Applications of Liquid Particle Counter in Pharma

Maintaining pharmaceutical product quality requires more than checking the appearance, composition and purity of a formulation. Particulate contamination is another important quality consideration, particularly in injectable and parenteral products where unwanted particles can affect product safety and quality.

Many particles present in pharmaceutical liquids are too small to be detected through visual inspection. These are commonly referred to as subvisible particles. Identifying and measuring them requires appropriate analytical testing methods and reliable laboratory instruments.

This is where a Liquid Particle Counter plays an important role in pharmaceutical quality control.

A liquid particle counter is an analytical instrument designed to measure the size and number of particles present in liquid samples. It helps pharmaceutical laboratories evaluate particulate matter and supports testing activities associated with injectable products, pharmaceutical formulations and other liquid samples.

In this guide, we will explore the applications of liquid particle counters in pharmaceuticals, their working principles, the importance of USP standards, key benefits and factors to consider when selecting a suitable instrument for your laboratory.

What Is a Liquid Particle Counter?

A liquid particle counter is a specialized analytical instrument used to detect, measure and count particles suspended in liquid samples.

In pharmaceutical laboratories, it is particularly relevant for measuring subvisible particulate matter in injectable preparations and other suitable pharmaceutical samples.

These instruments commonly use light obscuration technology, in which particles passing through a measurement zone interrupt a beam of light. The resulting changes in light intensity are processed to estimate particle size and count.

The instrument can help laboratory professionals understand:

The number of particles present in a liquid sample.
The size distribution of detected particles.
Whether particulate matter meets applicable testing requirements.
Potential contamination trends in liquid samples.

Unlike visual inspection, which is intended to identify visible particles, liquid particle counting provides quantitative information about particles within the instrument's validated measurement range.

Working Principle of a Liquid Particle Counter

Most pharmaceutical liquid particle counters based on light obscuration operate through a defined measurement process.

The general working process involves four stages:

1. Sample Introduction

A prepared liquid sample is introduced into the instrument through a suitable sample delivery system. The sample preparation and handling procedure must be appropriate for the formulation being tested.

2. Light Obscuration

The liquid passes through a measurement zone illuminated by a light source. When particles pass through this zone, they block or scatter a portion of the incident light.

3. Signal Detection

A detector measures the changes in light intensity caused by the passing particles. The instrument converts these signals into electrical measurements.

4. Particle Size and Count Analysis

The instrument processes the detected signals to estimate particle sizes and particle counts. Results can be presented as particle concentrations or counts within specified size ranges, depending on the instrument and method.

This technology provides quantitative particle measurement for suitable samples and supports pharmaceutical particulate matter testing.

Light Obscuration Technology

Light obscuration is an established technique used for subvisible particulate matter analysis.

Its basic principle is that particles passing through a defined light beam cause a reduction in transmitted light intensity. The magnitude of the change is related to the particle's optical properties and size.

The technology is particularly relevant to pharmaceutical testing under USP General Chapter 788, where light obscuration is an established method for measuring particulate matter in injections.

However, the suitability of this technique depends on sample characteristics. Certain formulations, including some protein solutions, emulsions and suspensions, may require alternative or complementary testing methods.

Understanding Particle Size and Particle Count

Two important parameters measured during liquid particle analysis are:

Particle size: The estimated diameter of individual particles detected by the instrument.
Particle count: The number of particles detected within defined size ranges in a measured sample volume.

For pharmaceutical testing, results may be expressed as particles per container or particles per millilitre, depending on the applicable method and sample requirements.

Understanding both parameters helps laboratories assess particulate contamination more effectively.

Why Is Liquid Particle Counting Important in Pharmaceuticals?

Pharmaceutical products must meet established quality requirements before they are released for distribution and use.

Particulate matter testing is particularly important for injectable preparations because these products are administered directly into the body. Unwanted particulate contamination therefore requires careful evaluation.

A liquid particle counter supports pharmaceutical laboratories by providing quantitative information about subvisible particles.

Identifying Subvisible Particulate Contamination

Not all particles in pharmaceutical liquids are visible during routine inspection.

Subvisible particles may originate from different sources, including:

Raw materials and formulation ingredients.
Manufacturing and processing equipment.
Packaging components and containers.
Environmental contamination.
Product handling and transfer operations.

Liquid particle counting helps identify and quantify particles within the instrument's measurement capabilities, supporting laboratory investigations into particulate contamination.

Supporting Pharmaceutical Product Quality

Particle measurement provides useful information for evaluating the particulate quality of pharmaceutical preparations.

