Unknown Particle in an Injectable? Here’s How to Investigate It

Finding an unknown visible particle or fiber in an injectable pharmaceutical product can trigger an important quality investigation.

The immediate question may be simple:

“What is this particle?”

But a useful investigation needs to go further.

The investigation should seek to understand what the particle is, what it is made of, what its morphology looks like, whether it resembles known product-contact or non-contact materials, and what potential contamination source should be investigated.

This is where pharmaceutical particle characterization becomes valuable.

Instead of relying on visual appearance alone, analytical techniques such as microscopy, Scanning Electron Microscopy with Energy Dispersive X-ray Spectroscopy (SEM-EDS), Fourier Transform Infrared Spectroscopy (FTIR), and thermal analysis can generate complementary information about an unknown contaminant.

Confianca Pharmazon’s particle-characterization approach combines these techniques with a reference library of product-contact and non-contact components. Its material describes an optional Gemba activity to identify relevant components, collection of material coupons, and analysis using SEM-EDS, FTIR, TGA/STA and microscopy. Confianca-Particle-Characteriza…

This article explains how that workflow can support an unknown particle analysis pharmaceutical investigation, from particle recovery through analytical characterization and potential source comparison.

Why Unknown Particles in Injectable Products Require Investigation

Injectable products demand a high level of control because they bypass many of the body’s natural protective barriers.

A visible particle can potentially originate from numerous materials encountered throughout manufacturing, filling, inspection, packaging or handling.

Potential candidates can include:

• glass;
• metal;
• polymer or elastomer;
• fibers;
• filter material;
• garment-related fibers;
• packaging components;
• equipment or product-contact components;
• process-related residues; or
• other environmental or extrinsic materials.

This is also why appearance alone is generally insufficient for source identification.

A black particle, for example, is not automatically a particular polymer or machine component. A transparent fragment should not automatically be assumed to be glass.

The investigation needs analytical evidence.

Confianca’s visual-inspection program reflects this broader source-based approach: its defect materials can use real sources including primary packaging material, machine/product-contact materials, filters and garments. Its documentation also specifically covers intrinsic and extrinsic materials and their probable sources during visual-inspection training.

The Core Principle: Identify the Particle, Then Investigate the Source

A strong particle investigation can be thought of as a chain:

Detection → Recovery → Documentation → Microscopy → SEM-EDS → FTIR → Complementary Analysis → Reference Library Comparison → Potential Source Identification → Root-Cause Investigation

The important distinction is that particle identification and root-cause determination are not necessarily the same thing.

An analytical laboratory may determine that a particle is consistent with a particular material or elemental composition. The manufacturing investigation must then establish how that material could have entered the product.

That distinction prevents an analytical match from being treated automatically as proof of root cause.

Step 1: Document the Particle Before Recovery

Before extensive manipulation, document the observation.

Record relevant information such as the sample or batch identification, container type, product/formulation, inspection stage, approximate particle location, apparent color, shape, size and mobility, and the circumstances under which it was detected.

Where practical, capture images.

The objective is to preserve the particle’s original context.

This becomes particularly useful later if the analytical results suggest a material associated with a specific process component.

Step 2: Recover the Unknown Particle Carefully

The particle must then be recovered in a manner suitable for analysis.

This step is more important than it may initially appear.

Poor handling can introduce additional material or alter the specimen, complicating interpretation. The recovery approach therefore needs to be appropriate for the product, container and planned analytical techniques.

Confianca’s own workflow explicitly places particle recovery before SEM-EDS analysis when investigating an unknown particle or fiber. Confianca-Particle-Characteriza…

Once recovered, the specimen can move into progressively more detailed characterization.

Step 3: Start With Microscopic Analysis

What can microscopy tell us?

Microscopy provides the first detailed view of the particle’s physical characteristics.

Depending on the specimen, an analyst may evaluate features such as:

Morphology → irregular, spherical, elongated, flaky, crystalline or fibrous
Surface → smooth, rough, fractured, layered or textured
Color → transparent, translucent, white, black or colored
Geometry → fiber, shard, film, flake or fragment
Dimensions → approximate particle or fiber size

Confianca’s particle-characterization documentation describes microscopy as a technique for detecting microscopic contaminants on transparent surfaces such as filters and slides and for enhancing the visibility of organic and biological particles. Confianca-Particle-Characteriza…

Microscopy therefore provides an important first classification.

