Phosphatidylserine Particle Size Distribution Review for US and EU Buyers

A quality team sourcing bulk phosphatidylserine (PS) usually meets particle size distribution when a specification arrives without a particle row, or when a capsule trial behaves differently from the sample. The direct answer: particle size distribution is a quality and application-fit parameter, not a regulated maximum in the US or EU for PS, so the buyer's job is to confirm the test method, read the D-values and retained fractions on the specification or COA, agree measurable ranges for the exact grade and format, and verify batch-to-batch consistency before approving the first bulk order.

This review is written for importers, distributors, supplement manufacturers, and quality teams in North America and Europe. It explains what D10/D50/D90 mean, how laser diffraction and analytical sieving differ, what a PSD row should contain, and where the US and EU regulatory context fits. This is a specification and quality-control discussion, not a medical discussion.

Where Nutranexa is mentioned, only verified public facts are used. Nutranexa identifies itself as Shandong Baianrui Biopharmaceutical Co., Ltd., founded in 2013, operating a 110,000+ m2 campus, and primarily serving export markets in Europe and North America. Its public PS pages list soy PS and sunflower PS, the PS specification matrix shows assay, moisture, peroxide value, acetone insolubles, bulk density, and shelf life, and particle specifications are confirmed with the sales team for the quoted grade. Its published minimum order is 25 kg with 25 kg net per drum, and sample COA evidence with a QB/T 5821-2023 test basis is shown on the Quality & R&D page.

The Direct Answer Buyers Need First

Run this five-point map before approving a PS specification or accepting a batch:

What Particle Size Distribution Means: D10, D50, and D90

Particle size distribution describes the population of particles in a powder, not a single number. The spread of sizes affects handling, filling, blending, and appearance.

The common summary values are percentiles read from the cumulative distribution:

• D10. The size below which 10% of the distribution falls. It is a practical proxy for the finest particles in the powder.
• D50. The median particle size. Half of the distribution is below this value and half is above it. It is the number buyers usually quote first.
• D90. The size below which 90% of the distribution falls. It describes the coarser end of the powder and matters for feeding, dust, and blend interactions.

The spread between these points is summarized as span, calculated as (D90 - D10) / D50. A narrow span means a more uniform population; a wide span means fines and coarse particles coexist. ISO 9276-1 sets the standard rules for representing particle size data.

For PS powder, D50 shows the typical particle, while D10 and D90 reveal dustiness, flow, and segregation tendency. All three belong in a review, not just the median.

Why PSD Matters for PS Applications

Particle size does not predict every handling property, but it is a primary driver of several outcomes that buyers care about:

Capsule and tablet manufacturers often care most. Research on capsule filling has shown that particle size influences fill-weight uniformity and that the workable compression range changes with particle size. The takeaway is not that one particle size is universally correct, but that the powder must match the formulation, equipment, and target dose.

Particle size also interacts with other parameters: moisture changes cohesion, bulk density changes how much powder fits a fill volume, and shape and surface affect flow. That is why a PSD review belongs next to the moisture and water activity review and the flowability and blend-uniformity pilot guide rather than replacing them.

How PSD Is Measured: Laser Diffraction vs Analytical Sieving

Two methods dominate ingredient specifications, and they answer different questions:

Laser diffraction measures the angular scattering pattern of dispersed particles and converts it into a size distribution. USP <429>, Ph. Eur. 2.9.31, and ISO 13320 describe the harmonized approach and instrument qualification. Because results depend on dispersion and refractive-index settings, the method details must travel with the data.

Analytical sieving separates powder on a stack of calibrated sieves and reports the mass retained on each screen. USP <786> and Ph. Eur. 2.9.38 describe the procedure, noting that it is generally intended for powders where at least 80% of particles are larger than 75 µm. For a fine ingredient such as PS powder, a pure sieve result can miss the fine end of the distribution, which is why suppliers often report laser diffraction data instead.

The key rule: never compare a laser-diffraction D50 with a sieve-based fraction as if they were the same measurement. Ask which method generated the data and keep the same method for incoming checks and batch-to-batch monitoring. The third-party testing review explains when an independent laboratory should repeat the measurement.

