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Inductively coupled plasma - Optical emission spectroscopy: A review

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Asian J. Pharm. Ana. 2013; Vol. 3: Issue 1, Pg 24-33 [AJPAna.]

ISSN- 2231–5667 (Print) www.asianpharmaonline.org

ISSN- 2231–5675 (Online)

REVIEW ARTICLE

Inductively Coupled Plasma –Optical Emission Spectroscopy: A Review.

Somsubhra Ghosh1*, V. Laxmi Prasanna1, B. Sowjanya1, P. Srivani1, M. Alagaraja1, Dr. David
Banji1
Nalanda College of Pharmacy, Nalgonda, Andhra Pradesh – 508001, India
*Corresponding Author E-mail: somsubhraghosh@gmail.com

ABSTRACT:
Spectroscopy is the chief experimental technique of atomic and molecular physics and involves determining the energy
states of atoms or molecules by looking at the light absorbed or emitted when they change states. Measuring the
frequency of light absorbed or emitted which is determined by the energy difference between the two states, can
provide a sensitive probe of interactions which perturb those energy states. Among those in this review we revealed
that the principle, instrumentation and applications of inductively coupled plasma optical emission spectroscopy. In
this sample is usually transported into the instrument as a stream of liquid sample. Inside the instrument, the liquid is
converted into an aerosol through a process known as nebulisation. The sample aerosol is then transported to the
plasma where it is desolvated, vaporized, atomized, and excited and/or ionized by the plasma. The excited atoms and
ions emit their characteristic radiation which is collected by a device that sorts the radiation by wavelength. The
radiation is detected and turned into electronic signals that are converted into concentration information for the analyst.

KEYWORDS: Spectroscopy , nebulisation, desolvation, plasma

INTRODUCTION:
Inductively coupled plasma/optical emission spectroscopy Principle:
(ICP/OES) is a powerful tool for the determination of The principle used in the inductively coupled Plasma
metals in a variety of different sample matrices. With this Optical Emission Spectroscopy is When plasma energy is
technique, liquid samples are injected into a radiofrequency given to an analysis sample from outside, the component
(RF)-induced argon plasma using one of a variety of elements (atoms) are excited.(3) When the excited atoms
nebulizers or sample introduction techniques (1). The return to low energy position, emission rays (spectrum
sample mist reaching the plasma is quickly dried, rays) are released and the emission rays that correspond to
vaporized, and energized through collisional excitation at the photon wavelength are measured. The element type is
high temperature. The atomic emission emanating from the determined based on the position of the photon rays, and
plasma is viewed, collected with a lens or mirror, and the content of each element is determined based on the rays
imaged onto the entrance slit of a wavelength selection intensity(4). To generate plasma, first, argon gas is supplied
device. Single element measurements can be performed to torch coil, and high frequency electric current is applied
cost effectively with a simple monochromator/ to the work coil at the tip of the torch tube. Using the
photomultiplier tube (PMT) combination, and simultaneous electromagnetic field created in the torch tube by the high
multielement determinations are performed for up to 70 frequency current, argon gas is ionized and plasma is
elements with the combination of a polychromator and an generated. This plasma has high electron density and
array detector.(2) The analytical performance of such temperature (10000K) and this energy is used in the
systems is competitive with most other inorganic analysis excitation-emission of the sample. Solution samples are
techniques, especially with regards to sample throughput introduced into the plasma in an atomized state through the
and sensitivity. narrow tube in the center of the torch tube(5).
Inductively Coupled Plasma Characteristics:
The main analytical advantages of the ICP over other
excitation sources originate from its capability for efficient
Received on 22.12.2012 Accepted on 25.01.2013
and reproducible vaporization, atomization, excitation, and
© Asian Pharma Press All Right Reserved
Asian J. Pharm. Ana. 3(1): Jan.-Mar. 2013; Page 24-33
ionization for a wide range of elements in various sample

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Asian J. Pharm. Ana. 2013; Vol. 3: Issue 1, Pg 24-33 [AJPAna.]