But morphology alone often cannot establish composition.

A dark fragment could have multiple origins. A clear fragment could resemble several different materials.

That is where SEM-EDS becomes especially useful.

Step 4: SEM-EDS — Examine Morphology and Elemental Composition

What is SEM-EDS?

SEM stands for Scanning Electron Microscopy.

EDS stands for Energy Dispersive X-ray Spectroscopy.

Used together, they provide two complementary types of information:

SEM → What does the particle’s surface and morphology look like at high magnification?

EDS → Which detectable elements are present in the analyzed region?

According to Confianca’s particle-characterization documentation, its SEM-EDS capability provides high-resolution imaging at micro- and nanoscale levels alongside elemental detection. The described system includes SE, BSE, UVD and STEM detectors and uses EDS for elemental-composition analysis. Confianca-Particle-Characteriza…

This combination makes SEM-EDS particularly useful during a foreign particle analysis pharmaceutical investigation.

Example: Suspected Metallic Particle

Imagine that a small grey particle is recovered from an injectable vial.

Under microscopy, it appears:

irregular, opaque and reflective.

SEM may reveal characteristic surface features.

EDS can then provide information about the elemental composition of the analyzed area.

The investigation team can compare those findings against relevant materials used within the manufacturing process.

That comparison could direct attention toward equipment surfaces, components, tools or other materials containing similar elemental constituents.

But an elemental similarity should be treated as evidence supporting a hypothesis, not automatic proof of origin.

Process history and additional investigation remain necessary.

Step 5: Use FTIR to Investigate Molecular Composition

SEM-EDS is powerful, but it does not answer every material-identification question.

For many organic materials and polymers, FTIR can provide complementary molecular information.

FTIR stands for Fourier Transform Infrared Spectroscopy.

Instead of focusing primarily on elemental composition, FTIR examines infrared absorption associated with molecular bonding and functional groups.

That makes it particularly valuable when investigating materials such as:

• polymers;
• elastomeric materials;
• films;
• organic residues;
• certain fibers;
• coatings; and
• other suitable organic or solid-state materials.

Confianca’s documentation describes its FTIR system as suitable for qualitative and quantitative characterization of molecular structures and for analysis of powders, thin films, polymers, ceramics, liquids and other solid-state materials. Confianca-Particle-Characteriza…

SEM-EDS vs FTIR: Why Both Can Matter

The two techniques answer different questions.

This is why an investigation should not necessarily begin with the question:

“Should we use SEM or FTIR?”

A better question is:

“What analytical information do we need to identify this particular particle?”

Sometimes microscopy plus SEM-EDS may provide sufficient discriminatory information.

In another investigation, FTIR may be essential.

For more complex materials, several techniques may need to be interpreted together.

Step 6: Add TGA/STA When Complementary Thermal Information Is Useful

Confianca’s analytical workflow also includes TGA/STA.

Its documentation describes a simultaneous thermal analyzer combining Thermogravimetric Analysis (TGA) and Differential Thermal Analysis (DTA), with DSC conversion capability. The technique studies weight changes and thermal events as a function of temperature and time and can be applied to materials including polymers, composites, nanomaterials, metals, ceramics and inorganic materials. Confianca-Particle-Characteriza…

Thermal analysis can therefore add another layer of characterization when microscopy, elemental information and molecular spectroscopy need complementary evidence.

The result is not simply another test.

It is another independent material characteristic that can be compared against potential source materials.

Step 7: Build a Product-Contact Material Reference Library

This is one of the most important parts of a mature unknown particle investigation workflow.

Identifying the chemistry of a particle is useful.

But an investigation becomes significantly more actionable when the result can be compared against known materials actually present in the manufacturing environment.

That is the purpose of a contact-part and material reference library.

Confianca’s described approach begins with an optional Gemba exercise with the client to identify product-contact and non-contact parts. Coupons from those materials can then be collected and characterized using:

SEM-EDS + FTIR + TGA/STA + Microscopy. Confianca-Particle-Characteriza…

The resulting library can capture reference characteristics associated with known manufacturing materials.

Why a Reference Library Changes the Investigation

Consider two approaches.

Investigation without a reference library

An unknown particle is recovered.

SEM-EDS suggests a particular elemental profile.

