Determination of Particle Number Concentration by Light Obscuration (LO) / Single Particle Optical Sensing (SPOS) (CAT#: STEM-MB-2270-CJ)

Light obscuration is an analytical technique in which the individual particles in a liquid suspension are placed in-between a laser light source and a detector. The laser light source is used to illuminate the individual particles resulting in a shadow or a blockage of light. This shadow or blockage is often called “obscuration”, which is how this particular analytical technique was granted its name. Light obscuration or the reduction of light intensity is measured by the detector. The detector will then process the measured signal and use it to display a comprehensive calibration curve. This curve is then read to quantify particles and determine their size.

Biomedical; Biopharmaceuticals; Pharmaceutical

1. Prepare samples.
2. Dilute sample preparation, more concentrated preparations may require substantial dilution.
3. Operate the instrument according to the manual.
4. Analyze data on imaging particle analysis system.

• Sample: Particle-based APIs (e.g., VLPs, liposomes, polymeric nanoparticles); Virus Particle; Protein-based Formulations; Sterile Preparations.
• Equipment: Particle Counter Machine.
• Imaging Particle Analysis System.

1. Light obscuration (LO) is the most widely used subvisible particle assay in the pharmaceutical industry and is the preferred compendial method (USP, EP, JP).
2. LO allows counting and sizing of subvisible particles in the size range from about 1 to 200 µm.
3. Light obscuration (LO) do not need for extra chemicals or consumables
4. When using a light obscuration particle counter, the sample must be presented in a dilute form for analysis.