ICPMS原理介绍 英文版.pdf

ICP-MSInductively Coupled PlasmaMass SpectrometryA PrimeriTable of Contents ICP-MS PrimerSection 1 Introduction to ICP-MS1History and Development of ICP-MS2Agilent Technologies-History in ICP-MS4Section 2 Fundamentals of ICP-MS5Overview of ICP-MS Major Components6Hardware Design8Section 3 Control of Interferences in ICP-MS27Introduction28Collision/Reaction Cell(CRC)ICP-MS30Octopole Reaction System30Section 4 Sample Preparation and Contamination Control37Section 5 Extending the Capabilities of ICP-MS41Liquid Sample Introduction42Laser Ablation45Other Solids Analysis Techniques47 iiSection 6 Hyphenated ICP-MS49GC-ICP-MS52LC(IC)-ICP-MS56CE-ICP-MS60Section 7 Applications of ICP-MS63Environmental64Food and Agriculture66Semiconductor67Clinical and Pharmaceutical69Geological70Nuclear72Forensic72Chemical,Petrochemical74Section 8 Operating Costs,Maintenance and Diagnostics 75Section 9 Legislated ICP-MS Methods79Section 1 Introduction to ICP-MS2History and Development of ICP-MSBeginningsDr Alan Gray of Applied Research Laboratories in Luton,UK,conducted much of the early research work that led to the commercial development of ICP-MS instrumentation.Initially working with a capillary direct current(DC)arc plasma coupled to a quadrupole mass spectrometer,he published early results and the first mass spectra acquired from a plasma,in a paper in 1975 1.This work stimulated research into the use of inductively coupled radio frequency(RF)plasmas(ICPs),with some of the key developments taking place in the lab of Velmer Fassel at Iowa State University incollaboration with Dr Gray in 1978.Inductively Coupled Plasma Mass Spectrometry(ICP-MS)was developed as a commercial analytical techniquein the early 1980s and has since been applied to thedetermination of trace,minor and major elements in almostevery analytical field.Strengths of the technique include:Wide elemental coverage-virtually all elementscan be measured by ICP-MS,including alkali andalkaline earth elements,transition and other metals,metalloids,rare earth elements,most of the halogensand some of the non-metals Performance-high sensitivity and low backgroundsignals combine to give very low detection limits(sub-ng/L parts-per-trillion(ppt)in most cases)Fast analysis times with a high speed scanningquadrupole analyzer,measurement of a full suite of elements takes only about 4 minutes per sample Wide analytical working range up to 9 orders in a single acquisition Isotopic information Excellent chromatographic detectorIn the range of atomic spectrometry techniques used inanalytical laboratories,ICP-MS holds a unique position byvirtue of its speed,sensitivity,dynamic range and elemental coverage,see Table 1.It can be considered as a viablealternative to ICP-Optical Emission Spectroscopy(OES)(also known as Atomic Emission Spectroscopy or AES)for fast measurement of higher concentration elements(g/L to mg/L or parts-per-billion to parts-per-millionconcentrations).At the same time,ICP-MS rivals or,inmany cases,exceeds the detection capability of GraphiteFurnace Atomic Absorption Spectroscopy(GFAAS)for thedetermination of trace and ultra-trace elements(ng/L or ppt concentrations).ICP-MS can measure a full suite of elements in a singlemulti-element acquisition,accepts almost any sample typeand also provides isotopic information.One of the fastestgrowing areas of ICP-MS is in speciation measurement:thecombination of chromatographic techniques with ICP-MSas a detector to determine the chemical form of elements in the sample.These capabilities help to explain thewidespread acceptance of ICP-MS across all industry types,and confirm the status of ICP-MS as the premier techniquefor trace metals measurement.Over the next few years,ICP-MS will continue to grow at the expense of other techniques listed in Table 1,asdemands for more sensitive measurement with higherproductivity continue to increase.3Hydride forming elements(As,Se,Tl,Pb,Bi,Sb,Te)ppt to ppbSensitive,few interferencesSingle element,slow,complexICP-OESMost metals and some non-metalsmid ppb tomid ppmRapid,multi-elemental,high TDS toleranceComplex interferences,relatively poor sensitivityTECHNIQUEMETALSAPPROX DL RANGEADVANTAGESDISADVANTAGESICP-MSMost metals and non-metalspptRapid,sensitive,multi-element,wide dynamicrange,good control of interferencesLimited total dissolvedsolids(TDS)tolerance GFAAMost metals(commonly Pb,Ni,Cd,Co,Cu,As,Se)pptSensitive,few interferencesSingle element technique,limited dynamic rangeCold VaporMercuryHgpptSensitive,simple,few interferencesSingle element,slowTable 1.Comparison of atomic spectrometry techniquesIntroduction to ICP-MSFirst Commercial InstrumentsAn important publication by Houk et al.2 in 1980demonstrated the possibilities offered by the ICP-MStechnique,and the first commercial systems followed in the early 1980s.These systems were derived from parts of two existingtechnologies the argon ICP,already in use in ICP-OES,and the quadrupole mass spectrometer,then being appliedin