In the pharmaceutical industry, patient safety is always the highest priority. One of the key quality attributes for injectable products is the control of visible and sub-visible particulate matter. Even microscopic particles can impact product quality, efficacy, and patient safety.
A Liquid Particle Counter (LPC), operating on the Light Obscuration Principle, plays a vital role in detecting, sizing, and counting particles present in liquid pharmaceutical products, purified water, and Water for Injection (WFI) systems. By measuring the reduction of laser light caused by particles passing through a flow cell, the instrument provides accurate particle size distribution and count data in compliance with regulatory requirements such as USP <788>, EP 2.9.19, and JP.
Liquid particle counters work on the principal of either light scattering or light blocking. A sample is drawn through a chamber with a light source. Today’s modern liquid sensor’s use a laser diode as the source of illumination. Liquid Particle Counters depending on the size sensitivity use either a light blocking or light scattering technique.
The light blocking optical particle counter method is typically useful for detecting and sizing particles greater than 1 micrometer in size and is based upon the amount of light a particle blocks when passing through the detection area of the particle counter.
Light scattering uses a high intensity light source to illuminate the particle as it passes through the detection chamber. The particle passes through the light source (typically a laser) if light scattering is used, then the redirected light is detected by a photo detector.
If light blocking (obscuration) is used the loss of light is detected. The amplitude of the light scattered or light blocked is measured and the particle is counted and binned into the correct size channel.
From a Quality Control (QC) perspective, LPC testing is much more than a compliance activity. It is a critical safeguard that verifies the integrity of sterile products throughout development, validation, stability studies, and commercial manufacturing. Effective particle monitoring helps identify contamination risks early and supports a robust Pharmaceutical Quality System (PQS).
Understanding the science behind analytical instruments enables us to make better decisions and continuously improve quality standards.
Read also: Difference Between Viable and Non-Viable Partcles