Inductively Coupled Plasma Mass Spectrometry (ICP-MS) is a combined analysis of inductively coupled plasma (ICP) with mass spectrometry (MS). ICP-MS provides ion using ICP and then the sample is nebulised, evaporated, atomized and ionsisable before being detected and analyzed by mass spectrometer. It is extremely sensitive, dynamic and simultaneous multi-element analytical so the use of this method for trace element analysis is very common.

Importance of ICP-MS

The importance of ICP-MS is its ability to detect and quantify different metals and non-metals, such as volatile metal compounds, nanoparticles, stable isotope tracers and pharmaceutical components. It has significant applications in environmental samples, biological samples, food samples, and semiconductor materials. In environmental samples, for example, ICP-MS can detect small amounts of toxic metals in water, soil, sediments and atmospheric granules. In biomedical applications, ICP-MS is applied to analyse metal elements and their metabolic pathways in biological blood, urine and tissue samples.

Historical Development and Evolution of ICP-MS

ICP-MS is a newer analytical method that brings the benefits of ICP as an ionization source together with mass spectrometry. It has the most important characteristics of high sensitivity, high dynamic range, low detection limits and can pick up several things simultaneously. ICP-MS was first invented in the late 1970s by researchers looking for alternatives to the standard technique, Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). Due to these significant spectral interferences, the goal of ICP-OES research was to combine ICP-OES's ionisation efficiency with mass spectrometry and so developed ICP-MS. In 1983, commercial ICP-MS came into existence with the first commercial version.

History of ICP-MS

Initially, ICP-MS was a simple test of simple samples, and its instruments were complicated and expensive. But technology made ICP-MS gradually defeat problems like signal drift, and grew into a fast, simple, powerful tool. Remarkably, in the 1990s ICP-MS became very popular for complex samples in fields as diverse as environmental science, geology and biomedicine.

As ICP-MS developed, so did many other innovative technologies, including collision/reaction cell (CRC) technology, which reduces spectral interference and improves multi-element detection. Also, most new ICP-MS machines have quadrupole mass analyzers that are more sensitivity and precision.

ICP-MS Process: How It Works

1. Sample Introduction

The sample is introduced in liquid form into the ICP-MS system first. Typical liquid samples go via a peristaltic pump and spray chamber, and become a fine aerosol with a nebuliser. They can be reacted into aerosols with laser ablation or electrothermal evaporation in the case of solids.

2. Plasma Generation and Ionization

The produced aerosol reaches the plasma, excited by radiofrequency energy in the form of argon gas, and so can reach temperatures of around 10,000 K, at which time molecules in the sample are destroyed into atoms, which then lose electrons to become positive ions.

3. Ion Extraction and Focusing

In the plasma, positive ions get pushed to the vacuum system through the interface area. The interface separates the ions from the neutral matter in the plasma, which reduces the background noise. They concentrate the ions with electrostatic lenses or electromagnetic fields to prepare them for mass analysis.

4. Mass Analysis

The ion targets in the mass analyzer are separated by mass/charge ratio (m/z). Typical mass analyzers are quadrupoles, magnetic sector and time-of-flight analyzers.

5. Detection and Quantification

Separated ions go through a detector, and get translated into electrical signals. They are then amplifiated and computed concentrations of each element in the sample.