fields such as Gas Chromatography Mass Spectrometry(GC-MS)and residual gas analysis.Some changes werenecessary to allow the ICP to operate in physical contactwith the grounded spectrometer interface,but thecharacteristics of these existing technologies were wellmatched and the performance of the first systems wasimpressive.Although the early ICP-MS systems wereexpensive,large,complex,had limited automation andtended to suffer from significant signal drift,the obviousbenefits of a multi-element technique with low limits ofdetection and a simple mass spectrometric data output(including isotope ratio information)led to acceptance of the fledgling technique,particularly among those involvedin research and geological applications.Application of thetechnique in laboratories where reliability,stability andautomation were a high priority,led to rapid improvement of the commercial instruments and ultimately to the small,reliable,stable and highly automated systems availabletoday.ICP-MS systems with magnetic sector and time-of-flight mass analyzers have also been commercialized,butthe quadrupole-based systems remain the configuration ofchoice by a very wide margin.Since the first commercialICP-MS systems were launched,major developments haveoccurred in sample introduction,plasma efficiency,iontransmission,interference removal and dynamic range.Evenso,the major components of a modern ICP-MS instrumentcan be traced directly back to the earliest systems,illustrating how inspired the original concept was.References1 Gray,A.L.,1975,Analyst,100,289-2992 Houk,R.S.,Fassel,V.A.,Flesch,G.D.,Svec,H.J.,Gray,A.L and Taylor,C.E.,1980,Anal.Chem.,52,2283-2289Hydride AA4It incorporated a passive type(no scanning voltage used)CRC cell an Octopole Reaction System(ORS)for simpleremoval of interferences in complex matrices.Sidereactions between cell gases and the analyte wereeliminated with the ORS using only pure He in collisionmode made possible by the narrow ion energydistribution delivered by the ShieldTorch System.Further development in the field of CRC technology resulted in the introduction in 2003 of a new,highsensitivity reaction cell system(7500cs)designed forsemiconductor and research use.In 2004 Agilent launcheda successor to the 7500c,the 7500ce,with highersensitivity and designed for the analysis of high matrixsamples in environmental,clinical and other key industries.In 2005,Agilent introduced an optional 3rd cell gas line tofurther expand the applicability of the ORS to researchapplications.With the analytical advantages of the ORSrecognized by analysts worldwide it has grown inpopularity:by 2005 over 85%of all Agilent 7500 Seriessold were ORS systems.HP 4500-the first benchtop ICP-MS.Hewlett-PackardAnalytical Instruments Division formed part ofAgilent Techologies in 1999.Agilent Technologies-History in ICP-MSFirst Benchtop ICP-MSIn the early 1990s,a joint venture between Hewlett-Packard and Yokogawa Electric in Japan created YokogawaAnalytical Systems.Yokogawa had introduced the worldsfirst computer controlled ICP-MS in 1987 in Japan.Bycombining Yokogawas innovative developments in ICP-MSwith Hewlett-Packards expertise in mass production andminiaturization of quadrupole mass spectrometers,the HP4500 ICP-MS was created and introduced in 1994.The4500 was the first benchtop ICP-MS and includednumerous technological advances including ShieldTorchtechnology,off-axis ion lens,all solid state RF generator,Peltier cooled spray chamber and the highest frequencyquadrupole of any ICP-MS.The 4500 dominated thedemanding semiconductor market worldwide because of the ability of the ShieldTorch System to reduce argon-based interferences and allow measurement of K,Ca andFe at ppt levels.The robustness and ease of use of the4500 also ensured its adoption into routine environmentallaboratories worldwide.By 1998,the 4500 was the#1selling ICP-MS worldwide,with over 750 units shipped by 1999.Contributing to success of the 4500 model in the environmental market were the Integrated SampleIntroduction System(ISIS),and Intelligent Sequencing,which automated many of the sample preparation andquality assurance/quality control(QA/QC)requirements of the commercial laboratory.Era of Collision/Reaction Cell SystemsAgilent began investigating the performance of collision/reaction cells(CRC)in ICP-MS in 1997.At the time the firstcommercial CRCs were launched in the late 1990s,Agilentwere concentrating their development on a system suitablefor routine analysis,especially for unknown samples.Theresult was the Agilent 7500c introduced in January 2001.Agilent 7500 Series ICP-MSSection 2 Fundamentals of ICP-MSOverview of ICP-MS Major ComponentsAn ICP-MS instrument consists of several distinct parts:Sample introduction Ion generation in the ICP Plasma/vacuum interface Ion focusing Ion separation and measurementSample introduction:The sample is typically introducedinto the Inductively Coupled Plasma(ICP)as an aerosol,produced by passing the liquid sample through a