How to Read a PSD Report or COA Row

When a supplier provides particle size data, check:

• Method named. Laser diffraction, analytical sieving, or another defined method, with the chapter or standard.
• Dispersion and measurement conditions. Laser results depend on dispersion and instrument settings.
• Units. D-values in micrometers (µm); fractions as percentages.
• Percentiles reported. D10, D50, and D90, or at least D50 plus one width measure.
• Distribution context. Fines percentage, retained fraction on a named sieve, or span.
• Batch linkage. Batch number and report date should match the COA.
• Limit versus result. A specification limit is different from a batch result.

Many published PS COAs do not include a particle size row. That is common for lecithin-derived powders, where routine release testing centers on assay, moisture, peroxide value, and microbiology. The gap is a decision point, not an automatic failure: the buyer asks whether particle size is controlled and documented for the quoted grade, and whether data can be supplied when the application needs it.

Nutranexa's public PS specification matrix is a useful example: it lists assay, moisture, peroxide value, acetone insolubles, bulk density, and shelf life, while particle specifications are confirmed with the sales team for the quoted grade, and the published sample COAs show batch results on a QB/T 5821-2023 basis without a particle-size row. The correct next step is a direct request for the current specification and any PSD data or method statement. The general workflow for reading a PS certificate is covered in the COA and specification review.

US Regulatory Context: A Quality Attribute, Not a Fixed Limit

In the United States, there is no FDA maximum or minimum particle size for phosphatidylserine as a dietary ingredient. Particle size is a quality attribute the manufacturer defines, controls, and verifies:

• Dietary supplement GMP. Under 21 CFR Part 111, manufacturers must establish specifications for components and finished products, including identity, purity, strength, and composition, and verify they are met.
• Blend uniformity practice. FDA's guidance on powder blends recommends stratified in-process sampling and points to particle size and shape as factors that can affect mixture stability and segregation.
• Nanotechnology screening. FDA's 2014 guidance asks manufacturers to consider whether a material has at least one dimension in the nanoscale range (approximately 1 to 100 nm) or exhibits dimension-dependent properties. A conventional micron-scale PS powder does not raise this question; a deliberately engineered "nano PS" would.

The US review is therefore specification-based: confirm the supplier defines particle size in the specification or quality agreement, verify data on incoming lots, and keep the incoming inspection and warehouse release procedure aligned with the agreed method.

EU Regulatory Context: No PS Limit, but Nanoscale Is a Different Question

In the European Union, there is also no harmonized maximum or minimum particle size for phosphatidylserine. PS is an ingredient rather than a food additive with an EU specification, so particle size is an agreed quality parameter under general food law and contract.

The regulatory question that particle size can trigger in the EU is the nanomaterial one:

• Definition. Commission Recommendation 2011/696/EU defines a nanomaterial as a material in which 50% or more of the particles in the number size distribution have one or more external dimensions in the range 1 to 100 nm.
• Novel food trigger. Under Regulation (EU) 2015/2283, food consisting of, isolated from, or produced from engineered nanomaterials is a novel food category, so a deliberately engineered nanoscale PS would need an authorization pathway, not just a specification row.
• Labeling. Regulation (EU) 1169/2011 requires ingredients that are engineered nanomaterials to be indicated in the list of ingredients.
• Risk assessment guidance. EFSA's 2021 guidance describes the agency's assessment of nanomaterials in the food and feed chain.

The practical point: a conventional lecithin-derived PS powder with micron-scale particles sits outside the nanomaterial framework, and no EU rule sets a specific PSD limit for it. The review should still ask whether the quoted product is intentionally manufactured at nanoscale. If yes, EU buyers face novel food and labeling obligations, and US buyers face the FDA screening question. For everything else, the EU review is a document and specification review, the same as in the US.

Where PSD Fits in Supplier Qualification

Particle size belongs in the same qualification file as other parameters:

The supplier onboarding and supplier quality agreement workflows are where PSD criteria should be recorded in writing, and the documents for PS ingredients checklist shows the full document set to hold.

Supplier Questions and Acceptance Criteria

Add these questions to your supplier questionnaire:

1. Does the quoted grade have a defined particle size specification? If yes, provide the method, D-values, and limits.
2. Which method generated the data: laser diffraction or analytical sieving? Which chapter or standard was followed?
3. Can you provide PSD data for the current batch, and does it match the evaluated sample?
4. What routine control keeps particle consistency, and what triggers a recheck (new source, milling, process change)?
5. Is the product intentionally manufactured at nanoscale? If yes, what regulatory position applies?
6. Will the COA or a supporting report include the agreed PSD row or method statement on request?
7. What is the agreed acceptance range for D10, D50, and D90, including the fines fraction?