matrices. This is mainly due to the high temperature, 6000– Sample introduction
7000 K, in the observation zones of the ICP.(5)This (1) Nebulizers:
temperature is much higher than the maximum temperature Nebulizers are devices that convert a liquid into an aerosol
of furnaces (3300 K). The high temperature of the ICP that can be transported to the plasma. The nebulization
also makes it capable of exciting refractory elements, and process is one of the critical steps in ICP-OES. The ideal
renders it less prone to matrix interferences. Other sample introduction system would be one that delivers all
electrical-discharge-based sources, such as alternating of the sample to the plasma in a form that the plasma could
current and direct current arcs and sparks, and the MIP, reproducibly desolvate, vaporize, atomize and ionize, and
also have high temperatures for excitation and ionization, excite. Because only small droplets are useful in the ICP,
but the ICP is typically less noisy and better able to handle the ability to produce small droplets for a wide variety of
liquid samples. In addition, the ICP is an electrode less samples largely determines the utility of a nebulizer for
source, so there is no contamination from the impurities ICP-OES. (3)
present in an electrode material the following is a list of
some beneficial characteristics of the ICP source. Many forces can be used to break up a liquid into an
• high temperature (7000–8000 K) aerosol; however, only two have been used successfully
• high electron density (1014–1016cm3) with an ICP, pneumatic forces and ultrasonic mechanical
• Appreciable degree of ionization for many elements forces .
simultaneous multi element capability (over 70
elements including P and S) Pneumatic nebulizer:
• Low background emission, and relatively low Ex:Babington nebulizer
chemical interference
• High stability leading to excellent accuracy and precision Babington nebulizer:
• Excellent detection limits for most elements (0.1 –100 The Babington nebulizer, shown in Figure No: 2 works by
ng mL1) allowing the liquid to flow over a smooth surface with a
small hole in it. High-speed argon gas emanating from the
• Wide linear dynamic range (LDR) (four to six orders
hole shears the sheet of liquid into small drops.
of magnitude)
• Cost-effective analyses.
Instrumentation:
In inductively coupled plasma-optical emission
spectrometry, the sample is usually transported into the
instrument as a stream of liquid sample. Inside the
instrument, the liquid is converted into an aerosol through a
process known as nebulisation. (1) The sample aerosol is
then transported to the plasma where it is desolvated,
vaporized, atomized, and excited and/or ionized by the
plasma. The excited atoms and ions emit their
characteristic radiation which is collected by a device that
sorts the radiation by wavelength.(2) The radiation is
Figure No.2: Shows Babington nebulizer
detected and turned into electronic signals that are
converted into concentration information for the analyst. A
This nebulizer is susceptible to clogging and can be used
representation of the layout of a typical ICP-OES
for the viscous liquids.
instrument is shown in Figure No 1.
Ultrasonic nebulizer
In ultrasonic nebulisation, liquid sample is pumped onto an
oscillating piezoelectric transducer. The oscillations break
the sample into a fine aerosol, so aerosol formation is
independent of nebulizer gas flow.

More sample will reach the ICP, providing detection limits

which are usually 10 times lower than pneumatic
nebulization. The higher efficiency of the ultrasonic
nebulizer increases the water load to the ICP, so a
desolvation unit is added after the nebulizer. The cooling
portion of the desolvation unit has been replaced, in some
commercially available systems, with a Peltier cooling
device. However, the ultrasonic nebulizer is still
Figure No 1: Shows the major components and layout of a typical susceptible to matrix effects, high solids loading and is not
ICP-OES instrument. HF resistant.(4)
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Asian J. Pharm. Ana. 2013; Vol. 3: Issue 1, Pg 24-33 [AJPAna.]

