent. A single-lot, single-volume sample supports only that lot, not a product line. Document chain of custody from sample collection through analysis.<\/p>\n<\/li>\n<li>\n<p><strong>Extraction and density separation.<\/strong> Select a density-separation solution that matches the target polymer panel. <a target=\"_blank\" rel=\"noindex nofollow\" href=\"https:\/\/pmc.ncbi.nlm.nih.gov\/articles\/PMC13056732\">Lo Bue et al. (2026)<\/a> showed that sodium iodide solution at 1.70 g\/cm\u00b3 achieved mean recovery of 86.33 \u00b1 8.20% across PET, PP, and PVC. Sodium chloride at 1.18 g\/cm\u00b3 left PET, with density around 1.38 g\/cm\u00b3, largely unrecovered at 36.5 \u00b1 4.47%. Panels that include PET or PVC therefore need higher-density separation media. <a target=\"_blank\" rel=\"noindex nofollow\" href=\"https:\/\/pmc.ncbi.nlm.nih.gov\/articles\/PMC13388355\">Da Silva de Aquino et al. (2026)<\/a> confirmed that zinc chloride at 1.8 g\/cm\u00b3 floated all six tested polymers, including PET and PVC, in wastewater matrices. Document the separation medium, density, temperature, and number of extraction cycles.<\/p>\n<\/li>\n<li>\n<p><strong>Spiking recovery experiments with PE, PP, and PS benchmarks.<\/strong> Spike known quantities of reference microplastic particles, at minimum PE, PP, and PS, into the sample matrix before extraction. Run at least three replicates. The target acceptance window is 70\u2013130% recovery, with 90% or higher achievable and preferred for these polymers in water matrices. <a target=\"_blank\" rel=\"noindex nofollow\" href=\"https:\/\/pmc.ncbi.nlm.nih.gov\/articles\/PMC12930080\">Pereira et al. (2026)<\/a> found that PE, PP, and PS maintained greater than 90% recovery with no significant spectral changes across all tested conditions. Recovery below 70% or above 130% requires method investigation before reporting results. Precision across replicates should not exceed 20% relative standard deviation, meaning the spread of replicate results, as a percentage of the average, should stay at or below 20%.<\/p>\n<\/li>\n<li>\n<p><strong>Blank-correction protocols by polymer and size fraction.<\/strong> Run field blanks, procedural blanks, and air blanks with each batch. Field blanks follow the full sampling procedure in the field. Procedural blanks follow the full laboratory workflow. Air blanks use open containers exposed during analysis to capture airborne fibers. Report raw particle counts and blank-corrected counts separately for each polymer type and each size fraction. <a target=\"_blank\" rel=\"noindex nofollow\" href=\"https:\/\/pmc.ncbi.nlm.nih.gov\/articles\/PMC12981036\">Kamalasekaran and Sundramoorthy (2026)<\/a> specify that results must include the mean and standard deviation of particles detected in blanks, with a clear statement on whether blank correction was applied. Reviews of published microplastic studies show limited compliance with contamination-control parameters, which directly weakens the defensibility of reported results.<\/p>\n<\/li>\n<li>\n<p><strong>LOD and LOQ establishment for Raman and FTIR.<\/strong> The limit of detection (LOD) is the smallest amount a method can reliably detect. The limit of quantification (LOQ) is the smallest amount it can reliably measure. Both must be established with real data for each method and matrix combination, not assumed from instrument specifications. For \u00b5-FTIR, <a target=\"_blank\" rel=\"noindex nofollow\" href=\"https:\/\/mdpi.com\/1420-3049\/31\/13\/2237\">Rodrigues et al. (2026)<\/a> established a method detection limit from procedural blanks containing zero microplastics and set a conservative threshold at one particle per sample, or 0.5 particles per liter. For Raman, <a target=\"_blank\" rel=\"noindex nofollow\" href=\"https:\/\/pmc.ncbi.nlm.nih.gov\/articles\/PMC13424059\">automated Raman workflows validated to 500 nm<\/a> require demonstrated recovery rates and particle-counting performance under actual operating conditions. Spectral identifiability alone does not suffice. The validated detection range for SWB-MP2-rev1 (Raman) begins at 20 \u00b5m. For SWB-MP1-rev1 (infrared), it begins at 50 \u00b5m. Any value below those floors falls outside the validated range for the California methods.