Sub-Visible Particle Counting

At RSSL, particle counting is carried out using a variety of techniques that are compliant with USP and PhEur pharmacopoeia for parenteral/ injectible solutions, ophthalmic solutions, Petrochemicals and water, these include:

1. Sub-visible particle counting using a light obscuration particle counter

2. Sub-visible particle counting investigation using a light microscope

3. Visible particle assessment

These methods are frequently used to monitor filtering efficiency and/or as a quality control in batch preparations.

1. The light obscuration particle counter is supplied by Particle Measuring Systems (PMS)

• Particle size standards are used routinely prior to testing to ensure accurate results. 
• Testing is carried out in a Laminar flow cabinet.
• Permissible for size range 2 - 125 mm @ various integers i.e. 2, 5, 10, 15, 25 mm etc.

2. Sub-visible particle counting using a light microscope, based upon USP <788>. 

• Handling of samples and preparation of samples is carried out in a Laminar flow cabinet, to minimise contamination of samples.
• This method allows a visual assessment of precipitates and particulates in a solution, with the option of photographic evidence of the observations.

3. A visible particle assessment is carried out in accordance with PhEur 2.9.20.

•  A count of visible particles present in a small volume solution e.g. 2 - 20 ml.

• A brief description of observed particles e.g. colour, shape and an estimation of size.