Figure No.3 Ultrasonic nebulizer with desolvation unit

Pumps: Spray chambers:

Once the sample aerosol is created by the nebulizer, it must
be transported to the torch so it can be injected into the
plasma. Because only very small droplets in the aerosol are
suitable for injection into the plasma, a spray chamber is
placed between the nebulizer and the torch. Some typical
ICP spray chamber designs are shown in Figure no.5. The
primary function of the spray chamber is to remove large
droplets from the aerosol. A secondary purpose of the
spray chamber is to smooth out pulses that occur during
nebulisation.In general, spray chambers for the ICP are
designed to allow droplets with diameters of about 10 m or
smaller to pass to the plasma. With typical nebulizers, this
droplet range constitutes about 1 - 5% of the sample that is
introduced to the nebulizer. The remaining 95 - 99% of the
sample is drained into a waste container. The material from
Figure No.4: Peristaltic pump used for ICP-OES. which a spray chamber is constructed can be an important
characteristic of a spray chamber. Spray chambers made
Babington and Ultrasonic nebulizer require the solution to from corrosion-resistant materials allow to introduce
be pumped into the nebulizer, where as some of the samples containing hydrofluoric acid which could damage
(6)
nebulizers like concentric and cross-flow nebulizers can glass spray chambers.
naturally draw the solution into the nebulizer by a process
known as aspiration, a pumped flow is useful for these
nebulizers also. With a pumped solution, the flow rate of
the solution into the nebulizer is fixed and is not dependent
on solution parameters such as viscosity and surface
tension. The controlled flow rate of liquid also allows for
more rapid washout of the nebulizer and spray chamber.
Peristaltic pumps, such as the one shown in Figure 4, are
almost exclusively the pumps of choice for ICP-OES
applications. These pumps utilize a series of rollers that Figure No.5. Typical spray chamber used with ICP-OES.- Scott
double pass type
push the sample solution through the tubing using a process
known as peristalsis. The pump itself does not come in
Drains: The drain carries excess sample from the spray
contact with the solution, only with the tubing that carries
(3,5) chamber to a waste container can have an impact on the
the solution from the sample vessel to the nebulizer. The
performance of the ICP instrument. Besides carrying away
special tubing used with a peristaltic pump must be
excess sample, the drain system provides the backpressure
compatible with the sample that is passing through it. Most
necessary to force the sample aerosol-carrying nebulizer
types of peristaltic pump tubing are compatible with
gas flow through the torch’s injector tube and into the
weakly acidified aqueous media. Pumping strongly acidic
plasma discharge. If the drain system does not drain evenly
solutions or organic solvents, however, usually requires the
or if it allows bubbles to pass through it, the injection of
use of tubing made of specific materials.
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Asian J. Pharm. Ana. 2013; Vol. 3: Issue 1, Pg 24-33 [AJPAna.]

sample into the plasma may be disrupted and noisy variety of injector tubes. Such injectors include corrosion-
emission signals can result. resistant ceramic injectors, narrow-bore injectors for
analyses involving organic solvents, and wide-bore
Drains for ICP-OES sample introduction systems come in injectors for introducing samples with high dissolved solids
many forms----loops, blocks, U-tubes, or even tubing contents. (9)
connected to a peristaltic pump. For proper performance, it
is important to keep the liquid level within the drain system
at the recommended position. Also, when introducing
organic-based samples into the ICP, it may be necessary to
use drain tubing designated for use with organic solvents.(6)

3.2 .production of emission:

Torches: As shown schematically in Figure no.6, the
torches contain three concentric tubes for argon flow and
aerosol injection. The spacing between the two outer tubes
is kept narrow so that the gas introduced between them
emerges at high velocity. This outside chamber is also
designed to make the gas spiral tangentially around the
chamber as it proceeds upward. One of the functions of this
gas is to keep the quartz walls of the torch cool and thus
this gas flow was originally called the coolant flow or
plasma flow but is now called the "outer" gas flow. For
argon ICPs, the outer gas flow is usually about 7 - 15 litres
per minute. The chamber between the outer flow and the
inner flow sends gas directly under the plasma toroid. This Figure No.7. One-piece ICP torch.
flow keeps the plasma discharge away from the
intermediate and injector tubes and makes sample aerosol
introduction into the plasma easier. In normal operation of
the torch, this flow, formerly called the auxiliary flow but
now the intermediate gas flow, is about 1.0 L/min. The
intermediate flow is usually introduced to reduce carbon
formation on the tip of the injector tube when organic
samples are being analyzed.

