Inductively coupled plasma mass-spectrometry (ICP-MS) is an exceptionally sensitive technique, but this strength makes it vulnerable to matrix effects & interferences that can skew data. Easy improvements to a method can optimise sensitivity & allow analysts to get the best out of their ICP-MS instrument, here are our top 3 recommendations.

1. Matrix matching is paramount

Differences between your calibration standards & your samples can lead to signal suppression or enhancement.

• Action: ensure your calibration standards have the same acid concentration as your samples as well as the same type of acid
• Internal standards: choose an internal standard (Figure 1) suitable for your analyte, ensuring it is close in mass to those elements you are trying to analyse.

2. Managing polyatomic interferences

Species formed in the plasma (like ⁴⁰Ar³⁵Cl⁺ overlapping ⁷⁵As⁺) can be a common issue

• Helium mode: use helium collision mode with kinetic energy discrimination (KED). As quadrupoles cannot distinguish between mass, KED is used as it ignores mass and focuses on the size of the polyatomic ions. As these molecules are larger than single ions, they will experience more collisions with the helium and lose additional energy as opposed to single-atom ions, the polyatomic ions cannot overcome the energy barrier at the exit to the detector and are rejected by the system. This helps eliminate false positives and lowers detection limits by dropping the background noise, allowing better trace analysis

3. Maintaining your interface cones

The interface is the most fragile part of the instrument. Worn or dirty sampler & skimmer cones (Figure 2) are a primary cause of poor analytical signal, resulting in low signal and poor recovery rates of internal standards.

• Handling: never let the fine tip of the sampler or skimmer cones touch any surface. Even minor contact can deform the orifices, disrupting sensitivity in analysis as the ability to pull ions efficiently into the vacuum zone drops dramatically
• Cleaning: regular maintenance is necessary to remove matrix deposits, but “over-maintenance” can also cause damage by degrading the orifices. For example, using a strong acid to clean your cones, can strip metallic layers over time causing the base metal to become exposed which can corrode and introduce contamination to your samples

To find out more about optimising ICP-MS analysis, join our:

• Applied ICP-MS
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