LimsPulse
Dosage-form testing

Liquid Particle Counter (Light Obscuration)

Counts and sizes sub-visible particles in injections by passing the liquid through a narrow light beam. Each particle casts a shadow whose size gives the particle size. Used for the USP <788> particulate matter test.

  • Pharmaceutical (parenterals)
  • Biotech
  • Medical devices
  • Industrial fluids
Follow your site SOP
This is a typical operating sequence for learning. Your instrument model and approved SOP take precedence.
STAGE 1

Environment and blank

  1. 1Work in a laminar air flow cabinet; wear powder-free gloves.
  2. 2Clean glassware with particle-free water (filtered through 1.2 µm or finer).
  3. 3Run a blank of particle-free water: it should meet the environment limit in the chapter (commonly no more than 25 particles ≥ 10 µm in 25 mL).
  • Most failures come from contamination by the analyst or glassware, not the product.
STAGE 2

Sample preparation

  1. 1Wipe the outside of containers and invert them gently about 20 times to mix.
  2. 2Open carefully; pool small units if the volume per container is too small for testing.
  3. 3Allow the pooled sample to stand or apply gentle vacuum so bubbles disappear.
  • Do not shake hard; it makes bubbles that are counted as particles.
STAGE 3

Measurement

  1. 1Run four portions of at least 5 mL each.
  2. 2Discard the result of the first portion.
  3. 3Average the counts of the remaining portions.
  4. 4Calculate particles per container (small volume) or per mL (large volume) and compare with the limits.
  • If counts are near the coincidence limit, the result is not valid; use a different volume or the microscopic method.
In LimsPulse · Calibration Management

Keep every Liquid particle counter in control: usage logs, calibration and maintenance schedules, and automatic blocking of overdue instruments.

See how