ICP-MS analysis

What is ICP-MS?

ICP-MS is a high throughput elemental analysis method that is capable of detecting most of the elements in the periodic table. Modern ICP-MS instruments offer linear dynamic ranges up to twelve orders of magnitude. This enables simultaneous analysis of major and minor elemental components of the sample.

Besides low-concentration (ppb=parts per billion=µg/l) accuracy, ICP-MS performs reliably in ultra-low concentrations (ppt=parts per trillion=ng/l and even ppq=parts per quadrillion). The method is capable of measuring atomic mass ranging from 7 to 250, which means that it detects elements from lithium to uranium. ICP-MS can also distinguish different isotopes of elements.

How does ICP-MS work?

ICP-MS uses high-temperature plasma that breaks down the chemical compounds in the samples to their atomic ions. After this, mass spectrometry is used to detect and quantify the ions to distinguish different elements and, in some cases, their isotopes.

Inductively coupled plasma-mass spectrometry is most often used to analyze solid or liquid samples, but gas analysis is also possible. Most common ICP-MS instruments rely on liquid injection, meaning that solid and gaseous samples must be dissolved into liquids before the analysis. With solid samples, this is most often achieved through acid digestion with hot mineral acids. An example of such a pretreatment method for solids is vapor phase decomposition, which can be combined with ICP-MS in VPD-ICP-MS analysis. Gases, on the other hand, can be trapped in suitable liquids by bubbling.

If sufficient results cannot be achieved through the pretreatment of solid or gaseous samples, special instruments can be used to investigate these samples without dissolving pretreatment. For example, LA-ICP-MS (laser ablation inductively coupled plasma mass spectrometry) can be used to analyze the surfaces of solid samples directly.

The difference between ICP-MS and ICP-OES

The principle of ICP-MS is measuring the mass of the atoms through mass spectrometry, as explained above. ICP-OES (inductively coupled plasma-optical emission spectroscopy) on the other hand, is based on analyzing the wavelengths of the excited atoms and ions within the elements in the sample.

The difference in use cases is that ICP-OES is a more robust method for analyzing samples that have a higher amount of total dissolved solids and stricter regulations. Examples of this type of sample are groundwater, wastewater, soils, and solid waste.

What is ICP-MS analysis used for?

ICP mass spectrometry is most often used in multi-element trace studies. It can, for example, be used to analyze heavy metal contamination of food, water, consumer goods, or pharmaceutical products. Other trace metal studies are also common. In solvent purity assays, ICP-MS can be combined with GC-FID and Karl Fischer titration to obtain comprehensive data on possible contaminants.