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Please see our Inductively Coupled Plasma Mass Spectrometer (ICP MS) section to find manufacturers that sell these products
Inductively coupled plasma-mass spectrometry (ICP-MS) is a type of mass spectrometry for measuring most of the elements in the periodic table with detection limits at or below the parts-per-trillion range. Most samples analyzed by ICP-MS systems are liquids. However, solid samples can also be analyzed after vaporization, and gas samples can be measured by direct introduction into the instrument. Over the years, ICP-MS has become the technique of choice for both routine analyses and research in a variety of areas.
There are several ICP-MS systems to choose from, depending on the specific applications.
ICP-MS methods
An ICP-MS system consists of the following components: a nebulizer, ICP torch, interface region, vacuum region, lens system, mass spectrometer, vacuum system, detector, and data handling system.
The sample is introduced into the ICP plasma as an aerosol, by aspirating a liquid or dissolved solid sample into a nebulizer, or using a laser to directly convert solid samples into an aerosol.
The ICP torch is a series of concentric quartz tubes wrapped with a radiofrequency (RF) coil. Plasma is formed in the ICP torch by passing argon through the ICP torch and bringing the argon in contact with energy supplied to the RF coil. The liquid droplets are introduced into the plasma and are heated to a gas. Atoms are generated from the gas and travel through the plasma. As they travel through the plasma, they absorb energy and turn into ions.
The ions exit the plasma into the interface region, which maintains the composition and integrity of the ions, and then pass into the region of the lens system through the vacuum region.
The lens system can have one or more lenses and electrostatically steer the maximum number of ions from the sampling region, while minimizing the transport of unwanted components.
The vacuum system focuses the ions into the detector. The detector separates the ions on the basis of mass-to-charge ratio. An electronic signal is generated and analyzed by the data handling system.
Data analysis
The ICP-MS system requires calibration and can provide data using semiquantitative, quantitative, isotope dilution, and isotope ratio analysis.
Semiquantitative analysis provides a fingerprint of the elements present in a sample and can help determine the standards for quantitative analysis and the presence of interfering elements.
In quantitative analysis, the ICP-MS system determines the concentration of a specific element in the sample by comparing the counts measured for a selected isotope to an external calibration curve.
In isotope ratio measurements, the ICP-MS system measures specific isotopes of an element, and the isotope ratio of two or more isotopes can readily be determined.
In isotope dilution measurements, the sample is spiked with an enriched isotope of the element of interest. The enriched isotope acts as both a calibration standard and an internal standard.
ICP-MS systems purchasing considerations
The process of selecting an ICP-MS system is complicated, and the prospective purchaser should consider the following:
Applications
An important consideration in selecting an ICP-MS system is its area of application.
The NexION® 350Q ICP-MS from PerkinElmer is suitable for routine applications requiring high throughput that have few interferences, and is designed for geochemical laboratories.
The PerkinElmer NexION 350S ICP-MS is for applications requiring a high level of interference removal, and is designed for the semiconductor industry.
The 8800 ICP-QQQ from Agilent Technologies is well suited for ultratrace analysis in high-purity semiconductor applications.
The ELEMENT 2™ ICP-MS from Thermo Fisher Scientific is suitable for the analysis of trace elements with application from geological and environmental analyses and biological research to material sciences.
Thermo Fisher Scientific offers the iCAP Qa for routine analysis, iCAP Qc for high-sensitivity measurement, and iCAP Qs for research applications.
Resolution
Another important factor to consider is the resolution of the ICP-MS system, which depends on the choice of mass analyzer. There are three types of mass analyzers: quadrupole, high resolution, and multicollector high resolution.
The quadrupole mass spectrometer is most commonly used and works by allowing only one mass to pass through to the detector and sorts the ions based on mass-to-charge ratio. The quadrupole mass spectrometer has adequate resolution for most routine applications.
The 8800 ICP-QQQ and 7700s ICP-MS from Agilent Technologies rely on a quadrupole mass analyzer.