It can support:

Routine quality control testing.
Product development and formulation studies.
Manufacturing process investigations.
Evaluation of particulate contamination trends.
Testing against applicable pharmacopoeial requirements.

Improving Laboratory Testing and Quality Control

Automated liquid particle counting can help standardize measurement workflows when the instrument and analytical method are suitable.

It provides quantitative results that can be documented, reviewed and compared as part of a laboratory's established quality management procedures.

It does not replace other required pharmaceutical quality tests, but it can serve as an important component of a comprehensive testing strategy.

Major Applications of Liquid Particle Counter in Pharmaceuticals

Liquid particle counters have several applications across pharmaceutical manufacturing, quality control and research laboratories. Their use depends on the formulation, testing objective, applicable pharmacopoeial requirements and suitability of the measurement technique.

Let's examine the major applications.

1. Injectable and Parenteral Product Testing

One of the most important applications of a liquid particle counter is particulate matter testing in injectable and parenteral products.

Injectable medicines, including products supplied in ampoules, vials and infusion containers, require appropriate controls for particulate contamination.

Unwanted particles may enter pharmaceutical preparations through:

Manufacturing equipment and processing operations.
Glass containers and rubber closures.
Raw materials and formulation ingredients.
Product transfer and filling operations.
Packaging and handling processes.

A pharmaceutical liquid particle counter helps laboratories quantify subvisible particles in suitable injectable samples.

Testing under USP General Chapter 788 includes two methods:

Method 1 – Light Obscuration Particle Count Test: Measures particles through changes in transmitted light intensity.
Method 2 – Microscopic Particle Count Test: Uses membrane filtration and microscopic examination to determine particle counts.

Light obscuration is generally preferred when the sample is suitable for the technique.

This application is particularly relevant to pharmaceutical manufacturers producing small-volume and large-volume parenteral preparations.

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2. Subvisible Particle Analysis in Pharmaceutical Formulations

Pharmaceutical formulations may contain particles that are not easily detectable through conventional visual inspection.

Subvisible particle analysis helps laboratories understand the particulate characteristics of a formulation and evaluate changes that may occur during development, manufacturing and storage.

A liquid particle counter can support:

Particle size distribution analysis.
Quantification of subvisible particles.
Formulation development studies.
Stability-related investigations.
Evaluation of particulate contamination.

For example, protein-based formulations may develop particles because of aggregation or other formulation-related changes.

However, not all particles are necessarily foreign contaminants. Some may originate from the active pharmaceutical ingredient or formulation itself.

Understanding the source and characteristics of particles is therefore important when interpreting analytical results.

3. Pharmaceutical Water Quality Testing

Water is an essential raw material in pharmaceutical manufacturing. Different grades of pharmaceutical water are used for manufacturing, cleaning, preparation and other controlled processes.

Particulate contamination in pharmaceutical water can be relevant to the overall quality of manufacturing operations.

Liquid particle counting can be used in suitable analytical applications to:

Evaluate particulate levels in water samples.
Investigate contamination trends.
Support water quality monitoring programmes.
Assess changes following filtration or purification.
Assist laboratory investigations into particulate contamination.

The technique may be applied to samples from purified water and Water for Injection (WFI) systems where the analytical method and instrument are appropriate.

Important distinction: Pharmaceutical water monitoring requirements should not be confused with USP 788 acceptance criteria for injectable products. Water systems have their own applicable quality specifications and monitoring requirements.

4. Water for Injection (WFI) and Purified Water Analysis

Water for Injection and Purified Water are important components of pharmaceutical manufacturing processes.

Maintaining appropriate water quality helps pharmaceutical manufacturers control potential contamination throughout production.

A suitable liquid particle counting method can provide additional information about particulate contamination in water samples.

Typical areas of application include:

Monitoring particulate levels in selected water samples.
Investigating filtration system performance.
Supporting contamination troubleshooting.
Comparing particulate measurements before and after suitable filtration processes.
Supporting laboratory quality investigations.

For reliable results, laboratories should consider sample collection, container cleanliness, background particle levels and instrument suitability.

Particle counting is a complementary analytical tool and does not replace other required pharmaceutical water tests, such as conductivity, total organic carbon (TOC), microbial testing or endotoxin testing where applicable.

5. Biopharmaceutical and Protein-Based Formulations

Biopharmaceutical products, including therapeutic proteins and monoclonal antibody formulations, can present unique challenges during particulate matter testing.

Proteins may undergo aggregation or interact with formulation components, potentially producing subvisible particles.

These particles may develop during:

Formulation preparation.
Manufacturing and processing.
Transportation and handling.
Storage and stability testing.
Interactions with packaging components.

