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A Comparison between ICP –MS and ICP – OESSpectrometric Techniques

ICP Plasma Source

Both ICP – OES and ICP – MS are considered the most advanced level and rapidanalysis techniques available for estimation of elements at trace and ultra trace levels.Both the techniques are based on atomisation and ecitation of the sample in theplasma source. !n understandin" of the plasma ecitation source is essential for

appreciatin" the t#o techniques.

Plasma Excitation Source

Plasma also termed as the fourth state of matter is the most abundant form of matter inthe universe because ma$ority of stars comprise of matter in the plasma state. It containsfree ionised atoms and electrons. It is possible to confine it into a small volume in thelaboratory and use it as a source for atomisation and ecitation of samples introducedinto it as a liquid aerosol.

%he ICP source comprises of three concentric tubes made of quart& for ar"on andsample aerosol introduction. !r"on "as spirals tan"entially up#ards and the "as from

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the nebuliser #ith sample moves inside the inner sample tube. Plasma is "eneratedabove the inlet $et by means of radio frequency ener"y applied to the coil. %he plasmaattains a temperature of '((() – *((() + #hich is sufficient to ecite the sampleelements. %he detection of elements beyond the source is based on measurement ofli"ht emission by elements ,ICP – OES- or by separation of ions on the basis of mass to

char"e ,m&- ratio ,ICP – MS-

ICP – OES

ICP – OES also referred to as ICP – !tomic Emission Spectroscopy ,ICP – !ES- isolatesthe emitted li"ht by the source into discrete component #avelen"ths usin" a diffraction"ratin".

%he sensitivity of the technique is in direct proportion to the li"ht intensity emitted at each#avelen"th and simultaneous analysis systems afford analysis of up to '( elements in a

sin"le run. /ar"e linear dynamic ran"e permits detection levels bet#een sub ppm toabout 0((( ppm levels in less than a minute. It is a robust technique affordin" analysis inpresence of up to 1(2 dissolved solids.

ICP – MS

ICP – MS ta3es advanta"e of ecitation leadin" to ioni&ation of elements as #ell asseparation of ionised species by quadrupole mass separation and detection by electronmultiplier system. In addition to estimation of the elements it is also capable of providin"isotope ratio studies.

ICP – MS can achieve hi"her linear dynamic ran"e up to #hich permitsdetermination at concentration levels ran"in" from sub4ppt to ppm levels. ICP – MScannot be used for samples havin" total dissolved solids as these effect nebuliser andefficiency. Capabilities of ICP4 MS have been further eploited by couplin" #ith /C toconduct speciation studies on metals bound to proteins and other or"anic molecules.

ICP – MS systems are more epensive than ICP – OES systems and operational cost isalso hi"her due to hi"her consumption of ar"on "as but the cost factor is offset by thedistinct advanta"es offered by the technique.

 ! subsequent article #ill provide "uidance on selection of elemental analysis techniquesas per your analysis requirements.