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ICP-OES · Calibration procedure

Wavelength calibration

Aligns the spectrometer so that each element's emission line falls exactly where the software expects it, using a multi-element calibration solution.

Photo of a ICP-OES
Photo: Cyberwork 95, CC BY-SA 4.0 (cropped), via Wikimedia Commons
PURPOSE

Why this is checked

If the wavelength scale shifts, the software measures beside the peak instead of on it. Intensity falls and background correction points may land on the peak, giving wrong results.

Frequency

Typically wavelength calibration daily or per manufacturer recommendation, and detection limits every 6 or 12 months and after major repair, as defined in your calibration SOP.

Learn how the ICP-OES works
YOU WILL NEED

Standards & tools

  • Manufacturer's multi-element wavelength calibration solution (traceable), or a mix such as Mn, Cu, Zn, Ba, Al, Na at known concentrations in dilute nitric acid
  • Dilute nitric acid blank
BEFORE YOU START

Prerequisites

  • Plasma lit and stable for at least 15–30 minutes
  • Spectrometer at its controlled temperature and optics purged
PROCEDURE

Step by step

  1. 1Aspirate the blank, then the wavelength calibration solution.
  2. 2Run the instrument's wavelength calibration routine; it locates the peak centre of each reference line.
  3. 3Record the measured peak positions and the deviation from the reference wavelengths.
  4. 4Accept and save the new calibration if all lines are within limits.
RECORD

Example observation table

LineReference λ (nm)Measured λ (nm)Deviation (nm)
Zn 213.857213.857213.859+0.002
Mn 257.610257.610257.612+0.002
Cu 324.754324.754324.751−0.003
Al 396.152396.152396.154+0.002
Ba 455.403455.403455.400−0.003
CALCULATION

How to calculate the result

Deviation = Measured peak wavelength − Reference wavelength
  1. Mn 257.610 nm measured at 257.612 nm
  2. Deviation = 257.612 − 257.610 = +0.002 nm
  3. Within the example tolerance of ±0.005 nm: passes
ACCEPTANCE CRITERIA

Pass if

  • Each line within the manufacturer's tolerance (often a few thousandths of a nm, or within a stated number of detector pixels). Use the limit in your SOP.
  • The software calibration routine reports 'pass' for all lines.
IF IT FAILS

What to do

  • Confirm the calibration solution is correct and freshly prepared.
  • Let the optics reach temperature and the plasma stabilise, then repeat.
  • If it still fails, label 'Out of calibration' and call service.
MORE

Other ICP-OES 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