The result provides useful characterization—but the team must still search through equipment, components and process materials to determine what could reasonably match it.

Investigation with a reference library

The unknown particle is recovered.

Microscopy documents its morphology.

SEM-EDS provides elemental information.

FTIR or thermal analysis provides complementary information where appropriate.

Those observations can then be compared with previously characterized materials from the facility.

Now the question becomes more focused:

“Which known process material has characteristics consistent with this unknown particle?”

That can make the subsequent root-cause investigation more targeted.

Confianca describes this principle directly: once its library has been prepared, morphology and bonding-structure data for product-contact components are available for comparison when an unknown particle or fiber is encountered. Confianca-Particle-Characteriza…

Step 8: Compare the Unknown Particle Against Potential Sources

The comparison should consider the combined analytical profile, rather than relying on a single observation.

For example:

Unknown Particle

Microscopy
↓
Black irregular fragment

SEM
↓
Specific surface morphology

EDS
↓
Characteristic elemental profile

FTIR
↓
Polymer/molecular signature, where applicable

Reference Library
↓
Potentially similar known material identified

Process Investigation
↓
Evaluate where, when and how that material could contact or enter the product

This is where analytical characterization begins to support source investigation.

Potential candidates might include product-contact parts, non-contact components, primary packaging, filters, garments or other process materials identified during the investigation.

Step 9: Correlate Analytical Results With Manufacturing Evidence

An analytical match alone should not close the investigation.

Suppose a recovered particle is analytically consistent with a particular polymer used somewhere on a filling line.

The next questions should examine the process context.

Was that material actually present on the relevant equipment?

Was it exposed to the product pathway?

Was there abnormal wear or damage?

Were maintenance activities performed?

Did the event coincide with equipment intervention or component replacement?

Are similar particles present elsewhere?

Does batch history support the proposed source?

Can the suspected component’s morphology and analytical profile reasonably explain the recovered particle?

This stage transforms material characterization into a broader root-cause investigation.

Step 10: Use the Findings to Support CAPA and Prevention

Once the evidence supports a probable source, the investigation can inform appropriate corrective and preventive actions.

Depending on the established root cause, actions might involve equipment or component inspection, replacement or maintenance; improvements to material controls; enhanced inspection; procedural changes; additional monitoring; personnel training; or expansion of the reference library.

The specific CAPA should follow from the actual investigation evidence rather than from the analytical result alone.

Where Visual Inspection and Knapp Kits Fit Into the Lifecycle

Particle characterization answers:

“What might this unknown particle be?”

Visual-inspection qualification addresses another important question:

“Can our inspection process reliably detect relevant particulate defects?”

These activities complement one another.

Confianca’s Visual Inspection Knapp Kit documentation includes particulate materials such as glass, metal, black and white particles, fibers and other customer-specified materials. It also describes certified particle/fiber sizing, qualification kits, defect libraries and training for manual and automatic visual inspection.

The documentation specifically notes that known-size particulate materials are used to train visual inspectors to identify particulate defects during routine inspection.

Confianca also describes manual visual-inspection kits for liquid and lyophilized formulations in vials, cartridges and prefilled syringes, as well as Knapp Kits for manual and automatic visual-inspection machines. Confianca-Pharmazon-Product-Cat…

This creates a useful quality lifecycle:

Detect → Characterize → Investigate Source → Correct → Train/Qualify → Monitor

Unknown Particle Investigation: Practical Decision Tree

A practical investigation can therefore follow this logic:

Unknown particle detected in injectable product
↓
Document the observation and preserve sample context
↓
Recover the particle appropriately
↓
Perform microscopy
↓
Evaluate morphology, dimensions, color and physical characteristics
↓
Select analytical characterization based on the specimen

For suspected inorganic/metallic material:

SEM → EDS → elemental profile

For suspected polymeric/organic material:

Microscopy → FTIR, with SEM-EDS where useful

For complex or ambiguous materials:

Microscopy + SEM-EDS + FTIR + TGA/STA as appropriate

↓
Compare results with known contact/non-contact material library
↓
Generate potential source hypothesis
↓
Correlate with manufacturing, maintenance and batch evidence
↓
Determine supported root cause
↓
Implement appropriate CAPA and prevention strategy

The exact analytical sequence should be selected according to the sample and investigation requirements rather than treated as a rigid one-size-fits-all testing panel.