(A) (B)
Figure No.8. Demountable ICP Torch. A - expanded view, B -
assembled view.

Radio Frequency Generators: The radio frequency (RF)

generator is the device that provides the power for the
generation and sustainment of the plasma discharge. This
power ranging from about 700 to 1500 watts, is transferred
Figure No. 6. Schematic of a torch used for ICP-OES. to the plasma gas through a load coil surrounding the top of
the torch. The load coil, which acts as an antenna to
transfer the RF power to the plasma, is usually made from
At present, the most popular torches are of the copper tubing and is cooled by water or gas during
demountable type such as the one shown in Figure No.8. operation.
These torches can be taken apart so that the tubes can be
modified or replaced without replacing the entire torch.
The main advantages of the demountable torch lie in the
lower torch replacement costs and the ability to use a
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Asian J. Pharm. Ana. 2013; Vol. 3: Issue 1, Pg 24-33 [AJPAna.]

Most RF generators used for ICP-OES operate at a • Diffraction gratings

frequency between 27 and 56 MHz. The specific frequency • Prisms
used for an ICP-OES instrument is partially determined by • Filters
those frequencies that the U. S. Federal Communications A reflection diffraction grating is simply a mirror with
Commission (FCC) and similar agencies worldwide have closely spaced lines ruled or etched into its surface. Most
designated for scientific and industrial use. Earlier most ofgratings used in ICP-OES instruments have a line, or
the ICP generators were operated at 27.12 MHz. However, groove, density from 600 to 4200 lines per millimetre.
an increasing number of instruments now operate at 40.68 When light strikes such a grating, it is diffracted at an angle
MHz because of improvements in coupling efficiency and that is dependent on the wavelength of the light and the line
reductions in background emission intensity realized at this density of the grating. In general, the longer the wavelength
frequency. Frequencies greater than 40 MHz also have and the higher the line density, the higher the angle of
been used but have not been as successful commercially. diffraction will be. Figure 11 shows schematically the paths
that light rays of two different wavelengths would take
There are two general types of RF generators used in ICP when diffracted from a grating. (11, 12)
instruments. Crystal-controlled generators use a
piezoelectric quartz crystal to produce an RF oscillating To separate polychromatic light the grating is incorporated
signal that is amplified by the generator. in an optical instrument called a spectrometer. The function
of the spectrometer is to form the light into a well-defined
3.3 .Collection and detection of emission beam, disperse it according to wavelength with a grating,
Transfer Optics: and focus the dispersed light onto an exit plane or circle. In
The emission radiation from the region of the plasma other words, the spectrometer receives white light or
known as the normal analytical zone (NAZ) is sampled for polychromatic radiation and disperses it into
the spectrometric measurement. The analytical zone was monochromatic radiation. One or more exit slits on the exit
observed from the side of the plasma operating in a vertical plane or circle are then used to allow certain wavelengths
orientation as shown. to pass to the detector while blocking out other
wavelengths. (13)

Figure No.9.Side-on ICP Viewing.

Figure No.11. shows Diffraction grating separating two

wavelengths of light.

The monochromatic radiation which is diffracted from the

grating is composed primarily of wavelengths
representative of the light emitted by a particular elemental
or molecular species in the ICP.
Figure No.10. End-on ICP Viewing
Poly chromators:
This classical approach to ICP spectroscopy is referred to
as a radial or side-on viewing of the plasma. Whatever the
ICP viewing, the radiation is usually collected by a
focusing optic such as a convex lens or a concave mirror.
This optic then focuses the image of the plasma onto the
entrance slit of the wavelength dispersing device or
spectrometer. (10)

Wavelength Dispersive Devices: The next step in ICP-

OES is the differentiation of the emission radiation from
one element from the radiation emitted by other elements
and molecules. The physical dispersion of the different
Figure No.12. Paschen-Runge mounts used in a Rowland circle
wavelengths is done by polychromator.
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Figure No.13. Czerny-Turner (a) and Ebert (b) monochromator mounts