<\/p>\n<\/li>\n<li>\n<p><strong>Spectral library validation for weathered particles.<\/strong> Environmental and product-matrix microplastics are often weathered by sunlight, heat, or mechanical stress, so their spectra differ from pristine reference materials. Spectral library matching must reach confidence above 75% against reference spectra before a polymer identification becomes reportable. <a target=\"_blank\" rel=\"noindex nofollow\" href=\"https:\/\/pmc.ncbi.nlm.nih.gov\/articles\/PMC12930080\">Pereira et al. (2026)<\/a> observed visible changes such as color loss in PP and LDPE and increased opacity in polyamide, even when FTIR spectra remained unchanged. These changes create a risk of misidentification during visual counting of weathered particles. Visual identification alone never suffices. Chemically confirmed identification is required for every counted particle or for an approved, statistically valid subsample.<\/p>\n<\/li>\n<li>\n<p><strong>Interlaboratory reproducibility checks.<\/strong> A method validated in one laboratory must show similar performance in other laboratories. A 2025 interlaboratory comparison under the <a target=\"_blank\" rel=\"noindex nofollow\" href=\"https:\/\/iris.inrim.it\/handle\/11696\/88180\">VAMAS prestandardization platform across 84 laboratories<\/a> showed that reproducibility for spectroscopic methods remains strongly method-dependent. The <a target=\"_blank\" rel=\"noindex nofollow\" href=\"https:\/\/publications.jrc.ec.europa.eu\/repository\/handle\/JRC146755\">JRC Erasmus Maris interlaboratory comparison<\/a> achieved mean recoveries of about 83% with precision around 18% across sea-water and river-water matrices, which the JRC described as satisfactory for those matrices. Brands should confirm that their chosen laboratory has participated in, or can show equivalent data to, an interlaboratory comparison for the specific method and matrix.<\/p>\n<\/li>\n<\/ol>\n<h2>How Validation Parameters Map to WQI-CS-01 Review<\/h2>\n<p>The Wellness Quality Institute review standard, WQI-CS-01, evaluates each validation parameter against defined criteria. The table below shows how the protocol steps above align with what The Wellness Quality Institute reviews during a Plastic-Free Pathway Verification.<\/p>\n<table style=\"min-width: 75px\">\n<colgroup>\n<col style=\"min-width: 25px\">\n<col style=\"min-width: 25px\">\n<col style=\"min-width: 25px\"><\/colgroup>\n<tbody>\n<tr>\n<th colspan=\"1\" rowspan=\"1\">\n<p>Validation Parameter<\/p>\n<\/th>\n<th colspan=\"1\" rowspan=\"1\">\n<p>WQI-CS-01 Review Element<\/p>\n<\/th>\n<th colspan=\"1\" rowspan=\"1\">\n<p>Acceptance Threshold Under Review<\/p>\n<\/th>\n<\/tr>\n<tr>\n<td colspan=\"1\" rowspan=\"1\">\n<p>Spiking recovery (PE, PP, PS)<\/p>\n<\/td>\n<td colspan=\"1\" rowspan=\"1\">\n<p>Spike recovery documentation reviewed against the acceptance window<\/p>\n<\/td>\n<td colspan=\"1\" rowspan=\"1\">\n<p>70\u2013130%; 90% or higher preferred for anchor polymers in water matrices<\/p>\n<\/td>\n<\/tr>\n<tr>\n<td colspan=\"1\" rowspan=\"1\">\n<p>Precision (RSD across replicates)<\/p>\n<\/td>\n<td colspan=\"1\" rowspan=\"1\">\n<p>Replicate data reviewed for consistency<\/p>\n<\/td>\n<td colspan=\"1\" rowspan=\"1\">\n<p>20% RSD or lower<\/p>\n<\/td>\n<\/tr>\n<tr>\n<td colspan=\"1\" rowspan=\"1\">\n<p>Blank correction (field, procedural, air)<\/p>\n<\/td>\n<td colspan=\"1\" rowspan=\"1\">\n<p>Blank data required; raw and corrected counts both reviewed<\/p>\n<\/td>\n<td colspan=\"1\" rowspan=\"1\">\n<p>All three blank types documented; blank-corrected counts reported by polymer and size fraction<\/p>\n<\/td>\n<\/tr>\n<tr>\n<td colspan=\"1\" rowspan=\"1\">\n<p>LOD\/LOQ, Raman<\/p>\n<\/td>\n<td colspan=\"1\" rowspan=\"1\">\n<p>Reporting limits reviewed against SWB-MP2-rev1 validated range<\/p>\n<\/td>\n<td colspan=\"1\" rowspan=\"1\">\n<p>Empirically established; must meet or exceed the lower bound above 20 \u00b5m<\/p>\n<\/td>\n<\/tr>\n<tr>\n<td colspan=\"1\" rowspan=\"1\">\n<p>LOD\/LOQ, FTIR<\/p>\n<\/td>\n<td