Liquid particle counting can help quantify particles in suitable protein-based formulations and support formulation development and quality investigations.

USP General Chapter 787 historically addressed subvisible particulate matter in therapeutic protein injections. USP's 2026 revision proposal for Chapter 788 also addresses therapeutic protein preparations, so laboratories should verify the currently official chapter and applicable product-specific requirements before establishing a testing procedure.

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6. Pharmaceutical Research and Development

Research and development laboratories use particle measurement techniques to understand formulation characteristics and evaluate product performance.

During pharmaceutical development, changes in formulation composition, processing conditions and storage environments may influence particle formation.

A liquid particle counter can support R&D activities such as:

Comparing particle levels in experimental formulations.
Evaluating formulation stability.
Investigating particle formation during development.
Assessing the effects of processing conditions.
Supporting analytical method development.
Comparing particulate characteristics between samples.

For example, researchers developing an injectable formulation may evaluate particulate levels at different development stages to understand how formulation changes influence particle formation.

The results can contribute to a better understanding of product characteristics and help guide further formulation investigations.

7. Quality Control and Batch Testing

Quality control laboratories play a central role in pharmaceutical manufacturing by evaluating whether products meet established quality specifications.

Liquid particle counting can support routine testing workflows where particulate measurement is required.

Its applications in pharmaceutical QC laboratories include:

Testing suitable pharmaceutical liquid samples.
Evaluating particulate contamination.
Supporting batch-related investigations.
Comparing test results across manufacturing batches.
Maintaining documented analytical records.
Supporting product quality investigations.

Automated particle counting can also reduce manual counting activities associated with appropriate analytical procedures.

However, instrument-generated results must be evaluated using approved methods, suitable controls and established laboratory acceptance criteria.

Role of Liquid Particle Counters in USP Standards

Pharmaceutical manufacturers operate within established regulatory and pharmacopoeial frameworks to maintain product quality and consistency.

The United States Pharmacopeia (USP) provides several general chapters addressing visible and subvisible particulate matter in pharmaceutical products.

Understanding these chapters helps laboratories identify appropriate analytical methods for their products.

Understanding USP 788 – Particulate Matter in Injections

USP General Chapter 788, Particulate Matter in Injections, addresses the measurement of subvisible particulate matter in injectable preparations.

It describes two principal analytical methods:

Testing method	Description
Method 1: Light Obscuration	Measures particle counts using changes in transmitted light intensity.
Method 2: Microscopic Particle Count	Uses membrane filtration and microscopic examination to evaluate particles.

The revised chapter officially scheduled for August 1, 2026, includes updated treatment of subvisible particulate matter and therapeutic protein preparations.

The commonly referenced particle size thresholds include 10 µm and 25 µm, with applicable acceptance criteria depending on product volume and category.

For laboratories, selecting the appropriate method requires consideration of the formulation, sample characteristics and applicable compendial requirements.

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USP 787 – Subvisible Particulate Matter in Therapeutic Protein Injections

USP 787 historically provided specific guidance for evaluating subvisible particulate matter in therapeutic protein injections.

Protein-based formulations can behave differently from conventional injectable solutions because of their physical and chemical characteristics.

The chapter addressed considerations such as:

Smaller test sample volumes.
Sample preparation requirements.
Particle measurement.
Formulation-related particulate matter.
Analytical method suitability.

As noted above, the USP 2026 revision proposal indicates that the harmonized USP 788 chapter incorporates material previously addressed in USP 787. Therefore, pharmaceutical laboratories should consult the current official USP-NF edition rather than relying on older chapter references alone.

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Light Obscuration vs. Microscopic Particle Counting

Both techniques are used for subvisible particulate matter testing, but their measurement principles differ.

Parameter	Light Obscuration	Microscopic Particle Counting
Measurement principle	Change in transmitted light	Visual examination under a microscope
Particle detection	Optical signal measurement	Membrane filtration and microscopic observation
Analysis	Instrument-based	Microscopic examination
Typical application	Suitable clear liquid samples	Samples unsuitable for light obscuration
Particle assessment	Estimated particle size and count	Particle count and visual characteristics
Limitations	Sensitive to formulation and sample characteristics	More manual and operator-dependent

Light obscuration is generally preferred under USP 788 when the sample is suitable. However, some suspensions, emulsions, colloids and highly viscous preparations may require microscopic analysis.

The results of these two methods are not automatically interchangeable because they measure particles differently.

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Benefits of Using a Liquid Particle Counter in Pharmaceutical Laboratories

Using an appropriate liquid particle counter can support pharmaceutical testing by providing quantitative particulate measurement.

Here are some of its important benefits.