With polychromators, each emission line can be observed Photo multiplier tube:
during the entire sample introduction period, and The PMT is a vacuum tube that contains a photosensitive
theoretically more samples can be analyzed in a shorter material, called the photocathode that ejects electrons when
period of time. The same amount of time is required to it is struck by light. These ejected electrons are accelerated
determine five elements as it does thirty. Thus, towards a dynode which ejects two to five secondary
polychromators have a high sample throughput rate. Most electrons for every one electron which strikes its surface.
polychromators are programmed for 20 to 30 spectral lines. (14) The secondary electrons strike another dynode, ejecting
more electrons which strike yet another dynode, causing a
Since the spectral line array for polychromators is fixed, multiplicative effect along the way. Typical PMTs contain
spectral interference corrections may be applied to the 9 to 16 dynode stages. The final step is the collection of the
analyte only if a spectral line for the element that is doing secondary electrons from the last dynode by the anode. As
the interfering is included on the array. many as 106 secondary electrons may be collected as the
result of a single photon striking the photocathode of a
Monochromators: nine-dynode PMT. The electrical current measured at the
The most important advantage of monochromator-based anode is then used as a relative measure of the intensity of
systems is their spectral flexibility. By this we mean the the radiation reaching the PMT(17).
ability to access, at any time, any wavelength within the
range of the monochromator. Clearly, the spectral
flexibility of a monochromator-based ICP-OES instrument
allows for the determination of any element whose
emission can be measured by the technique. Because of
their scanning capability, monochromator-based
instruments are much better suited for application of the
complex background correction techniques often necessary
for ICP-OES. Scanning the region around the analyte line
or simultaneously measuring the immediate vicinity of the
line assists in validating the analytical result.
Monochromators require large amounts of sample and have
a lower sample throughput than polychromator systems.(15)

Detectors:
Once the proper emission line has been isolated by the
spectrometer, the detector and its associated electronics are
used to measure the intensity of the emission line.
Most commonly used detectors are(16)

Photo multiplier tube

Array detectors

Photodiode array

Charge-injection device (CID)
Figure No.14 shows schematically how a PMT amplifies the signal

Charge-coupled device (CCD)
produced by a photon striking a photocathode.

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Asian J. Pharm. Ana. 2013; Vol. 3: Issue 1, Pg 24-33 [AJPAna.]

The major advantages of the PMT over other detection blaze wavelength, and for a particularly order which is
devices are that it can be used to measure light over a usually the first order. Secondly, the system has excellent
relatively wide wavelength range, it can amplify very weak resolution since it is generally used in the higher spectral
emission levels, and its range of response can be extended orders. (Resolution enhancements are exhibited with
to over nine orders of magnitude in light intensity. increasing order.) Because of the use of higher orders with
Photocathode, dynode and anode layout of a better resolution, the physical size of the instrument may be
photomultiplier tube. Diffraction grating, there is another reduced thus producing a small instrument footprint. (18)
optical component, the prism, which disperses
polychromatic radiation into its characteristic wavelengths. Advanced Array Detectors
In fact, the instrument used by Kirchhoff and Bunsen in the In the 1960s, solid-state devices were introduced into the
early 1860’s to detect the four new elements, Cs, Rb, Tl, electronics industry. These devices, such as transistors and
and In, incorporated a prism to disperse the polychromatic diodes, were based on the properties of silicon but were
radiation from the Bunsen flame into monochromatic relegated to research and aerospace applications that could
radiation. afford the relatively high cost of these components. As
their use expanded to the digital electronics industry in the
In recent years, it has been shown that certain advantages form of integrated circuits (ICs), not only did the cost of
may be obtained by combining the characteristics of two the devices become affordable but the cost of systems
dispersing systems such as a diffraction grating and a prism using the ICs such as digital computers were drastically
or two diffraction gratings. reduced(19).

It was also discovered that silicon-based sensors responded

to light and were quickly integrated into linear and two-
dimensional arrays called solid-state imagers or detectors.
Consequently, three generic, advanced solid-state detectors
with high sensitivity and resolution for spectroscopic
applications have been developed –
• The photodiode array (PDA),
• The charge-injection device (CID)
• The charge-coupled device (CCD).