colspan=\"1\" rowspan=\"1\">\n<p>Reporting limits reviewed against SWB-MP1-rev1 validated range<\/p>\n<\/td>\n<td colspan=\"1\" rowspan=\"1\">\n<p>Empirically established; must meet or exceed the lower bound above 50 \u00b5m<\/p>\n<\/td>\n<\/tr>\n<tr>\n<td colspan=\"1\" rowspan=\"1\">\n<p>Spectral library match<\/p>\n<\/td>\n<td colspan=\"1\" rowspan=\"1\">\n<p>Polymer identification confidence reviewed<\/p>\n<\/td>\n<td colspan=\"1\" rowspan=\"1\">\n<p>More than 75% confidence against reference spectra; visual identification alone is not accepted<\/p>\n<\/td>\n<\/tr>\n<tr>\n<td colspan=\"1\" rowspan=\"1\">\n<p>Polymer panel coverage<\/p>\n<\/td>\n<td colspan=\"1\" rowspan=\"1\">\n<p>Minimum panel reviewed: PE, PP, PET, PS, PVC, PA, PC, PMMA<\/p>\n<\/td>\n<td colspan=\"1\" rowspan=\"1\">\n<p>All anchor polymers (PE, PS, PVC, PET) required; unidentified particles reported separately<\/p>\n<\/td>\n<\/tr>\n<tr>\n<td colspan=\"1\" rowspan=\"1\">\n<p>Interlaboratory reproducibility<\/p>\n<\/td>\n<td colspan=\"1\" rowspan=\"1\">\n<p>Laboratory qualification tier reviewed (ELAP preferred; ISO\/IEC 17025 accepted)<\/p>\n<\/td>\n<td colspan=\"1\" rowspan=\"1\">\n<p>Accreditation must cover the specific method and matrix in scope<\/p>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>A Standard Met outcome under WQI-CS-01 requires two conditions together. The dataset must satisfy all applicable technical and data-quality requirements. It must also show no reportable target polymer particles within the tested particle-size range and approved reporting limits. A non-detect result alone does not suffice, because the reporting limits themselves must meet The Wellness Quality Institute requirements before the non-detect carries evidentiary weight.<\/p>\n<p><a target=\"_blank\" rel=\"noopener noreferrer nofollow\" href=\"https:\/\/www.wellnessqualityinstitute.com\">Turn real lab data into a claim you can support. Talk to The Wellness Quality Institute about Plastic-Free Pathway Verification.<\/a><\/p>\n<h2>Scope Lock and Boundaries for Claim Language<\/h2>\n<p>Validation of a single method on a single product lot supports claims only about that specific lot. It does not authorize claims about an entire product line, a brand, or future production. WQI-CS-01 enforces scope lock, which means every verification decision is tied to the specific product, SKU, matrix, production or sampling period, analytical method, tested particle-size range, polymer panel, and reporting limits that were reviewed. No company-wide or product-line claim can extend from a single dataset.<\/p>\n<p>Scope lock protects brands from accidental greenwashing by blocking scope extension. Scope extension occurs when a result from one lot, one method, or one size range is presented as a statement about everything the brand makes. Scope-locked claim language prevents that extension explicitly. Approved claim language under WQI-CS-01 connects to the Verification Scope record, which appears in The Wellness Quality Institute registry with a unique registry ID. Every public claim must link to that record so any buyer, retailer, or journalist can see exactly what was reviewed.<\/p>\n<p>The validated detection range also defines the claim boundary. SWB-MP2-rev1 (Raman) is validated for particles larger than 20 \u00b5m through 5,000 \u00b5m. SWB-MP1-rev1 (infrared) is validated for particles larger than 50 \u00b5m through 5,000 \u00b5m. The California definition of microplastics reaches down to 1 nanometer. The gap between what the definition covers and what any validated method can currently detect is thousands of times larger than the particles the methods can see. A &#8220;none detected&#8221; result is always bounded by the method floor. It means none found above that floor, using that method, on that lot. Claim language must reflect that boundary.<\/p>\n<p><em>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.