1. Quantitative Particle Measurement

A liquid particle counter provides numerical information about particle size and particle count, helping laboratories evaluate particulate contamination in suitable samples.

2. Automated Particle Analysis

Automated measurement reduces the need for manual particle counting in applicable testing workflows and helps standardize analytical procedures.

3. Support for Pharmaceutical Quality Control

Particle measurement can contribute to pharmaceutical QC activities, particularly when evaluating subvisible particulate matter in injectable products.

4. Improved Testing Consistency

When operated using validated or appropriately qualified methods, a liquid particle counter can help laboratories achieve more consistent testing procedures.

5. Particle Size Distribution Information

The instrument can provide information about particle counts across defined size ranges, supporting a more detailed evaluation of particulate contamination.

6. Documented Testing Results

Depending on the instrument's software and configuration, measurement results may be recorded, stored and exported for laboratory review and documentation.

It is important to select software and data management capabilities according to the laboratory's documentation, data integrity and regulatory requirements.

How to Choose the Right Liquid Particle Counter for Pharmaceutical Applications

Selecting a suitable pharmaceutical liquid particle counter requires an understanding of the laboratory's testing requirements.

Not every instrument is appropriate for every pharmaceutical formulation or analytical application.

Before purchasing a liquid particle counting instrument, consider the following factors.

1. Particle Size Measurement Range

Evaluate the particle size range required for your application.

The instrument should support the measurement ranges specified in your testing method and be suitable for the expected particle characteristics.

2. Sample Volume and Testing Requirements

Consider the amount of sample available for testing.

This is particularly important when analysing expensive pharmaceutical formulations, therapeutic proteins or samples with limited availability.

3. Measurement Accuracy and Calibration

Calibration and measurement verification are essential considerations when selecting analytical instruments.

Check the availability of appropriate reference standards, calibration procedures and supporting documentation.

4. Software and Data Management

Modern pharmaceutical laboratories require reliable analytical records.

Evaluate the instrument's software capabilities, including:

Test result storage.
Measurement reporting.
Data export.
User access management.
Audit trail functionality, where required.
Electronic record management capabilities.

Do not assume that every instrument is automatically compliant with 21 CFR Part 11. Compliance depends on the complete system configuration, software controls, validation and the laboratory's procedures.

5. Application and Regulatory Requirements

Identify the applicable testing method and regulatory expectations before selecting the instrument.

For example, a laboratory performing particulate matter testing under USP 788 should evaluate whether the instrument and associated method are suitable for the specific pharmaceutical preparation.

6. Technical Support and Instrument Service

Consider the availability of technical assistance, maintenance, calibration support and application guidance.

These factors can contribute to long-term instrument performance and laboratory operational efficiency.

Why Choose Shreedhar Group for Pharmaceutical Testing Instruments?

Selecting suitable analytical instruments is an important part of maintaining reliable pharmaceutical laboratory operations.

Shreedhar Group focuses on pharmaceutical testing and analytical instrumentation, supporting the needs of laboratories and pharmaceutical manufacturing environments.

When evaluating a liquid particle counter, it is important to understand your sample characteristics, measurement requirements and applicable testing methods before selecting an instrument.

Shreedhar Group can be approached to discuss your pharmaceutical testing instrument requirements and identify a suitable solution based on your application.

Whether you are evaluating particulate contamination in injectable products, reviewing laboratory testing requirements or planning to upgrade your analytical capabilities, choosing the right instrument should begin with a clear understanding of your testing objectives.

Looking for a suitable Liquid Particle Counter for your pharmaceutical laboratory?

Connect with Shreedhar Group to discuss your application requirements and explore relevant pharmaceutical analytical instruments.

Conclusion

Particulate contamination control is an important consideration in pharmaceutical manufacturing, particularly for injectable and parenteral products.

A Liquid Particle Counter provides valuable quantitative information about the size and number of particles present in suitable liquid samples. Its applications extend across injectable product testing, subvisible particle analysis, pharmaceutical water investigations, biopharmaceutical research and routine quality control.

Technologies such as light obscuration help pharmaceutical laboratories measure particles efficiently, while pharmacopoeial methods provide guidance on selecting appropriate testing procedures.

However, choosing the right instrument requires careful consideration of sample characteristics, particle measurement requirements, calibration and applicable regulatory standards.

For pharmaceutical manufacturers and laboratory professionals, understanding these applications is an important step towards establishing reliable particulate matter testing practices.

Looking for pharmaceutical analytical instruments?

Connect with Shreedhar Group to discuss your laboratory testing requirements and explore suitable pharmaceutical testing solutions.