Figure No.16. Metal Oxide - Silicon (MOS) capacitor.

Figure No 15. An echelle optical mount.

The two optical components are positioned perpendicular

to each other. One of the dispersing devices is, in general,
an echelle grating which is a very course grating in
comparison to the normal diffraction grating. The echelle
grating separates the polychromatic radiation by
wavelengths and produces multiple, overlapping spectral
orders. The second dispersing device, either a grating with
a ruling density greater than 350 gr/mm or a prism,
separates or cross disperses the overlapping orders into a
two dimensional pattern called an echellogram. A typical
optical configuration for this echelle type of spectrometer Figure.No.17. Photon absorption by silicon crystalline lattice and
the formation of electron-hole pairs.
is illustrated in Figure 15.
The CID and CCD devices are based on the light-sensitive
Echelle grating-based spectrometers offer some distinct
properties of solid-state silicon and belong to the broad
advantages over the conventional spectrometers. Firstly,
class of silicon-based devices called charge transfer devices
the optics results in very good efficiency in each of the
(CTD).To illustrate the principals associated with CTDs, a
spectral orders. Conventional diffraction gratings are
block of very high purity crystalline silicon is considered
generally optimized at a particular wavelength, called the
(Figure 16). Onto this silicon substrate is grown an
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Asian J. Pharm. Ana. 2013; Vol. 3: Issue 1, Pg 24-33 [AJPAna.]

insulating layer of silicon dioxide (SiO2). As shown in the

pictorial Figure 17, each silicon atom in the substrate is
bonded to its adjacent silicon atom in a three dimensional
lattice. The silicon-silicon bond may be broken by energy
of sufficient strength such as photons with visible or
ultraviolet wavelength. When the bond is broken, an
electron is released within the lattice structure and a
subsequent hole in the crystalline structure is formed. This
is called an electron-hole pair.

If a voltage is applied across the block of silicon (Figures Figure No.19. SCD Detector Subarray
16 and 17), the freed electrons will move in the opposite
3.4. Signal processing and instrument control
direction of the applied electric field or toward the silicon-
silicon dioxide interface while the holes will move in the Signal Processing
The electronics used for signal processing in ICP-OES
other direction or in the same direction as the electric field
and leave a region depleted of positive charge. This systems utilizing PMT detection are generally straight
electron and hole motion within the crystalline lattice forward. The electrical current measured at the anode of
creates a current which is proportional to the amount of the PMT is converted into information that can be used by
photons impinging on the structure. That is, the more light a computer.22 The first step is to convert the anode current,
absorbed by the silicon, the more electrons are captured at which represents emission intensity, into a voltage signal
the silicon silicon oxide interface. (20) and utilize digital signal processing, the voltage signal is
converted into digital information via an analog-to-digital,
The CTDs elements, called pixels, may vary in size from 6 or A/D, converter. This digital information can then be
to 30 microns and arranged generally in a two-dimensional used by a computer for further processing, the end result
silicon wafer configuration from 512 x 512 to 4096 x 4096 being information passed on to the computer.
pixels. Each of these pixels is capable of storing photon-
generated charge Computers and Processors
An important part of any ICP-OES instrument is the
In general, each pixel of the two-dimensional Charge computer control incorporated into the instrument. The
Injection Devices (CIDs) may be randomly interrogated to majority of automated functions of an ICP-OES instrument
determine the amount of charge that has been accumulated are directly controlled by an on-board computer.At the
during a measured time to which the device has been simplest level of multi element ICP-OES instrumentation, a
exposed to light (called the integration time). With the computer is needed to handle the massive amounts of data
advent of high speed microprocessors, individual pixels that such an instrument generates. While virtually every
may be examined even during the integration time to commercial ICP-OES instrument available today uses
determine the accumulated charge. This process of some type of computer to control the spectrometer and to
examining the contents does not destroy the contents and, collect, manipulate, and report analytical data, the amount
hence, is known as a non-destructive read-out mode. of computer control over other functions of the instrument
However, even though the CID has a random access and varies widely from model to model. (26)
non-destructive read-out, it has an inherently higher noise
level or dark current than, for example, a CCD, and Software
requires cooling to liquid nitrogen temperatures to ICP-OES instrument would be that it could prepare the
effectively decrease this noise. The dark current of any standards and samples, develop the analytical method,
device is the electronic current that flows in a detector analyze the samples, report the results, and make decisions
when operating voltages are applied but no light is present. based on those results all from a single keystroke.
(21)