In instances where the resolution of the quadrupole mass analyzer is not adequate, high-resolution mass analyzers eliminate or reduce the effects of these interferences. High-resolution ICP-MS (HR-ICP-MS) systems operate at preset resolution settings for low, medium, or high resolution.
The ELEMENT XR™ and ELEMENT 2™ from Thermo Fisher Scientific are HR-ICP-MS systems.
A second type of HR-ICP-MS is the multicollector high-resolution ICP-MS (MC-HR-ICP-MS) system, which is generally designed for high-precision isotope ratio analyses and is equipped with an array of 5-10 detectors and a double-focusing system.
The NEPTUNE Plus from Thermo Fisher Scientific is an MC-HR-ICP-MS that is suitable for high-precision isotope ratio measurements in earth science and nuclear science applications.
HR-ICP-MS and MC-HR-ICP-MS cost significantly more than quadrupole ICP-MS systems and are more complex to operate and maintain. MC-HR-ICP-MS are generally not suitable for routine applications.
Dynamic range
Another important consideration in selecting an ICP-MS system is its dynamic range, which is determined by the choice of detector.
The 7900 ICP-MS from Agilent Technologies is equipped with an orthogonal detector system that delivers up to 11 orders of magnitude dynamic range from sub-parts-per-trillion to percent-level concentrations.
Optical system
An important consideration in selecting an ICP-MS system is the optical system, which is designed to work with the interface and mass spectrometer design of the ICP-MS.
The 8800 ICP-QQQ from Agilent Technologies features a dual conical extraction and off-axis Omega lens.
The 7700s ICP-MS from Agilent offers an off-axis ion lens.
The SPECTRO MS ICP-MS from SPECTRO Analytical Instruments Inc. has an ion optic system and a double-focusing sector field mass spectrometer for measuring the complete mass range used for inorganic mass spectrometry from 6Li to 238U with a permanent ion beam going to the detector.
Data handling system
Another key consideration is the ability to control the ICP-MS system. Most data handling systems provide remote monitoring, quality control, optimization, and data handling and calculation. Additional features are described below.
ICP-MS MassHunter Workstation Software from Agilent Technologies, for the 7700 Series, 8800 ICP-QQQ, and 7900 ICP-MS, is designed to work with Apple or Android devices.
Syngistix™ software from PerkinElmer for the NexION 350 ICP-MS features a dedicated Nano Application Module for nano- material applications.
Customization options
The availability of customization options should be taken into account as well.
The 7700x ICP-MS from Agilent comes with options for chromatographic coupling, analysis of organic solvents, and highly corrosive acids.
The aurora M90 from Bruker has an option to inject helium and hydrogen to the plasma. The aurora M90 nitrox 500 accessory allows online addition of nitrogen or oxygen gas to the plasma.
Table 1 – Providers of ICP-MS systems
Representative ICP-MS systems
Agilent Technologies: 7900 ICP-MS, 8800 ICP-QQQ, 7700 ICP-MS Series (7700x ICP-MS, 7700s ICP-MS, 7700e ICP-MS)
Bruker: aurora M90, aurora Elite
Nu Instruments Ltd.: AttoM®
PerkinElmer: NexION 350 ICP-MS
SPECTRO Analytical Instruments Inc.: SPECTRO MS ICP-MS
Thermo Fisher Scientific: ELEMENT 2 ICP-MS, ELEMENT XR ICP-MS, iCAP Q ICP-MS (iCAP Qa, , iCAP Qc), Neptune
U-Therm International (H.K.) Ltd.: ICP-TY-9900, ICP-TY-9920
Recent ICP-MS development
ICP-MS has been adapted to blend flow cytometry and mass spectrometry with essentially the same workflow as flow cytometry. The resulting system is referred to as a “mass cytometer” and offers an attractive alternative to flow cytometry. The first commercial mass cytometer, the CyTOF® 2 Instrument, is available from DVS Sciences (www.dvssciences.com).
Providers
A list of providers of ICP-MS systems is given in Table 1.
Please see our Inductively Coupled Plasma Mass Spectrometer (ICP MS) section to find manufacturers that sell these products