LimsPulse
TGA · Calibration procedure

Mass calibration

Checks the TGA microbalance with certified milligram weights, and optionally its overall performance with calcium oxalate monohydrate.

Photo of a TGA
Photo: Luigi Chiesa, CC BY 3.0 (cropped), via Wikimedia Commons
PURPOSE

Why this is checked

Every TGA result is a percentage mass loss, so the balance must read mass correctly across the sample range.

Frequency

Typically every 6–12 months, with a performance check more often as defined in your SOP.

Learn how the TGA works
YOU WILL NEED

Standards & tools

  • Certified milligram weights (for example 10, 50 and 100 mg) traceable to national standards
  • Optional: calcium oxalate monohydrate for a performance check (theoretical steps about 12.3% water, 19.2% carbon monoxide and 30.1% carbon dioxide)
BEFORE YOU START

Prerequisites

  • Balance stable and furnace at room temperature
  • Weights handled with tweezers only
PROCEDURE

Step by step

  1. 1Tare the empty pan.
  2. 2Place each certified weight in the pan and record the reading once stable.
  3. 3Calculate the error for each weight.
  4. 4Optionally run calcium oxalate monohydrate from ambient to about 900 °C and compare each mass-loss step with theory.
RECORD

Example observation table

Certified mass (mg)Observed (mg)Error (mg)% error
10.00010.004+0.004+0.04
50.00049.987−0.013−0.026
100.000100.021+0.021+0.021
CALCULATION

How to calculate the result

% error = (Observed − Certified) ÷ Certified × 100
  1. 50 mg weight: (49.987 − 50.000) ÷ 50.000 × 100 = −0.026%
  2. Calcium oxalate monohydrate (M = 146.11 g/mol): water 18.02 ÷ 146.11 × 100 = 12.33%
ACCEPTANCE CRITERIA

Pass if

  • Error within the limit in your SOP or the manufacturer's specification (commonly about ±0.1% or a stated µg value).
IF IT FAILS

What to do

  • Label the instrument 'Out of calibration' and stop using it.
  • Investigate the cause and arrange adjustment or repair.
  • Assess the impact on results generated since the last passing calibration.
  • Repeat the full calibration before returning it to use.
MORE

Other TGA 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