Plasma-mass spectrometry, inductively coupled

Inductively coupled plasma-mass spectrometry is one of the most sensitive techniques available for trace analysis. Analyte ions produced in the plasma are directed into the inlet of a mass spectrometer, which separates ions by their mass-to-charge ratio. Ions are measured with a sensitive detector that is similar to a photomultiplier tube. The linear range listed in Table 20-4 extends over eight orders of magnitude, and the detection limit is 100-1 000 times lower than that of furnace atomic absorption. 

A problem that is unique to mass spectrometry is isobaric interference in which ions of similar mass-to-charge ratio cannot be distinguished from each other. For example, Ar O found in an Ar plasma has nearly the same mass as e. Doubly 

Matrix effects on the yield of ions in the plasma are important, so calibration standards should be in the same matrix as the unknown. Internal standards can be used if they have nearly the same ionization energy as that of analyte. For example, Tm can be used as an internal standard for U. The ionization energies of these two elements are 5.81 and 6.08 eV, respectively, so they ionize to nearly the same extent in different matrices. Internal standards with just one major isotope provide maximum response. 

Archaeologists use inductively coupled plasma-mass spectrometry to help find the origin of artifacts containing lead. Different locations where lead is mined have different ratios of lead isotopes. Variation occurs because different isotopes of lead are produced by radioactive decay of and Th, whose occurrence varies 

Lead is an impurity in silver. The isotopic composition of the lead measured by inductively coupled plasma-mass spectrometry provides evidence for the origin of the silver because silver mined in each region retains the pattern of lead isotopes from that region. 

3 Inductively Coupled Plasma-Mass Spectrometry Principle 

Inductively coupled plasma (ICP) can also be coupled with mass spectrometry (MS) to become ICP-MS. ICP-MS is a type of mass spectrometry that is capable of analysing of a range of metals and several non-metals at below one part in 10. Further information on ICP-MS is available elsewhere  

Although mainly used for liquid samples where the solution is nebulised into the plasma, solids can be introduced directly in the case of laser-produced plasmas. The microplasma is produced at atmospheric pressure and laser ablation of the sample occurs. Fine particles are taken up by a sdeam of argon for further volatilisation, atomisation and ionisation in the ICP. 

The ICP is the source as in the previous instrument, the ICP-OES. It replaces the usual ion sources that precede the mass analyser in MS. 

The discriminator is the mass analyser of the mass spectrometer. The most commonly employed one for ICP-MS is the quadrupole although others are of course used such as the 

The front-end arrangements used nowadays in conjunction with ICP-MS are tailored to the analytical problem at hand. Sample introduction techniques which 

It is obvious from the history of ICP-MS that the interface is of crucial importance. Within the interface, conditions are converted from the high 

Whilst qualitative survey scans are useful in the preliminary analytical investigations of a problem, the extent to which such signals can be quantified is of greater importance. Unless the sample matrix is simple, 

Although the detection limit of an ICP-MS is about 1 ppt, the device is rather inefficient in the transport of the ions from the plasma to the analyser (interface efficiency of about 1 %). The influence of the ICP-MS sampling cone is still to be worked out. Introduction of organic solvents into an ICP-MS decreases the sensitivity, due to excessive solvent loading of the plasma. 

ICP-MS presents various shortcomings as compared to the requirements of an ideal PS-MS technique (Tables 8.62 and 8.56). Simultaneous detectors, as in ToF-MS or array-detector atomic mass spectra (ADAMS), offer several advantages in terms of sensitivity, precision, LOD (50ppq), resolving power and sample throughput. PS-ToFMS and ICP-ADAMS are still in their infancy. 

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If a sample solution is introduced into the center of the plasma, the constituent molecules are bombarded by the energetic atoms, ions, electrons, and even photons from the plasma itself. Under these vigorous conditions, sample molecules are both ionized and fragmented repeatedly until only their constituent elemental atoms or ions survive. The ions are drawn off into a mass analyzer for measurement of abundances and mJz values. Plasma torches provide a powerful method for introducing and ionizing a wide range of sample types into a mass spectrometer (inductively coupled plasma mass spectrometry, ICP/MS). 

