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Table of content

Objective.1

Introduction2

Background of ICP-AES....3

Principles.4

Instrumentation.5

Sample preparation6-7

Applications of ICP-AES8

Applications of ICP-AES to field of study and recommendation.

..9

Reference 10


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Objective

1. Discuss what Inductive Coupled Plasma- Atomic Emission Spectroscopy.

2. The theory that surrounds this technique

3. Explain how it is Applied in society

4. The advantage of using this technique

5. Recommendation on how to improve this technique


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Introduction

Inductively coupled plasma-atomic emission spectrometry (ICP-AES) is a spectrometric

technique. This is done base on the fact that excited electrons emit energy at a given wavelength

when they return to their unexcited state. Each element emits energy of specific wavelengths, but

typically only one wavelength per element is chosen for the analytical procedure. It is an

established analytical method in geochemistry. Its applications have a wide range, very cost-

efficient and ideal for geochemical projects requiring a large number of samples. Using this

technique has advantages of a very high plasma-temperature is utilize and many spectral lines

for the elements can be produced, with atom and ion lines available for even the most refractory

elements. Traditionally problematic molecular interferences are limited because chemical bonds

do not survive the high temperatures of the plasma. In analyzing rock-samples all major elements


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and most of the trace elements can be measured by this technique, except Oxygen, Nitrogen, C,

the halogen and inert gas elements. After separation of major and some trace elements it is also

possible to measure the rare earth elements. Rubidium and cesium are difficult to measure at

trace levels; they are too easily ionized in the high temperature of the plasma. The elements

Uranium, Thorium, Tungsten and Thallium are normally below the detection limit.

The instrument is calibrated with multi-element standard-solutions. In this matrix effects

are a minor problem in ICP-AES, except for elements in complex matrices which are generally

calibrated with natural samples. Good detection limits are expected because of low background

signals. Linearity of calibration lines is an essential tool four routine analysis that permits

simultaneous measurements of major- and trace elements which it ensures.

Back ground of ICP-AES

ICP-AES has been widely used since the 1970's for the simultaneous multi-element

analysis of environmental and biological samples after dissolution. Inductively Coupled Plasma-

Atomic Emission Spectrometry (ICP-AES) is one of the most common techniques for elemental

analysis. Its high specificity, multi-element capability and good detection limits result in the use

of the technique in a large variety of applications.

Inductively Coupled Plasma Emission Spectrometry (ICP-ES) instrumentation came about in

the 1970s. Previously, trace metals were typically analyzed using colorimetric techniques, which

were both cumbersome and subject to interferences, or flame atomic absorption techniques,

which, although almost interference free, were labor intensive owing to their one-element-at-a-


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time analytical mode. Even the furnace atomic absorption technique, for years the standard

bearer of low-level trace metal analysis, is giving way to axial and radial viewed ICP-AES

techniques. Now, ICP-AES has become an affordable and well-established multielement

analytical method.

ICP optical systems became popular in the 1980s due to their decreased cost, lower time

investment during analysis, and labor saving advantages. Inductively Coupled Plasma-Atomic

Emission Spectroscopy (ICP-AES) is one of several techniques available in analytical atomic

spectroscopy. ICP-AES utilizes plasma as the atomization and excitation source. Plasma is an

electrically neutral, highly ionized gas that consists of ions, electrons, and atoms. The sun,

lightning, and the aurora borealis are examples of plasmas found in nature. The energy that

maintains analytical plasma is derived from an electric or magnetic field; they do not

burn.Most analytical plasmas operate with pure argon or helium, which makes combustion

Principles

ICP-AES is an emission spectophotometric technique is done by exploiting the fact that

excited electrons emit energy at a given wavelength as they return to ground state. The

fundamental characteristic of this is that elements will emits energy at specific wavelength.

Although each element emits energy at multiple wavelengths, in the ICP-AES technique it is

most common to select a single wavelength or a very few for a given element. The intensity of

the energy emitted at the chosen wavelength is proportional to the amount of that element in the

analyzed sample. Thus, by determining which wavelengths are emitted by a sample and by

determining their intensities, the analyst can quantify the elemental composition of the given

sample relative to a reference standard.


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ICP-AES analysis requires a sample to be in solution. Thus, interstitial waters can be

analyzed simply, requiring only dilution in most cases. Sedimentary rocks and sediments should

be dissolved. This can be achieved either by a combined acid attack employing HF, HNO3, and

HCl acids. HF is highly reactive in nature and the acid attack is not able to generate consistent

and reliable data for Si because it volatilizes in the presence of HF. The acid digestion procedure

also often results in incomplete analysis of refractory elements such as Ti, Cr, and Zr because

their host minerals are often difficult to dissolve. There is the flux-fusion approach which is

employed on board the Resolution for several reasons. It is safer because HF is not involved, it is

a complete dissolution technique, allowing determination of all elements, including Si and the

refractoryelements, the resultant solutions are similar in composition because they aredominated by the presence of the LiBO2 flux; and the solutions are stable in dilute HNO3 acid.

