Section 68 Internal Standards (Internal Accuracy Tests are Misnamed)

• Library: DWI Experts and the Science of Chemical Tests 2014

Internal standards are not true calibration (accuracy) checks and are just checks of the stability and consistency of the IR (infrared) signal. Internal standards are beam attenuators, meaning they block some transmittance of light to the detector. An internal standard is a means of checking the transmittance of the IR signal to the detector against the range of absorbance that would be expected for that particular beam attenuator.

Fuel cell machines like the EC/IRs do not use an internal standard.

Unlike external standards, internal standards only check the...