Why is quantitative analysis difficult with secondary ion mass spectrometry?

In secondary ion mass spectrometry (SIMS), quantitative analysis is difficult primarily due to the matrix effect.12

The relative ion yields—the efficiency with which atoms or molecules are converted into secondary ions—vary significantly depending on the chemical nature of the surface being analyzed. Because these sensitivity variations are highly dependent on the host material's composition, the intensity of the signal does not always correlate directly with the concentration of a specific species.12

Key factors contributing to this difficulty include:

• Sensitivity Variations: The sensitivity of SIMS can fluctuate by as much as ${10}^5$ between different elements, making it impossible to perform absolute quantitative analyses without complex calibration.1
• Matrix Sensitivity: Even minor changes in the sample matrix can cause significant intensity shifts, leading to higher relative uncertainties in measurements compared to other surface analysis techniques.1
• Electronegativity Influence: As a general rule, electropositive elements exhibit higher sensitivity in positive-ion SIMS, while electronegative elements show higher sensitivity in negative-ion SIMS, further complicating uniform quantification.1

While SIMS is considered the least quantitative of the surface analytical techniques, it remains highly valued for its exceptional sensitivity, capable of detecting materials at the parts-per-million level.1