Instrumentation

The ICP AES is composed of the sample introduction system, the torch assembly, and the

spectrometer. A peristaltic pump delivers an aqueous or organic sample into a nebulizerwhere it

is changed into mist and introduced directly inside the plasma flame. The sample immediately

collides with the electrons and charged ions in the plasma and is itself broken down into

charged ions. The various molecules break up into their respective atoms which then

lose electrons and recombine repeatedly in the plasma, giving off radiation at the

characteristic wavelengths of the elements involved. The torch unit of an ICP is used to create

and sustain a plasma. A plasma is an electrically conducting gaseous mixture containing enough

cations and electrons (though the plasma has a neutral charge overall) to maintain the

conductance. This unit uses an induction coil to produce a magnetic field. The induction coil is
http://en.wikipedia.org/wiki/Peristaltic_pumphttp://en.wikipedia.org/wiki/Nebulizerhttp://en.wikipedia.org/wiki/Ionshttp://en.wikipedia.org/wiki/Electronhttp://en.wikipedia.org/wiki/Wavelengthhttp://en.wikipedia.org/wiki/Peristaltic_pumphttp://en.wikipedia.org/wiki/Nebulizerhttp://en.wikipedia.org/wiki/Ionshttp://en.wikipedia.org/wiki/Electronhttp://en.wikipedia.org/wiki/Wavelength


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wrapped two or three times around the ICP torch and has water flowing through it for cooling

purposes.

All ICPs have a capacitor bank that is continuously tuned to match the plasmas

inductance. Although the RF power supply maintains the plasma, a tesla coil is used to ignite the

plasma through the generation electrons and ions that couple with the magnetic field. Most ICP-

AES instruments are designed to detect a single wavelength at a time (monochromator), but,

seeing as elements emit at different wavelengths, it is desirable to detect more than one

wavelength at a time. This can be done by the use of a polychromator. The polychromator is a

spectrometer that is designed to capture emissions of several wavelengths simultaneously.

Detection limits typically range from parts per million (ppm) to parts per billion (ppb), although

depending on the element and instrument, can sometimes achieve less than ppb detection.

Sample preparation

Solid and gaseous samples that are not put into solution before introduction to the

ICP generally need little preparation, but rather require special sample introduction methods and

hardware. The basic goals of sample preparation for ICP-OES are to put the sample into solution,

stabilize the sample-containing solution especially if low concentrations of analyte are present,

the analyte concentration fall within the working range of the instrument through dilution or pre-

concentration, and ensure that the sample-containing solution can be nebulized in a reproducible

manner. The third goal may be difficult for samples that contain both very high and very low

concentrations of analyte species. In these cases, it may be necessary to prepare two different

dilutions of the sample. Solid samples are generally dissolved in acids before introduction into


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the ICP. This process, called acid digestion, quite often requires heating the digestion solution,

which contains the sample and acid(s), with a hot plate or a microwave oven. Liquid samples that

contain particulates may also require a digestion procedure to dissolve the particulates or

filtration to remove the particulates if the particulates do not contain significant amounts of

analyte. Some solids that are particularly difficult to dissolve may require a fusion reaction, in

which the sample is reacted with a compound such as lithium metaborate and then dissolved in

an appropriate matrix. Organic-based liquid samples may require dilution with an appropriate

organic solvent to make the sample easier to nebulize.

The possibility of precipitation of the analyte may dictate the selection of an acid to prepare a

sample containing silver as an analyte since the silver could precipitate from the solution as

AgCl. In the early days of ICP-AES, it was usually suggested that hydrofluoric acid not be used

for digestion procedures since HF can degrade the glass and quartz components of the sample

introduction system and torch. This limitation has been nearly eliminated by the availability of

HF-resistant sample introduction systems and torches for most modern ICP-AES instruments.