To examine a sample by inductively coupled plasma mass spectrometry (ICP/MS) or inductively coupled plasma atomic-emission spectroscopy (ICP/AES) the sample must be transported into the flame of a plasma torch. Once in the flame, sample molecules are literally ripped apart to form ions of their constituent elements. These fragmentation and ionization processes are described in Chapters 6 and 14. To introduce samples into the center of the (plasma) flame, they must be transported there as gases, as finely dispersed droplets of a solution, or as fine particulate matter. The various methods of sample introduction are described here in three parts — A, B, and C Chapters 15, 16, and 17 — to cover gases, solutions (liquids), and solids. Some types of sample inlets are multipurpose and can be used with gases and liquids or with liquids and solids, but others have been designed specifically for only one kind of analysis. However, the principles governing the operation of inlet systems fall into a small number of categories. This chapter discusses specifically substances that are normally liquids at ambient temperatures. This sort of inlet is the commonest in analytical work. 

Montaudo, G. and Lattimer, R.P., Mass Spectrometry of Polymers, CRC Press, Boca Raton, FL, 2001. Montaser, A., Inductively Coupled Plasma Mass Spectrometry, Wiley, Chichester, U.K., 1998. 

Wangzhao, Z., Advanced Inductively Coupled Plasma Mass Spectrometry Analysis of Rare Elements, Balkema Publishers, 1999. 

To measure trace metals to the levels required in the guidelines involves the use of state-of-the-art instmmentation such as inductively coupled plasma/mass spectrometry (icp/ms). 

Gold is a useflil caUbration standard for this method (see Radioactive tracers). Whereas similar sensitivities can be achieved by inductively coupled plasma mass spectrometry (qv), the latter requires more extensive sample preparation to overcome interference by other metals such as copper (64). 

Numerous methods have been pubUshed for the determination of trace amounts of tellurium (33—42). Instmmental analytical methods (qv) used to determine trace amounts of tellurium include atomic absorption spectrometry, flame, graphite furnace, and hydride generation inductively coupled argon plasma optical emission spectrometry inductively coupled plasma mass spectrometry neutron activation analysis and spectrophotometry (see Mass spectrometry Spectroscopy, optical). Other instmmental methods include polarography, potentiometry, emission spectroscopy, x-ray diffraction, and x-ray fluorescence. 

The very low Hg concentration levels in ice core of remote glaciers require an ultra-sensitive analytical technique as well as a contamination-free sample preparation methodology. The potential of two analytical techniques for Hg determination - cold vapour inductively coupled plasma mass spectrometry (CV ICP-SFMS) and atomic fluorescence spectrometry (AFS) with gold amalgamation was studied. 

The complex of the following destmctive and nondestmctive analytical methods was used for studying the composition of sponges inductively coupled plasma mass-spectrometry (ICP-MS), X-ray fluorescence (XRF), electron probe microanalysis (EPMA), and atomic absorption spectrometry (AAS). Techniques of sample preparation were developed for each method and their metrological characteristics were defined. Relative standard deviations for all the elements did not exceed 0.25 within detection limit. The accuracy of techniques elaborated was checked with the method of additions and control methods of analysis. 

Laser based mass spectrometric methods, such as laser ionization (LIMS) and laser ablation in combination with inductively coupled plasma mass spectrometry (LA-ICP-MS) are powerful analytical techniques for survey analysis of solid substances. To realize the analytical performances methods for the direct trace analysis of synthetic and natural crystals modification of a traditional analytical technique was necessary and suitable standard reference materials (SRM) were required. Recent developments allowed extending the range of analytical applications of LIMS and LA-ICP-MS will be presented and discussed. For example ... 

Inductively coupled plasma-mass spectrometry (ICP-MS) is a multielement analytical method with detection limits which are, for many trace elements, including the rare earth elements, better than those of most conventional techniques. With increasing availability of ICP-MS instalments in geological laboratories this method has been established as the most prominent technique for the determination of a large number of minor and trace elements in geological samples. 

Inductively coupled plasma mass spectrometry was applied to the analysis of six organotin compounds (chlorides of dimethyl-, dibutyl-, trimethyl-, tributyl-, diphenyl-, and triphenyltin). Detection hmits for the six organotins ranged from 24 to 51 pg as tin the dynamic range was over lO, from 1 pg/1 to 10 mg/1 (Inoue Kawabata, 1993). 