<\/em><\/p>\n<h2>Frequently Asked Questions<\/h2>\n<h3>Target Recovery Rates for PE, PP, and PS in Water<\/h3>\n<p>The broadly accepted target window for spiking recovery in microplastics analysis is 70\u2013130%, with values at or above 90% preferred for anchor polymers such as polyethylene, polypropylene, and polystyrene in water matrices. Recovery below 70% indicates particle loss during extraction, density separation, or filtration steps that must be investigated and corrected before results are reportable. Recovery above 130% usually signals contamination or a measurement error. Precision across replicates, expressed as relative standard deviation, should not exceed 20%. Recovery is both polymer-specific and matrix-specific, so an extraction protocol that achieves more than 90% for PP may perform poorly for denser polymers like PET unless a higher-density separation medium is used.<\/p>\n<h3>How Laboratories Determine LOD and LOQ for Raman and FTIR<\/h3>\n<p>Limits of detection and quantification must be set with real data for each method and matrix. The limit of detection is the smallest amount a method can reliably detect. The limit of quantification is the smallest amount it can reliably measure. For \u00b5-FTIR workflows, laboratories typically derive LOD from procedural blank statistics. If blanks contain zero microplastics, a conservative LOD of one particle per sample is defensible. For Raman methods, LOD and LOQ must be established through demonstrated recovery rates and particle-counting performance under actual operating conditions, because spectral identifiability alone does not suffice. The California-validated detection range for Raman (SWB-MP2-rev1) begins at 20 \u00b5m. For infrared (SWB-MP1-rev1), it begins at 50 \u00b5m. Any result reported below those floors lies outside the validated range of either method and cannot support a defensible claim.<\/p>\n<h3>Required Blank Types and How to Apply Blank Correction<\/h3>\n<p>Three blank types are required in a defensible microplastics workflow. Field blanks detect contamination introduced during sample collection. Procedural blanks identify contamination introduced during laboratory processing steps such as digestion, filtration, and transfers. Air blanks, typically open containers of filtered water exposed during analysis, monitor airborne fiber deposition in the laboratory environment. All three must run with every sample batch. Results must report both raw particle counts and blank-corrected counts, along with the mean and standard deviation of particles detected in blanks, by polymer type and size fraction. A clear statement on whether blank correction was applied is required. Sample-preparation uncertainty often exceeds instrumental uncertainty in trace-level microplastics work, so rigorous blank management is a prerequisite rather than an optional quality step.<\/p>\n<h3>Interlaboratory Reproducibility and Transferability of Results<\/h3>\n<p>Interlaboratory reproducibility describes how consistently a method produces the same result when different laboratories test the same sample. In microplastics testing, reproducibility remains wide and method-dependent. A 2025 interlaboratory comparison across 84 laboratories showed that reproducibility for spectroscopic methods varies significantly across sites. For a dataset to support independent third-party review, the laboratory must show accreditation that covers the specific method and matrix, and ideally participation in a recognized interlaboratory comparison or proficiency-testing program. The Wellness Quality Institute preferred laboratory qualification is California ELAP accreditation for the applicable SWB microplastics method. ISO\/IEC 17025 accreditation with the method and matrix explicitly listed in the accredited scope is also accepted. Confirming laboratory qualification before commissioning testing avoids the costly outcome of generating a dataset that cannot support a verification review.<\/p>\n<h2>Next Steps for Brands That Already Have Lab Data<\/h2>\n<p>Many United States brands already hold laboratory data on microplastic content. That data only supports a defensible claim when it comes from a validated method, with documented recovery rates, appropriate blanks, empirically established reporting limits, and a qualified laboratory.