The objective of a good software package is not only to

control the automated features of the instrument during
collection of analytical data but to simplify the overall
operation of the instrument. Areas in which this is
important include not only running an analysis but
developing analytical methods and reporting results. The
methods development task involves selecting proper
operating parameters for an analysis, such as wavelengths,
PMT voltages, background correction points, and standards
concentrations. The ability to view spectral data displayed
graphically with a minimum of effort is indispensable
during the selection of these parameters.
Figure No.18. Segmented array charge-coupled device detector
(SCD)

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4. ICP-OES Methodology: • The major use of ICP-OES in this field is mainly used
The first step in an analysis is to prepare the samples and for prospecting purposes.
standards for introduction to the ICP. This step depends on • The technique is also used for applications such as
the physical and chemical characteristics of the samples determining origins of rock formations and for marine
and from simple dilution to a complex series of chemical geochemistry.
reactions and other preparation steps. The next step in the • Determination of U in ore grade material.
analysis concerns the sample introduction method and • Analysis of river sediments for several metals.
hardware to be used. For most ICP-OES analyses, the • Analysis of carbonate drill cores for major, minor and
standard sample introduction system provided with the trace elements.
instrument will be sufficient. • Determination of rare earth elements in rock
formations.
The next step in the development of an analysis • Analysis of plankton for several elements.(26)
methodology is to program the instrument, using the
4) Environmental and Waters:
computer software provided with the instrument, to
• Analyses of sewage sludge, domestic and industrial
perform the data collection and processing steps. To do
refuge, coal and coal fly ash, and dust and other airborne
this, decisions must be made concerning the operating
particulates.
conditions, wavelength selection, instrument calibration,
• Various water quality analyses as required by the U.S.
emission measurement, and the actual sample analysis. For
Environmental Protection Agency.
many analyses, the default conditions recommended by the
instrument manufacturer will provide satisfactory results. • Determination of Fe, Cd, Cu, Mo, Ni, V, and Zn in
Once the samples and standards are prepared, the hardware seawater.
is set up properly, and the computer is programmed, the • Determination of phosphorus in municipal wastewater.
analysis may begin. The analyst usually starts by • Determination of heavy metals in inner-city dust
introducing the first standard solution to the plasma and samples.
pressing a key on the computer. Assuming everything is • Trace metal analysis of coal fly ash.
found to be working properly, the analyst continues by 5) Metals:
introducing further standards (if used) and a blank solution • Determination of toxic, trace and major constituents in
to complete the calibration of the instrument. If no other coal and slags.
calibrations or checks are required, the calibration is • Analysis of low alloy steels for As, B, Bi, Ce, La, P,
followed by introduction of samples. Once the analysis of Sn and Ta; high-precision determination of Si in steels;
samples is completed, the results can be tabulated and • Determination of contaminants in high-purity Al.
reported as necessary.(24) • Analysis of superconducting materials for trace
contaminants.(27)
5. Applications:
1) Agricultural and Foods: 6) Organics:
• The ICP-OES technique has been applied to the • Analysis of organic solutions by ICP-OES is
analysis of a large variety of agricultural and food important not only for analyzing organic-based materials
materials. Types of samples include soils, fertilizers, plant such as petroleum products but also for a wide variety of
materials, feedstuffs, foods, animal tissues, and body other applications. (28)
fluids. Analysis of infant formula for Ca, Cu, Fe, Mg, Mn, • The analysis of used lubricating oils for trace metal
P, K, Na and Zn; content is one of the more popular applications for organics
• Determination of trace metals in beer and wine.(25) analysis by ICP-OES. Some other applications include
2) Biological and Clinical: analysis of solvent-extracted geological materials for trace
• The use of surgical equipment, such as scalpels, elemental composition.
needles, scissors, and forceps, often contaminates the • Determination of lead in gasoline;
sample with trace quantities of the very elements being • Determination of Cu, Fe, Ni, P, Si and V in cooking
determined in the sample. oils.
• Determinations of Cr, Ni and Cu in urine. • Analysis of organophosphates for trace contaminants.
• Determination of Al in blood. • Determination of major and trace elements in
• Determination of Cu in brain tissue. antifreeze.(29,30)
• Determination of Se in liver.
• Determination of Ni in breast milk. CONCLUSION:
• Determination of B, P and S in bone. As Inductively coupled plasma-optical emission
• Determination of trace elements in oyster and tuna spectrometry (ICP-OES) is an attractive technique that has
tissues. led many analysts to ask whether it is wiser to buy an ICP-
3) Geological OES or to stay with their trusted atomic absorption
• Determination of major, minor and trace compositions technique (AAS) and one of the sophisticated analytical
of various rocks, soils, sediments, and related materials. techniques used now a days by many pharmaceutical
industries. Being having the vast number of applications in
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 Asian J. Pharm. Ana. 2013; Vol. 3: Issue 1, Pg 24-33 [AJPAna.]

