inductively coupled plasma mass spectrometry

inductively coupled plasma mass spectrometry
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Name	Inductively coupled plasma mass spectrometry
Acronyms	ICP-MS
Manufacturers	PerkinElmer, Thermo Fisher Scientific, Agilent Technologies
Uses	Trace elemental analysis, isotopic ratio measurement

inductively coupled plasma mass spectrometry

Inductively coupled plasma mass spectrometry is an analytical technique for trace element and isotopic analysis that couples an inductively coupled plasma source with a mass spectrometer. It provides high sensitivity, multi-element capability, and wide dynamic range, enabling applications across environmental monitoring, clinical diagnostics, geochemistry, and materials science. Major commercial platforms are produced by PerkinElmer, Thermo Fisher Scientific, and Agilent Technologies, and the method is widely standardized by organizations such as International Organization for Standardization and United States Environmental Protection Agency.

Introduction

ICP-MS combines plasma generation, ion optics, mass analysis, and detection to quantify elements from parts-per-trillion to percent levels. Pioneering developments occurred alongside work at institutions like Los Alamos National Laboratory, Oak Ridge National Laboratory, and companies including Varian that helped translate research into routine instrumentation. ICP-MS sits alongside techniques such as atomic absorption spectroscopy, inductively coupled plasma optical emission spectrometry, and thermal ionization mass spectrometry within analytical laboratories at universities such as Massachusetts Institute of Technology and Stanford University.

Instrumentation and Components

Typical ICP-MS instruments comprise a plasma source, sample introduction system, interface cones, ion optics, a mass analyzer, and detectors. Manufacturers like Agilent Technologies and Thermo Fisher Scientific integrate collision/reaction cells and vacuum systems inspired by designs from European Organization for Nuclear Research engineers. Ancillary systems include autosamplers from Gilson (company) or Elemental Scientific and software suites influenced by laboratory information management systems at institutions such as National Institutes of Health and Centers for Disease Control and Prevention.

Principles of Operation

An argon plasma, sustained by radiofrequency power generated by systems similar to transmitters by General Electric, atomizes and ionizes sample constituents. Ions extracted through sampler and skimmer cones enter ion optics that focus beams into mass separation devices. The physics draws on work by figures associated with Lawrence Berkeley National Laboratory and techniques paralleling developments at Bell Labs. Charge-to-mass discrimination is performed by mass analyzers which route ions to detectors developed with contributions from companies like Hamamatsu.

Sample Introduction and Ionization

Liquid samples are typically introduced as aerosols via nebulizers and desolvators, components available from T. R. Miller and Meinhard (company), or using laser ablation systems from Teledyne CETAC Technologies for solids. Sample matrices encountered in laboratories at University of Oxford or ETH Zurich require matrix matching or digestion protocols that echo methods from United States Geological Survey and Environmental Protection Agency guidance. The high-temperature plasma (~6000–10000 K) effectively ionizes most elements, a principle exploited in work at Argonne National Laboratory.

Mass Analyzers and Detection

Common mass analyzers include quadrupole, sector field, and time-of-flight configurations, each implemented by vendors like Thermo Fisher Scientific (sector field), Agilent Technologies (quadrupole), and Tofwerk (time-of-flight). Detectors such as electron multipliers and Faraday cups, designs refined at Rutherford Appleton Laboratory and Max Planck Society institutes, convert ion currents into measurable signals. Hybrid systems integrate collision/reaction cells—concepts advanced in collaborations involving Lawrence Livermore National Laboratory—to reduce polyatomic interferences.

Calibration, Quantification, and Data Reduction

Quantification commonly uses external calibration with standards from producers like National Institute of Standards and Technology or internal standardization employing isotopes such as those studied at Scripps Institution of Oceanography. Methods include standard addition, isotope dilution, and use of certified reference materials from International Atomic Energy Agency. Data reduction workflows are implemented in software linked to laboratory systems at European Commission reference labs and follow guidelines from bodies like ASTM International.

Applications and Examples

ICP-MS is used for trace metals in drinking water monitoring programs run by United States Environmental Protection Agency, clinical assays in facilities such as Mayo Clinic, isotope geochemistry at Scripps Institution of Oceanography and University of Cambridge, and semiconductor impurity analysis at fabs operated by Intel and Samsung Electronics. Forensic laboratories at agencies like Federal Bureau of Investigation employ ICP-MS for elemental profiling, while art conservation studies at museums like the British Museum use laser ablation ICP-MS for provenance investigations.

Limitations, Interferences, and Quality Control

Common limitations include matrix-induced signal suppression, isobaric and polyatomic interferences, and spectral overlaps addressed by collision/reaction cell strategies developed with input from Paul Scherrer Institute. Quality control relies on blanks, duplicates, spiked recoveries, and participation in interlaboratory comparisons coordinated by Interlaboratory Study Program and proficiency testing by organizations like World Health Organization. Instrument maintenance and calibration traceable to National Institute of Standards and Technology standards mitigate drift and ensure comparability.

Category:Analytical chemistry instruments