Common Mistakes During Pharmaceutical Particle Investigations

One common mistake is identifying a particle solely by color or visual appearance. Another is relying on a single analytical technique when the material requires complementary evidence.

Equally important is not having reference samples from actual manufacturing components. Knowing that a particle appears polymeric, metallic or glass-like does not necessarily identify where it originated.

Finally, teams should avoid treating a laboratory similarity as definitive proof of root cause. Analytical characterization identifies and compares material properties; process investigation establishes the credible contamination pathway.

Particle Characterization Services at Confianca Pharmazon

Confianca Pharmazon states that it has developed a laboratory in Ahmedabad for Library Preparation & Particle Characterization Testing, with an integrated analytical approach using:

Microscopic Analysis → FTIR → SEM with EDS → TGA/STA. Confianca-Particle-Characteriza…

Its particle-characterization material specifically describes a workflow in which product-contact and non-contact components are identified, reference coupons are collected and analyzed, and recovered unknown particles or fibers can subsequently be characterized and compared to support source investigation. Confianca-Particle-Characteriza…

The broader Confianca portfolio also includes Visual Inspection Knapp Kits, manual visual-inspection solutions and automated qualification-related solutions. Confianca-Visual-Inspection-Kna…

This allows particle characterization to be considered alongside the wider lifecycle of particulate detection, visual-inspection qualification, contamination investigation and prevention.

Frequently Asked Questions

What is unknown particle analysis in pharmaceuticals?

Unknown particle analysis is the systematic characterization of a foreign or unexplained particle found in a pharmaceutical product or manufacturing environment. Techniques may include microscopy, SEM-EDS, FTIR and complementary thermal analysis, depending on the nature of the specimen.

What does SEM-EDS tell you about a pharmaceutical particle?

SEM provides high-resolution information about particle morphology and surface characteristics, while EDS provides elemental-composition information from the analyzed region. Together, these data can help classify an unknown contaminant and compare it with potential source materials. Confianca’s documented SEM-EDS setup combines surface-morphology analysis with elemental detection. Confianca-Particle-Characteriza…

When is FTIR useful for particle identification?

FTIR is particularly valuable when molecular or bonding information is required, including characterization of many polymers and organic materials. Confianca’s documented FTIR capability covers powders, thin films, polymers, ceramics, liquids and other solid-state materials. Confianca-Particle-Characteriza…

Can SEM-EDS identify the exact source of contamination?

SEM-EDS can provide strong evidence about morphology and elemental composition, but identifying an exact manufacturing source generally requires comparison with reference materials and correlation with process evidence.

Why create a contact-part library before a contamination event?

A reference library provides analytical profiles for known materials in the manufacturing environment. When an unknown particle is subsequently recovered, its characteristics can be compared with those reference materials, potentially narrowing the source investigation.

How are microscopy and SEM different?

Conventional microscopy is useful for initial observations such as size, color, morphology and fiber/particle characteristics. SEM provides substantially higher-resolution surface information and, when combined with EDS, adds elemental-composition data.

What happens after the particle is identified?

The analytical findings should be correlated with manufacturing records, equipment and component condition, maintenance history, process observations and other relevant evidence. This supports root-cause assessment and, where appropriate, CAPA.

From “Unknown Particle” to Evidence-Based Investigation

An unknown particle in an injectable product should not remain simply an unexplained visual defect.

A structured investigation can progressively transform the observation into analytical evidence:

Microscopy helps establish what the particle looks like.

SEM reveals detailed morphology.

EDS provides elemental information.

FTIR contributes molecular and bonding information.

TGA/STA can add thermal characterization.

And a contact-part/material reference library gives those results manufacturing context.

The strongest investigation is therefore not based on one instrument. It combines complementary analytical techniques with reference materials and process knowledge to move from:

“There is an unknown particle.”

to:

“Here is what the particle is analytically consistent with, here are the potential sources, and here is the manufacturing evidence needed to establish the root cause.”

For pharmaceutical manufacturers handling injectable products, that distinction can make particle investigations more systematic, traceable and scientifically defensible.

Need to characterize an unknown particle or fiber found in your pharmaceutical product? Confianca Pharmazon provides Particle Characterization and Contact-Part Library Preparation using SEM-EDS, FTIR, microscopy and TGA/STA to support contamination-source investigations. Contact our team to discuss your sample and investigation requirements.