Inductively Coupled Plasma-Mass Spectrometry - Basics Principle


Inductively Coupled Plasma-Mass Spectrometry




Inductively coupled plasma mass spectrometry (ICP-MS) is a type of mass spectrometry that is capable of detecting metals and several non-metals at concentrations as low as one part in 1012 (part per trillion). This is achieved by ionizing the sample with inductively coupled plasma and then using a mass spectrometer to separate and quantify those ions. Compared to atomic absorption techniques, ICP-MS has greater speed, precision, and sensitivity. However, analysis by ICP-MS is also more susceptible to trace contaminants from glassware and reagents. In addition, the presence of some ions can interfere with the detection of other ions. The variety of applications exceeds that of ICP-OES and includes isotopic speciation. Due to possible applications in nuclear technologies, ICP-MS hardware is a subject for special exporting regulations.

Inductively coupled plasma

An inductively coupled plasma is a plasma that is energized (ionized) by inductively heating the gas with an electrical coil, and contains a sufficient concentration of ions and electrons to make the gas electrically conductive. Even a partially ionized gas in which as little as 1% of the particles are ionized can have the characteristics of a plasma (i.e., response to magnetic fields and high electrical conductivity).[citation needed] The plasmas used in spectrochemical analysis are essentially electrically neutral, with each positive charge on an ion balanced by a free electron. In these plasmas the positive ions are almost all singly charged and there are few negative ions, so there are nearly equal amounts of ions and electrons in each unit volume of plasma.

An inductively coupled plasma (ICP) for spectrometry is sustained in a torch that consists of three concentric tubes, usually made ofquartz. The end of this torch is placed inside an induction coil supplied with a radio-frequency electric current. A flow of argon gas (usually 14 to 18 liters per minute) is introduced between the two outermost tubes of the torch and an electric spark is applied for a short time to introduce free electrons into the gas stream. These electrons interact with the radio-frequency magnetic field of the induction coil and are accelerated first in one direction, then the other, as the field changes at high frequency (usually 27.12 million cycles per second). The accelerated electrons collide with argon atoms, and sometimes a collision causes an argon atom to part with one of its electrons. The released electron is in turn accelerated by the rapidly changing magnetic field. The process continues until the rate of release of new electrons in collisions is balanced by the rate of recombination of electrons with argon ions (atoms that have lost an electron). This produces a ‘fireball’ that consists mostly of argon atoms with a rather small fraction of free electrons and argon ions. The temperature of the plasma is very high, of the order of 10,000 K.

The ICP can be retained in the quartz torch because the flow of gas between the two outermost tubes keeps the plasma away from the walls of the torch. A second flow of argon (around 1 liter per minute) is usually introduced between the central tube and the intermediate tube to keep the plasma away from the end of the central tube. A third flow (again usually around 1 liter per minute) of gas is introduced into the central tube of the torch. This gas flow passes through the centre of the plasma, where it forms a channel that is cooler than the surrounding plasma but still much hotter than a chemical flame. Samples to be analyzed are introduced into this central channel, usually as a mist of liquid formed by passing the liquid sample into a nebulizer. As a droplet of nebulized sample enters the central channel of the ICP, it evaporates and any solids that were dissolved in the liquid vaporize and then break down into atoms. At the temperatures prevailing in the plasma a significant proportion of the atoms of many chemical elements are ionized, each atom losing its most loosely bound electron to form a singly charged ion.

Mass spectrometry

For coupling to mass spectrometry, the ions from the plasma are extracted through a series of cones into a mass spectrometer, usually a quadrupole. The ions are separated on the basis of their mass-to-charge ratio and a detector receives an ion signal proportional to the concentration. The concentration of a sample can be determined through calibration with certified reference material such as single or multi-element reference standards. ICP-MS also lends itself to quantitative determinations through isotope dilution, a single point method based on an isotopically enriched standard. Other mass analyzers coupled to ICP systems include double-focusing magnetic-electrostatic sector systems with both single and multiple collectors, as well as the time of flight systems (both axial and orthogonal accelerators have been used).

Source: Wikipedia

Comments

Post a Comment

Popular posts from this blog

Rare-Earth Elements and Geopolitical Concerns

Image
  Rare-Earth Elements and Geopolitical Concerns Rare-earth elements (REE) are a group of seventeen chemical elements in the periodic table, the fifteen lanthanides as well as yttrium and scandium as defined by the International Union of Pure and Applied Chemistry (IUPAC). Scandium and yttrium are considered REE since they tend to occur in the same ore deposits as the lanthanides and exhibit similar chemical properties.  The REE geochemical classification is usually done on the basis of their atomic weight. One of the most common classifications divides REE into 3 groups: light rare earths elements (LREE - from 57La to 60Nd), intermediate (MREE - from 62Sm to 67Ho) and heavy (HREE - from 68Er to 71Lu). REE usually appear as trivalent ions, except for Ce and Eu which can take the form of Ce4+ and Eu2+ depending on the redox conditions of the system. In lanthanide atoms, the configuration of the valence electrons of the outermost shell is the same for all the species while the 4f...
Read more

Inductively Coupled Plasma-Mass Spectrometry

Image
  Inductively Coupled Plasma-Mass Spectrometry Inductively coupled plasma mass spectrometry (ICP-MS) is a type of mass spectrometry that is capable of detecting metals and several non-metals at concentrations as low as one part in 1012 (part per trillion). This is achieved by ionizing the sample with inductively coupled plasma and then using a mass spectrometer to separate and quantify those ions. Inductively coupled plasma is the plasma that is energized by inductively heating the argon gas with an electrical coil and contains a sufficient concentration of ions and electrons to make the gas electrically conductive. A number of different ICP-MS designs are commercially available today and share similar components such as the nebulizer, spray chamber, plasma torch, interface, and detector.  The liquid sample is pumped into a nebulizer where it is converted into a fine aerosol with argon gas. The fine droplets (1-2%) are separated from larger droplets using a spray chamber. The ...
Read more

Inductively Coupled Plasma Mass Spectrometry (ICP-MS) systems

Image
    Inductively Coupled Plasma Mass Spectrometry (ICP-MS) Inductively Coupled Plasma Mass Spectrometry (ICP-MS) systems are redefining precision in chemical analysis. These advanced instruments enable ultra-trace detection of metals and non-metals in various samples, making them indispensable in fields like environmental testing, pharmaceuticals, food safety, and materials science. With exceptional sensitivity and a wide dynamic range, ICP-MS systems support industries striving for regulatory compliance and enhanced quality control. As analytical needs become increasingly complex, the versatility of ICP-MS systems stands out. Their ability to perform multi-element analysis and isotopic studies in a single run saves time and resources. From identifying contaminants in drinking water to ensuring the purity of pharmaceutical products, ICP-MS systems empower researchers and industries with accurate, reliable data. Innovations such as collision/reaction cell technology further enha...
Read more