<\/p>\n<p>The validation pathway follows a clear sequence.<\/p>\n<ol>\n<li>\n<p>Confirm laboratory qualification against The Wellness Quality Institute accreditation tiers before commissioning testing, which prevents the costly outcome of generating data from an unqualified source that cannot support verification.<\/p>\n<\/li>\n<li>\n<p>After confirming laboratory qualification, review the dataset against the core validation parameters, including spiking recovery of 70\u2013130% with 90% or higher preferred for anchor polymers, precision at or below 20% relative standard deviation, documented field, procedural, and air blanks, empirically established detection and quantification limits for the method and matrix, and spectral library confidence above 75% for each identified polymer. This review highlights any technical gaps before submission.<\/p>\n<\/li>\n<li>\n<p>Once technical parameters are confirmed, verify that the polymer panel covers at minimum PE, PP, PET, PS, PVC, PA, PC, and PMMA, with unidentified particles reported separately. Panel completeness is a prerequisite for submission.<\/p>\n<\/li>\n<li>\n<p>With qualification, parameters, and panel confirmed, submit the dataset, method documentation, product scope, and supporting controls to The Wellness Quality Institute for review against WQI-CS-01.<\/p>\n<\/li>\n<li>\n<p>Receive a verification decision of Standard Met or Standard Not Met, with approved claim language tied to the specific reviewed scope, or a private outcome with guidance on what the data does and does not support.<\/p>\n<\/li>\n<\/ol>\n<p>A Standard Not Met outcome remains private. It carries no public claim, no logo rights, and no registry listing. It is never described as a failed product, because it often reflects the testing rather than the product, and the company may resubmit with corrected or additional information.<\/p>\n<p>The verification period is 24 months from the sampling date of the most recent accepted dataset. Re-verification uses current production data, which reflects real lot-to-lot variability and ensures the mark remains accurate when a customer checks it.<\/p>\n<p><a target=\"_blank\" rel=\"noopener noreferrer nofollow\" href=\"https:\/\/www.wellnessqualityinstitute.com\">Turn real lab data into a claim you can support. Talk to The Wellness Quality Institute about Plastic-Free Pathway Verification.<\/a><\/p><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Learn how The Wellness Quality Institute validates microplastics testing methods for defensible, audit-ready claims. Explore WQI-CS-01 criteria today.<\/p>\n","protected":false},"author":117,"featured_media":59,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"inline_featured_image":false,"footnotes":""},"categories":[6],"tags":[],"class_list":["post-60","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-reports"],"_links":{"self":[{"href":"https:\/\/www.wellnessqualityinstitute.com\/articles\/wp-json\/wp\/v2\/posts\/60","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.wellnessqualityinstitute.com\/articles\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.wellnessqualityinstitute.com\/articles\/wp-json\/wp\/v2\/types\/post"}],"replies":[{"embeddable":true,"href":"https:\/\/www.wellnessqualityinstitute.com\/articles\/wp-json\/wp\/v2\/comments?post=60"}],"version-history":[{"count":1,"href":"https:\/\/www.wellnessqualityinstitute.com\/articles\/wp-json\/wp\/v2\/posts\/60\/revisions"}],"predecessor-version":[{"id":130,"href":"https:\/\/www.wellnessqualityinstitute.com\/articles\/wp-json\/wp\/v2\/posts\/60\/revisions\/130"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.wellnessqualityinstitute.com\/articles\/wp-json\/wp\/v2\/media\/59"}],"wp:attachment":[{"href":"https:\/\/www.wellnessqualityinstitute.com\/articles\/wp-json\/wp\/v2\/media?parent=60"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.wellnessqualityinstitute.com\/articles\/wp-json\/wp\/v2\/categories?post=60"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.wellnessqualityinstitute.com\/articles\/wp-json\/wp\/v2\/tags?post=60"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}