simplepneumatic nebulizer.Larger aerosol droplets are removedfrom the gas stream by a spray chamber,and the remainingsmaller droplets are swept into the central channel of theargon plasma.The Agilent 7500 Series is fitted with aScott-type double pass spray chamber manufactured fromhigh-purity quartz.Spray chamber temperature is preciselymaintained with a thermoelectric(Peltier)device to preventsignal drift caused by large changes in room temperatureand also to reduce solvent loading on the plasma.Thisreduced solvent loading leads to a higher plasmatemperature,reducing oxide interferences,and assisting in matrix decomposition.Ion generation in the ICP:The sample aerosol is passedinto the plasma,which is generated in a stream of argon(Ar)contained in a quartz tube or torch.The torch islocated in the center of a cooled copper coil,through which a high power,high frequency electric current ispassed.The intense magnetic field created by the electriccurrent causes collisions between free electrons and Aratoms,producing ions and more electrons,until a stable,high temperature plasma is formed.The high frequencycurrent is produced by a radio frequency(RF)generatoroperating at powers up to 1600W.While two RFfrequencies are approved for ICPs,40.68 MHz and 27.12 MHz,the latter has been shown to result in higherplasma temperatures and is used in most modern and allAgilent ICP-MS instruments.The very high temperature ofthe plasma(up to 10,000K maximum and around 7,500K in the central channel)means that the aerosol droplets are rapidly dried,decomposed,vaporized and atomized,then ionized by the removal of one electron from eachatom.The resulting ions,which are formed within about10ms of the original aerosol droplet entering the back ofthe plasma,are present at the highest level at about 7mmfrom the end of the load coil,which is where thespectrometer interface is positioned.6+Figure 1:Schematic representation of processes in ICP-MS from sample introduction to mass analysisLiquidSampleSolidSampleAerosolParticleMoleculeAtomIonMass SpectrumMassSpectrometerSprayChamberPlasmaNebulizer(liquid)Laser(solid)GaseousSampleNEBULIZATION DESOLVATION VAPORIZATION ATOMIZATION IONIZATION MASS ANALYSISFundamentals of ICP-MSInterface:The positively charged ions that are produced inthe plasma are extracted into the vacuum system,via a pairof interface“cones”.The cones are essentially metal plateswith central orifices through which the ions pass.Smallorifices are used,typically 1mm diameter or less,to maintainthe high vacuum in the mass spectrometer region.Ion focusing:Electrostatic lenses keep the ions focused in a compact ion beam as they pass through the vacuumsystem to the final chamber,where the mass spectrometer(MS)and detector are housed.The ion lenses perform asecond,essential,function of separating the ions from thephotons and residual neutral material.Agilent uses a high-transmission off-axis or Omega lens arrangement thatseparates the positively charged ions from the photons andneutral particles,which would otherwise reach the detectorand increase random background noise.Mass spectrometer:Three different types of massanalyzers have been used with ICP-MS;these are quadrupole,magnetic sector,and time-of-flight analyzers.By far themost common mass analyzer used in ICP-MS,and the oneemployed on the Agilent 7500 Series,is the quadrupole.Thequadrupole uses a combination of DC(direct current)and AC(alternating current)electrical fields to separate ions based ontheir mass to charge ratio(m/z).Since the plasma producesalmost exclusively singly-charged ions,the mass/charge ratiois equal to the mass of the ion,making the spectrum verysimple to interpret.The ratio of the DC and AC electrical fieldsis fixed but the voltages can be changed.For a given voltagesetting,only one m/z is stable and the quadrupole scans rapidlyacross the mass range(2-260 amu),passing each mass ofinterest sequentially to the electron multiplier(EM)detector.Ion detection:The electron multiplier detects each ion as itexits the quadrupole.The detector electronics count andstore the total signal for each mass(m/z),creating a massspectrum(Figure 2).The spectrum that is produced providesa simple and accurate qualitative representation of thesample.The magnitude of each peak is directly proportionalto the concentration of an element in a sample;quantitativeresults are produced by comparing signal intensities to thosegenerated by calibration standards.7Figure 2:Full scan spectrumof spiked cinnamon extractshowing relative abundancesof elemental constituents.Enlargement shows isotopesof lead,present at 10 ppb.1 Spectrum No.1 152.427 sec:spectrum.d/Tune#1 Count Linear1 Spectrum No.1 152.427 sec:spectrum.d/Tune#1 Count LinearHardware DesignThe main components of a typical commercial ICP-MSinstrument see Figure 3,are outlined in the followingsections,with a brief discussion of the key parameters that affect the operation and performance of each part of the system.Sample Introduction-Overvie