Coulter Counter

The Coulter Counter, based on the electrical sensing zone (ESZ) method, is a widely recognized technique for precise particle size analysis. As particles suspended in an electrolyte solution pass through a small aperture, they displace an equivalent volume of the conductive fluid, causing a momentary change in electrical resistance. This resistance change is proportional to the particle volume, allowing for highly accurate size distribution measurements (typically 0.4–1,600 µm). Unlike optical methods, the coulter counter is unaffected by particle transparency, refractive index, or color, making it ideal for analyzing complex pharmaceutical formulations, including opaque suspensions, liposomes, and microspheres.

Applications in Pharmaceutical Partical Analysis

In pharmaceutical development, particle size distribution (PSD) significantly impacts drug performance, including dissolution rate, bioavailability, stability, and manufacturability. The coulter counter is particularly valuable in:

• Formulation Optimization: Ensuring uniform particle size in suspensions, emulsions, and solid dosage forms.
• Quality Control: Detecting aggregates or oversized particles in injectables (e.g., vaccines, monoclonal antibodies).
• Process Development: Monitoring milling, crystallization, and spray-drying processes in real time.

The coulter counter offers several critical advantages over alternative techniques like laser diffraction (LD) or dynamic light scattering (DLS). Unlike LD, which relies on light scattering models and assumes spherical particles, the coulter counter directly measures particle volume, eliminating shape-related biases. Compared to DLS, which struggles with polydisperse samples, the coulter counter provides high-resolution sizing even in complex mixtures. Additionally, it does not require sample dilution at high concentrations, avoiding artifacts introduced by dilution steps. Its ability to analyze conductive and non-conductive particles without optical interference makes it indispensable for challenging formulations, such as lipid nanoparticles (LNPs) and protein aggregates. Furthermore, the technique's dynamic range (spanning nanometers to millimeters) allows seamless analysis across different stages of drug development, from early-stage research to commercial batch release.

PharmaAnalytica's Technology Platform

PharmaAnalytica's Coulter Counter-Based Particle Analysis

PharmaAnalytica's coulter counter services provide accurate, regulatory-ready particle analysis to support drug development from preclinical to commercial stages.

High-Precision Analysis with Regulatory Compliance

PharmaAnalytica's coulter counter services adhere to cGMP and ISO 17025 standards, ensuring data integrity for regulatory submissions (e.g., FDA, EMA). Our protocols align with USP <788> and EP 2.9.19, providing reliable particulate counts for parenteral products.

Customized Method Development

We optimize measurement parameters (aperture size, electrolyte selection) for diverse samples, including liposomes, polymeric micelles, and protein therapeutics. Our team validates methods for challenging matrices (e.g., high-viscosity or low-conductivity solutions).

High-Throughput Capability

With automated sample handling and multi-aperture systems, PharmaAnalytica delivers results for routine testing and large-scale batch analysis, accelerating formulation development.

Integrated Multi-Technique Approach

We complement coulter counter data with SEM, DLS, or NTA for comprehensive characterization, offering insights into particle morphology, charge, and aggregation state—critical for robust drug product design.

By combining unmatched technical capabilities with tailored solutions, we help pharmaceutical companies optimize formulations, ensure quality, and expedite time-to-market.