Preparation of standards is done by dissolving high-purity metals or salts with high-purity acids

or other appropriate reagents and then diluting to obtain the desired concentrations. Also

available from a wide variety of vendors are standard solutions that can be diluted as necessary

by the analyst. When preparing mixed standards, i.e., standards containing a known

concentration of more than one element, one must make sure that the elements of interest are

compatible with the other species in the solution so that precipitation of the standard elements

does not occur. An important concept related to sample preparation and interference correction is

that of matrix matching. Matrix matching involves preparing solutions whose major concerns

match those of another solution. While matrix matching certainly involves matching the solvents,


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it also involves matching the concentrations of acids and other major solutes. For example, if one

wanted to matrix match a standard to a steel sample solution containing 10% Fe, he or she would

add enough iron to the standard so that the iron concentration of the standard matched that of the

sample. When preparing the blank solution to be used in the standardization process, it is

recommended that the blank be matrix matched with the standard solution(s) to be used. For

analysis of most common aqueous samples, this would usually involve adding a specified

amount of acid to some deionized water. Other than using the same solvent for the standard and

samples, it is usually not necessary to matrix match the standards and samples exactly, except as

a last resort for correcting for interferences.

Application of ICP-AES

ICP-AES is used in minerals processing to provide the data on grades of various streams, for the

construction of mass balances. Other examples of the application include the determination of

metals in wine, arsenic in food and trace elements bound to proteins.

In 2008, the technique was used at Liverpool University to demonstrate that a Chi-

Rho amulet found in Shepton Mallet and previously believed to be among the earliest evidence

ofChristianity in England only dated to the nineteenth century.

ICP-AES is often used for analysis of trace elements in soil, and it is for that reason it is often

used in forensics to ascertain the origin of soil samples found at crime scenes or on victims etc.

Taking one sample from a control and determining the metal composition and taking the sample
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obtained from evidence and determine that metal composition allows a comparison to be made.

While soil evidence may not stand alone in court it certainly strengthens other evidence.

ICP-AES is used formotor oil analysis. Analyzing used motor oil reveals a great deal about how

the engine is operating. Parts that wear in the engine will deposit traces in the oil which can be

detected with ICP-AES. ICP-AES analysis can help to determine whether parts are failing. In

addition, ICP-AES can determine what amount of certain oil additives remain and therefore

indicate how much service life the oil has remaining. ICP-AES is also used during the production

of motor oils (and other lubricating oils) for quality control and compliance with production and

industry specifications.

Application to field of study and Recomendation

Research reveals more information regarding the roles and behaviors of trace elements in

biological system and so ICP-AES has become an important tool in the area of biological and

clinical applications. Determinations by ICP-AES of essential, toxic and therapeutic trace

elements are important in the medical research laboratories as well as in the clinical and forensic

lab environments. Significant concern regarding trace element determinations in the biological

and clinical fields is the contamination of samples prior to their analysis. The use of surgical

equipment, such as scalpels, needles, scissors, and forceps, often contaminates the sample with

trace quantities of the very elements being determined in the sample. For this reason, appropriate

equipment should be used to collect, process and store biological and clinical samples before
http://en.wikipedia.org/wiki/Motor_oilhttp://en.wikipedia.org/wiki/Motor_oil


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analysis by ICP-OES. Many biological and clinical samples are either too small or contain

elemental concentrations too low for ICP-OES analysis using conventional pneumatic sample

introduction. In these cases, it is often necessary to turn to alternate sample introduction

techniques such as ultrasonic nebulization, electrothermal vaporization, or hydride generation, or

preconcentration techniques such as ion exchange or solvent extraction. Examples of ICP-OES

analyses of biological and clinical samples include determinations of Cr, Ni and Cu in urine; Al

in blood; Cu in brain tissue; Se in liver; Cr in feces; Ni in breast milk; B, P and S in bone; and

trace elements in oyster and tuna tissues.

References

1. http://www-odp.tamu.edu/publications/tnotes/tn29/technot2.htm

2. http://minerals.cr.usgs.gov/gips/na/5process.html

3. http://www.perkinelmer.com/Catalog/Category/ID/ICP%20Optical%20Emission

%20ICPOES

4. http://www.ecn.nl/docs/society/horizontal/hor_desk_19_icp.pdf
http://www-odp.tamu.edu/publications/tnotes/tn29/technot2.htmhttp://minerals.cr.usgs.gov/gips/na/5process.htmlhttp://www.perkinelmer.com/Catalog/Category/ID/ICP%20Optical%20Emission%20ICPOEShttp://www.perkinelmer.com/Catalog/Category/ID/ICP%20Optical%20Emission%20ICPOEShttp://www.ecn.nl/docs/society/horizontal/hor_desk_19_icp.pdfhttp://www-odp.tamu.edu/publications/tnotes/tn29/technot2.htmhttp://minerals.cr.usgs.gov/gips/na/5process.htmlhttp://www.perkinelmer.com/Catalog/Category/ID/ICP%20Optical%20Emission%20ICPOEShttp://www.perkinelmer.com/Catalog/Category/ID/ICP%20Optical%20Emission%20ICPOEShttp://www.ecn.nl/docs/society/horizontal/hor_desk_19_icp.pdf


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