Inoue Y, Kawabata K (1993) Speciation of organotin compounds by inductively coupled plasma mass spectrometry combined with liquid chromatography. Journal of the Mass Spectrometry Society of Japan, 41 (4) 245-251. 

Determined by inductively coupled plasma-mass spectrometry of acid digested catalyst samples Calculated from X-ray diffraction peak broadening at (101) foranatase and (110) formtile TiOa Mean particle diameter measured from transmission electron microscopy pictures of gold catalysts... 

Dobney AM. Mank AJG, Conneely P, Grobecker K-H, de Roster CG (2000) Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) as a tool for studying heterogeneity within polymers. Submitted for publication... 

Moens L, Verreft P, Boonen S, Vanhaecke F and Dams R (1995) Solid sampling electrothermal vaporization for sample introduction in inductively coupled plasma atomic emission spectrometry and inductively coupled plasma mass spectrometry. Spectrochim Acta 508 463-475. Mooijman KA, In t Veld PH, Hoekstra JA, Heisterkamp SH, Havelaar AH, Notermans SHW, Roberts D, Griepink B, Maier E (1992) Development of Microbiological Reference Materials. European Commission Report EUR 14375 EN, Community Bureau of Reference, Brussels. 

Method abbreviations D-AT-FAAS (derivative flame AAS with atom trapping), ETAAS (electrothermal AAS), GC (gas chromatography), HGAAS (hydride generation AAS), HR-ICP-MS (high resolution inductively coupled plasma mass spectrometry), ICP-AES (inductively coupled plasma atomic emission spectrometry), ICP-MS (inductively coupled plasma mass spectrometry), TXRF (total reflection X-ray fluorescence spectrometry), Q-ICP-MS (quadrapole inductively coupled plasma mass spectrometry)... 

Larsen EH, Knuthsen P, Hansen M (1999) Seasonal and regional variations of iodine in Danish dairy products determined by inductively coupled plasma mass spectrometry. J Anal At Spectrom 14 41-44. 

Chudzinska, M. and Baralkiewicz, D. (2010). Estimation of honey authenticity by multielements characteristics using inductively coupled plasma-mass spectrometry (ICP-MS) combined with chemometrics. Food Chem. Toxicol. 48, 284-290. 

In modern times, most analyses are performed on an analytical instrument for, e.g., gas chromatography (GC), high-performance liquid chromatography (HPLC), ultra-violet/visible (UV) or infrared (IR) spectrophotometry, atomic absorption spectrometry, inductively coupled plasma mass spectrometry (ICP-MS), mass spectrometry. Each of these instruments has a limitation on the amount of an analyte that they can detect. This limitation can be expressed as the IDL, which may be defined as the smallest amount of an analyte that can be reliably detected or differentiated from the background on an instrument. 

In contrast to thermal ionization methods, where the tracer added must be of the same element as the analyte, tracers of different elemental composition but similar ionization efficiency can be utilized for inductively coupled plasma mass spectrometry (ICPMS) analysis. Hence, for ICPMS work, uranium can be added to thorium or radium samples as a way of correcting for instrumental mass bias (e g., Luo et al. 1997 Stirling et al. 2001 Pietruszka et al. 2002). The only drawback of this approach is that small inter-element (e g., U vs. Th) biases may be present during ionization or detection that need to be considered and evaluated (e.g., Pietruszka et al. 2002). 

Multiple-collector inductively coupled plasma mass spectrometry (MC-ICPMS) combines sector-field ICPMS with a multiple collector detector system and has recently emerged as an alternative to TIMS for precise U-Th isotope measurement. The full potential of MC-ICPMS has yet to be realized. Yet despite this, its performance in high precision isotope measurement already challenges and, in some cases, surpasses that ever achieved by TIMS (e.g., Lee and Halliday 1995 Blichert-Toft and Albarede 1997). 

Becker JS, Pickhardt C, Dietze H-J (2000) Laser ablation inductively coupled plasma mass spectrometry for the trace, ultratrace and isotope analysis of long-lived radionuclides in solid samples. Inti J Mass Spectrom 202 283-297... 

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