LimsPulse
IC · Calibration procedure

Pump flow rate accuracy

Checks that the IC pump delivers the set flow, by weighing water collected over a timed interval.

Photo of a IC
Photo: Datamax, Public domain (cropped), via Wikimedia Commons
PURPOSE

Why this is checked

Ion chromatography identifies ions by retention time and quantifies them by peak area. Both depend on a stable, accurate flow from the metal-free pump.

Frequency

Typically every 6 months, and after major repair or relocation, as defined in your calibration SOP.

Learn how the IC works
YOU WILL NEED

Standards & tools

  • Calibrated analytical balance
  • Calibrated stopwatch
  • Calibrated thermometer
  • Deionised water (18.2 MΩ·cm)
  • Tared, capped plastic collection vial
BEFORE YOU START

Prerequisites

  • Bypass the column and suppressor with a restriction tubing (or as the manufacturer specifies), or keep them in line if the procedure says so
  • Switch off the eluent generator and suppressor if bypassed
  • Purge the pump and check for leaks
PROCEDURE

Step by step

  1. 1Pump deionised water at 0.5 mL/min and let the flow stabilise.
  2. 2Collect the outlet into a tared vial for exactly 10.00 minutes and weigh it.
  3. 3Convert mass to volume using the density of water at the measured temperature.
  4. 4Repeat at 1.0 mL/min and 1.5 mL/min, or at the flows your methods use.
RECORD

Example observation table

Set flow (mL/min)Time (min)Mass (g)Volume (mL)Actual flow (mL/min)% error
0.510.004.9684.9830.4983−0.34
1.010.009.99110.0211.0021+0.21
1.55.007.5117.5341.5067+0.45
CALCULATION

How to calculate the result

Volume = Mass ÷ Density; Actual flow = Volume ÷ Time; % error = (Actual − Set) ÷ Set × 100
  1. Set 1.0 mL/min; 9.991 g collected in 10.00 min at 25 °C (density 0.9970 g/mL)
  2. Volume = 9.991 ÷ 0.9970 = 10.021 mL
  3. Actual flow = 10.021 ÷ 10.00 = 1.0021 mL/min
  4. % error = (1.0021 − 1.0) ÷ 1.0 × 100 = +0.21%
Use the Flow rate accuracy calculator
ACCEPTANCE CRITERIA

Pass if

  • Actual flow typically within ±2.0% of the set value at each flow, or as per the manufacturer's specification and your SOP.
IF IT FAILS

What to do

  • Label the instrument 'Out of calibration'.
  • Check for leaks and salt deposits, worn seals and check valves; arrange service.
  • Assess the impact on results since the last passing calibration and repeat after repair.
MORE

Other IC 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