The 8 Fundamentals of ICP-MS

Healthcare

A single quadrupole ICP-MS has six basic compartments: the sample introduction mechanism, inductively coupled plasma (ICP), interfacing, ion lenses, particle analyzer, and sensor.

Iodine, manganese, copper, selenium, and zinc are among the necessary elements that are checked for nutrition-related reasons. These substances are crucial for various biological functions, such as oxygen and electron transport, hormone production, and activation of biological events. 

One or more pathological diseases could be brought on by disruptions in the usual homeostasis of these components.

What To Know About It

ICP-MS is an analytical method that detects tiny amounts of elements in biological fluids. Although some facilities continue to employ outdated methods like atomic absorption and emission, there has been a slow transition toward ICP-MS, notably in the last ten years. 

Clinical scientists should be knowledgeable about the analytical features of ICP-MS, the possibility for spectroscopic and non-spectroscopic interference, and techniques that can be used to prevent or lessen these problems because this transition is expected to continue.

ICP-OES and ICP-MS both have a multi-element nature and a great sample throughput, while ICP-MS enables more sensitive measurements. The presence of spectral and non-spectral interferences and the high cost of ICP-MS detection are disadvantages and drawbacks.

How Does It Function?

An ICP-MS apparatus ionizes the components in a test using a plasma (ICP) and then utilizes a mass spectrometer to analyze the ions (MS). The fundamentals of ICP-MS are the following: 

  • A technique for introducing samples that produces a thin aerosol mist from liquid samples
  • Plasma (ICP) to change the aerosol’s components into ions
  • Interface for ions extraction into a vacuum system
  • Ion lenses concentrate the ions and distinguish them from background signals.
  • A collision/reaction cell (CRC) separates analyte ions from competing ions.
  • Mass analyzer for mass-based plasma ion filtering
  • Electron Detector
  • Data Analysis

1. Sample Introduction

Input samples to an ICP-MS system are typically liquids. The liquid sample must first be divided into tiny droplets before being added to the argon plasma. Instruments for ICP-MS are generally made to analyze liquids. Electrothermal vaporization and laser ablation are two methods that can be used to analyze solid materials directly.

A peristaltic compressor or self-aspiration can be used to deliver the sample solution into a nebulizer, which produces an aerosol of tiny droplets. The fluidity, purity, and even the sample quantity that can be used for analysis can all affect the kind of nebulizer employed.

2. ICP

The ICP torch, a collection of circular quartz tubes enclosed at one end by an RF coil, is used to create the plasma by pumping argon through it. The coil’s energy from the RF generator combines with the argon to create the plasma.

The atoms take in more energy as they move through the plasma, and finally, they release one electron to produce singly charged ions. Only charged ions leave the plasma and move into the interface area.

3. Interface

The mass analyzer vacuum chamber and the plasma are divided by a pair of circular nickel (or platinum) cones. A mechanical roughing pump keeps the interface tension between the cones constant. 

As ions enter this boundary region, the sharp drop in pressure leads them to expand supersonically, creating a so-called free jet. At this pressure, charged surfaces known as electrostatic lenses may effectively guide ions.

4. Ion Lenses

The ion lens system’s job is to direct the ion beam toward the mass analyzer while blocking the path of photons and other neutral species that may otherwise reach the detector. A high-pressure pump and a mechanical roughing pump, which comprise the primary parts of the vacuum system, are combined to complete this operation.

5. Collision/Reaction Cell 

Chemistry is used by reaction cells, which benefit from exothermic (quick) and endothermic (slow) reactions. An active ion tends to react with interfering ions. Sample solution ions react endothermically while gasses react exothermically. Interferent ions will change into a different species when passed through a mixture of reactive gas and analyte ions.

6. Mass Analyzer

Ions move via the ion optical system before reaching the mass analyzer. ICP-MS has utilized various mass analyzer types, including quadrupole, magnetic sector, and time-of-flight (TOF). The quadrupole mass analyzer is by far the most popular kind used for typical clinical, biochemical applications.

7. Detector

An electron multiplier is the most used ICP-MS detector. Positively charged analyte ions strike the detector’s initial dynode, maintained at an extremely high negative energy. This process, known as secondary emission, keeps on and eventually results in an intensification cascade that amplifies the signal to a size that can be accurately quantified as an ion “count.”

8. Data Analysis

The program converts the ion counts recorded by the detector into data the operator could find more useful. The output of the results can be produced using unique report formats or transmitted to a laboratory information management system or another data-handling system.

Conclusion

ICP-MS is a powerful analytic method for finding clinically relevant trace amounts in biological fluids. ICP-MS is particularly appealing for the clinical laboratory because of its many features. 

Despite the high specificity of mass spectrometry, researchers and medical professionals should be aware of the possibility of interference and analytical issues that could compromise the accuracy of reported data.

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The views expressed in this article are those of the authors and do not necessarily reflect the views or policies of The World Financial Review.