the analysis of the samples of foods, agriculture etc, it is 13. C.B. Boss, K.J. Fredeen, Concept, Instrumentation and
the choice by many analysts. The multielement analysis of Techniques in Inductively Coupled Plasma Optical Emission
Spectrometry, 2nd edition, Perkin-Elmer, Norwalk, CT, 1997.
water is one of the major applications for inductively 14. R.H. Wendt, V.A. Fassel, ‘Induction-coupled Plasma
coupled plasma-optical emission spectroscopy (ICP-OES), Spectrometric Excitation Source’, Anal. Chem., 37(7), 920–922
describes the analysis of metals and trace elements in (1965).
drinking water in terms of sensitivity, precision, and 15. Available at
accuracy. The modern ICP-OES method can success fully http://www.santarosa.edu/~oraola/S09/CHEM5/Spectroscopy
%20 Analysis %20 of %20 Drinking %20 Water %20 Using
be used to assess content and fine the profile of many trace
%20 ICP-OES.pdf.date 21-1-2012, time.11pm
elements in organs and body fluids both in clinical analyses 16. Clinical Chemistry (Volume 2) Atomic Spectrometry in Clinical
and in organic toxicological analysis for forensic purposes. Chemistry
Concentrations of elements in biological material obtained 17. T. Hasegawa and H. Haraguchi, Fundamental Properties of
by this method can be used to interpret results of analyses Inductively Coupled Plasmas, "Inductively Coupled Plasmas in
in cases of suspicion of poisoning by in organic Analytical Atomic Spectrometry," A. Montaser and D. W.
Golightly, Eds., 2nd Edition, VCH Publishers, New York, 1992.
compounds. The ICP-OES method, similarly to other 18. R. F. Browner and A. W. Boorn, Sample Introduction: The
methods, has certain limitations. ICP optical emission Achilles Heel of Atomic Spectroscopy, Anal. Chem. 56, 786A -
spectrometry is now highly rated as a multipurpose 798A (1984).
analysis technique and there are over 2,000 units of ICP- 19. G. W. Dickenson and V. A. Fassel, Emission Spectrometric
OES in use in Japan. It is well regarded as an Detection of Elements at Nanogram per Milliliter Levels Using
Induction Coupled Plasma Excitation, Anal. Chem. 41, 1021 -
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absorption spectrometry and ICP mass spectrometry, and 20. K. J. Fredeen, P. H. Gagne, P. J. Morrisroe, and C. A. Anderau,
its use is expected to expand even further in the future. Alternatives to 27.12 MHz Excitation in an ICP, Paper No. B7.6
presented at XXV CSI, Toronto, 1987.
21. F. E. Lichte and S. R. Koirtyohann, "Induction coupled plasma
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