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Liquid particle counter · Calibration procedure

Counting accuracy

Runs a reference suspension of known particle concentration and checks that the counter reports the certified count. Sample volume accuracy is checked at the same time.

PURPOSE

Why this is checked

Even with correct sizing, the counter must count every particle and draw the right volume. Errors in counting or volume change the particles-per-container result directly.

Frequency

Typically at each sizing calibration and at the interval in your SOP (some labs check monthly or before each test series).

Learn how the Liquid particle counter works
YOU WILL NEED

Standards & tools

  • Certified count reference suspension (e.g. USP Particle Count RS or a traceable 15 µm count standard)
  • Particle-free water
  • Calibrated analytical balance and thermometer (for gravimetric volume check)
BEFORE YOU START

Prerequisites

  • Sizing calibration valid
  • Blank counts within limit
PROCEDURE

Step by step

  1. 1Volume check: draw the set volume of water (e.g. 10 mL), collect and weigh it, and convert to volume using the density of water.
  2. 2Mix the count standard gently as its certificate describes; degas.
  3. 3Run the standard in replicate portions and record counts per mL at the certified size.
  4. 4Calculate the mean count and the % difference from the certified value.
RECORD

Example observation table

CheckCertified / setObserved% difference
Sample volume (25 °C, ρ = 0.99705 g/mL)10.00 mL9.93 g → 9.96 mL−0.4
Count standard (≥ 15 µm, per mL)30002890−3.7
CALCULATION

How to calculate the result

% difference = (Observed count − Certified count) ÷ Certified count × 100; Volume = Mass ÷ Density
  1. Volume: 9.93 g ÷ 0.99705 g/mL = 9.96 mL; (9.96 − 10.00) ÷ 10.00 × 100 = −0.4%
  2. Count: (2890 − 3000) ÷ 3000 × 100 = −3.67%
ACCEPTANCE CRITERIA

Pass if

  • Mean count within the limits stated on the reference suspension certificate (commonly about ±10%).
  • Sample volume accuracy typically within ±5% (see the current chapter).
IF IT FAILS

What to do

  • Check dilution, mixing and degassing, and repeat.
  • Check the syringe sampler for air and leaks.
  • If it still fails, take the counter out of use and get it serviced.
MORE

Other Liquid particle counter calibrations

In LimsPulse · Calibration Management

LimsPulse schedules this calibration, records the result against limits, and blocks the instrument everywhere if it fails or goes overdue.

See how