Liquid Particle Counter (Liquid Particle Counter)

Liquid Particle Counting is a mandatory quality control technique for injectable pharmaceutical products, providing quantitative enumeration of sub-visible particulate matter that could pose serious patient safety risks if present at unacceptable levels. Sub-visible particles (2-100 micrometer diameter) are invisible to the naked eye but can cause emboli, immune reactions, and vessel occlusion when administered intravenously.

Auriga Research operates light obscuration-based liquid particle counters compliant with USP <788> and EP 2.9.19. The light obscuration principle flows the liquid sample past a collimated light beam; each particle crossing the beam reduces the transmitted light intensity in proportion to its cross-sectional area, generating a pulse that is counted and sized by the instrument electronics. Modern particle counters characterize hundreds of particles per second, providing statistically robust counts at the >=10 micrometer and >=25 micrometer thresholds specified in USP <788>.

For large-volume parenterals (greater than 100 mL), USP <788> limits are no more than 25 particles/mL at 10 micrometers and 3 particles/mL at 25 micrometers. For small-volume parenterals (no more than 100 mL), limits are no more than 6000 particles/container at 10 micrometers and 600 particles/container at 25 micrometers.

Applications

Particulate matter testing for injectables

USP 788 compliance testing

Clean room water quality monitoring

Pharmaceutical manufacturing process control

IV fluid quality assurance

Key Capabilities at Auriga Research

  • Sub-visible particle detection (2-25 μm)
  • USP 788 compliant methodology
  • Light obscuration principle
  • Automated counting and reporting

Testing Services Using Liquid Particle Counter

Liquid Particle Counter supports multiple Auriga testing verticals — the same instrumentation and expertise serving different regulatory requirements and industry sectors.

Pharmaceutical Testing

Frequently Asked Questions

What is sub-visible particulate matter testing for injectables?
Sub-visible particulate matter testing detects and counts microscopic particles (2-100+ micrometers) in injectable pharmaceutical products that are invisible to the naked eye but potentially harmful when administered intravenously. Sources include protein aggregates in biologic products, silicone oil from syringe plungers, glass particles from vials, metal particles from manufacturing equipment, and rubber particles from stoppers. USP <788> requires particulate testing for all injectable products, with limits at 10 micrometer and 25 micrometer particle sizes.
What does USP 788 require for particulate matter testing?
USP <788> specifies two complementary methods: (1) Light obscuration particle count test for most liquid parenterals, and (2) Microscopic particle count test for referee testing and opaque/viscous solutions. Acceptance limits for large-volume parenterals: no more than 25 particles/mL at 10 micrometers and 3 particles/mL at 25 micrometers. For small-volume parenterals: no more than 6000 particles/container at 10 micrometers and 600 particles/container at 25 micrometers.
Why is particulate matter testing critical for biologic drug products?
For biologic drug products (monoclonal antibodies, peptides, proteins), protein aggregates are the primary particulate concern. Protein aggregates can trigger immune responses including anti-drug antibody formation, which can reduce drug efficacy or cause immune-mediated adverse reactions. ICH Q6B and FDA guidance classify protein aggregates by size: sub-micron (0.1-1 micrometer), sub-visible (1-100 micrometers), and visible (greater than 100 micrometers). Comprehensive biologic characterization also requires DLS for sub-micron aggregate quantification.
How does cleanroom water quality monitoring use particle counting?
Cleanroom water quality monitoring uses liquid particle counting to verify that water systems (Purified Water, Water for Injection) used in pharmaceutical manufacturing meet particulate cleanliness specifications. USP <643> and EP monographs specify particle limits for WFI and Purified Water. Continuous or periodic monitoring of water distribution loops detects biofilm shedding events, filter failures, or contamination events. Auriga provides water system validation services including particle count monitoring per USP <1231>.

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