For acceptance criteria, agree on something measurable: for example, a D50 range in micrometers with a named method and dispersion condition, plus a maximum fines fraction where dust or segregation matters. Set the range for your formula and equipment, then confirm it with actual batch data.

Need current PS specifications, COA samples, and particle data or method statements for your PSD review? Request the specification and document evidence with your source preference, target assay, application, and destination market.

Conclusion

Particle size distribution is one of the most practical physical specifications a PS buyer can review, and easy to get wrong when numbers from different methods are compared. Confirm the method, read D10/D50/D90 with units, agree measurable acceptance ranges for the exact grade and format, and tie every result to a named batch. In both the US and the EU, particle size is a quality attribute rather than a regulated limit, so the decision framework belongs to buyer and supplier together; the only regulatory trigger on the checklist is deliberate nanoscale engineering. A properly checked PSD row turns a powder specification into an evidence-backed approval decision.

FAQ

Does particle size matter for phosphatidylserine powder?

Yes, for application fit and process consistency. Particle size distribution influences capsule fill-weight uniformity, tablet feeding, blend segregation, dustiness, and handling, so buyers should confirm the method and D-values for the exact grade and format.

What is D50 on a particle size report?

D50 is the median particle size: 50% of the distribution is below this value and 50% is above it, read from the cumulative distribution. It is usually reported with D10 and D90, which describe the fine and coarse ends of the powder.

Should I ask for laser diffraction or sieve analysis for PS powder?

Ask for the method that matches the supplier's specification and your incoming-control plan, and keep it consistent. Laser diffraction (USP <429>, Ph. Eur. 2.9.31, ISO 13320) gives a full volume-based distribution, while analytical sieving (USP <786>, Ph. Eur. 2.9.38) reports mass retained on screens and suits coarser powders.

Do US or EU regulations set a particle size limit for phosphatidylserine?

No. Neither FDA nor the EU sets a maximum or minimum particle size for PS as an ingredient. Particle size is a quality attribute defined and verified by the manufacturer, which is why buyers agree measurable acceptance ranges in the specification or quality agreement.

Can particle size differences between batches affect my capsules or tablets?

Yes. Research on capsule filling has shown that particle size influences fill-weight uniformity and the workable compression range. If D50 or the fines fraction shifts between batches, filling behavior and blend uniformity can change even when assay stays the same.

What should I request from a PS supplier for a PSD review?

Request the grade-specific specification with a named method, D10/D50/D90 values with units, PSD data for the current batch and sample, a statement on routine control, and whether the product is intentionally manufactured at nanoscale.

Sources

• USP-NF <786> Particle Size Distribution Estimation by Analytical Sieving
• USP-NF <429> Light Diffraction Measurement of Particle Size
• EDQM: Ph. Eur. 2.9.31 Particle Size Analysis by Laser Light Diffraction
• EDQM: Ph. Eur. 2.9.38 Particle-Size Distribution Estimation by Analytical Sieving
• ISO 13320:2020 Particle Size Analysis - Laser Diffraction Methods
• ISO 9276-1 Representation of Results of Particle Size Analysis - Graphical Representation
• Federal Register: FDA Draft Guidance on Powder Blends and Finished Dosage Units - Stratified In-Process Dosage Unit Sampling and Assessment (2003)
• Federal Register: FDA Guidance on Considering Whether an FDA-Regulated Product Involves the Application of Nanotechnology (2014)
• eCFR: 21 CFR 111.70 - Requirements for Establishing and Maintaining Specifications
• EFSA: Guidance on Risk Assessment of Nanomaterials to be Applied in the Food and Feed Chain (EFSA Journal 2021;19(8):6768)
• EUR-Lex: Regulation (EU) 2015/2283 on Novel Foods
• EUR-Lex: Commission Recommendation 2011/696/EU on the Definition of Nanomaterial
• EUR-Lex: Regulation (EU) 1169/2011 on the Provision of Food Information to Consumers

Recommended next steps

• Review the Phosphatidylserine product page.
• Compare Soy PS and Sunflower PS.
• Check manufacturing proof and Quality & R&D.